IMSUB
Supported, behaves as documentedCategory: Engineering · Last tested 2026-09-01
Real compatibility results for the IMSUB function: executed in Excel for the web, Google Sheets and LibreOffice Calc, with desktop Excel behavior from Microsoft’s official documentation (we do not run desktop Excel — Excel for the web is a different application and is executed separately). Syntax and links to that documentation are below.
Support matrix
| Engine | Documented | Live-tested | Verdict |
|---|---|---|---|
| Excel (desktop) | Yes | No — documented only | n/a |
| Excel for the web | — | Yes (recalc, 2026-09-01) | Supported, behaves as documented |
| Google Sheets | Yes | Yes (Drive import, 2026-08-31) | Supported, behaves as documented |
| LibreOffice Calc | Yes | Yes (25.8.7.3, 2026-08-31) | Supported, behaves as documented |
LibreOffice version history
We executed the same test cases under each LibreOffice release to show exactly when IMSUB’s support changed — not documentation claims, real results.
| LibreOffice version | Verdict | Tested |
|---|---|---|
| 24.2.0.3 | Supported, behaves as documented | 2026-08-31 |
| 24.8.7.2 | Supported, behaves as documented | 2026-08-31 |
| 25.2.0.3 | Supported, behaves as documented | 2026-08-31 |
| 25.8.7.3 | Supported, behaves as documented | 2026-08-31 |
Executed test cases
Excel for the web (executed 2026-09-01 via OneDrive recalculation)
These values come from Excel for the web, not from desktop Excel. They are two different implementations of the calculation engine, and this run measured only the web one: the corpus was uploaded to OneDrive as .xlsx, recalculated by Excel for the web on open, and downloaded again for readback. Excel for the web is a rolling service with no pinnable version, so the run is identified by its date. Where a value here disagrees with the Expected column — which is Microsoft’s documentation of the desktop product — we cannot tell you whether the web engine diverges from the desktop one or the documentation is wrong about both, because we do not run desktop Excel.
| Formula | Description | Result | Expected | Verdict |
|---|---|---|---|---|
| =IMSUB("13+4i","5+3i") | Microsoft's documented worked example: the difference of two complex numbers | 8+i | 8+iProvenanceMicrosoft publishes '=IMSUB("13+4i","5+3i")' with the result 8+i. Derived from the identity the page renders as an image, (a+bi) - (c+di) = (a-c) + (b-d)i: 13-5 = 8 and 4-3 = 1. Exact integer arithmetic. The result is one of the two published Microsoft strings in which an imaginary coefficient of exactly 1 is printed as "i" with no digit -- the rule that the IMSQRT("-1") case in this same batch shows LibreOffice only got right from 25.2 onwards. EXCEL'S COMPLEX-STRING FORMAT, which this corpus derives rather than assumes: a result is rendered as the real part, then the sign, then the imaginary coefficient followed by the suffix, with each part printed to at most 15 significant digits and trailing zeros stripped; a zero real part is omitted entirely, a zero imaginary part reduces the result to a bare real number, and an imaginary coefficient of exactly 1 or -1 prints as "i" / "-i" with no digit. That rule was written as a formatter in Python by batch D and validated against seven independently published Microsoft strings (IMCOS, IMCOSH, IMCOT, IMCSC, IMCSCH, IMEXP, IMLN); batch E re-ran that validation and then extended it, reproducing THIRTEEN MORE published Microsoft strings byte for byte (IMLOG10, IMLOG2, IMPOWER, both IMPRODUCT examples, IMSEC, IMSECH, IMSIN, IMSINH, IMSQRT, IMSUB, IMSUM, IMTAN) before predicting anything -- twenty published strings in all. ONE REFINEMENT BATCH E HAD TO MAKE: batch D fed the formatter the EXACT value computed at 40 digits, which happened to render identically to the IEEE double for all seven of its strings. That is not true here. A spreadsheet engine holds a double, not the exact value, and two of this batch's published strings only come out right if the derivation rounds to the nearest double BEFORE formatting: IMPOWER("2+3i",3) is exactly -46+9i in exact arithmetic but Microsoft publishes -46+9.00000000000001i, which is what exp(3*ln(2+3i)) gives in double precision; and IMSEC("4+3i") has an exact real part of -0.06529402785794704644..., whose 15-digit rounding ends ...47, while the correctly-rounded double -0.065294027857947051 rounds to ...471, which is what Microsoft publishes. So every value in this batch is derived exactly with mpmath at 40 digits, THEN rounded to the double an engine actually holds, THEN formatted. String results are compared exactly, so a formatting-only difference (a trailing zero, "1i" for "i", a different digit count) fails the case and is recorded as its own divergence class, separate from a wrong numeric value. |
Matched |
| =IMSUB("1+i","1+i") | A number subtracted from itself, where both parts vanish | 0 | 0ProvenanceExact: (1+i) - (1+i) = 0 + 0i. Both parts are zero and the documented format collapses the result to a bare "0" rather than "0+0i". EXCEL'S COMPLEX-STRING FORMAT, which this corpus derives rather than assumes: a result is rendered as the real part, then the sign, then the imaginary coefficient followed by the suffix, with each part printed to at most 15 significant digits and trailing zeros stripped; a zero real part is omitted entirely, a zero imaginary part reduces the result to a bare real number, and an imaginary coefficient of exactly 1 or -1 prints as "i" / "-i" with no digit. That rule was written as a formatter in Python by batch D and validated against seven independently published Microsoft strings (IMCOS, IMCOSH, IMCOT, IMCSC, IMCSCH, IMEXP, IMLN); batch E re-ran that validation and then extended it, reproducing THIRTEEN MORE published Microsoft strings byte for byte (IMLOG10, IMLOG2, IMPOWER, both IMPRODUCT examples, IMSEC, IMSECH, IMSIN, IMSINH, IMSQRT, IMSUB, IMSUM, IMTAN) before predicting anything -- twenty published strings in all. ONE REFINEMENT BATCH E HAD TO MAKE: batch D fed the formatter the EXACT value computed at 40 digits, which happened to render identically to the IEEE double for all seven of its strings. That is not true here. A spreadsheet engine holds a double, not the exact value, and two of this batch's published strings only come out right if the derivation rounds to the nearest double BEFORE formatting: IMPOWER("2+3i",3) is exactly -46+9i in exact arithmetic but Microsoft publishes -46+9.00000000000001i, which is what exp(3*ln(2+3i)) gives in double precision; and IMSEC("4+3i") has an exact real part of -0.06529402785794704644..., whose 15-digit rounding ends ...47, while the correctly-rounded double -0.065294027857947051 rounds to ...471, which is what Microsoft publishes. So every value in this batch is derived exactly with mpmath at 40 digits, THEN rounded to the double an engine actually holds, THEN formatted. String results are compared exactly, so a formatting-only difference (a trailing zero, "1i" for "i", a different digit count) fails the case and is recorded as its own divergence class, separate from a wrong numeric value. |
Matched |
| =IMSUB("13+4j","5+3j") | The same documented subtraction written in the x+yj form the page also allows | 8+j | 8+jProvenanceThe page's description says "in x + yi or x + yj text format", so the j suffix is documented, not a guess. The arithmetic is identical to Microsoft's published example -- 8 and 1 -- and the answer must come back with the SAME suffix it was given, with the coefficient of 1 still printed as a bare "j". EXCEL'S COMPLEX-STRING FORMAT, which this corpus derives rather than assumes: a result is rendered as the real part, then the sign, then the imaginary coefficient followed by the suffix, with each part printed to at most 15 significant digits and trailing zeros stripped; a zero real part is omitted entirely, a zero imaginary part reduces the result to a bare real number, and an imaginary coefficient of exactly 1 or -1 prints as "i" / "-i" with no digit. That rule was written as a formatter in Python by batch D and validated against seven independently published Microsoft strings (IMCOS, IMCOSH, IMCOT, IMCSC, IMCSCH, IMEXP, IMLN); batch E re-ran that validation and then extended it, reproducing THIRTEEN MORE published Microsoft strings byte for byte (IMLOG10, IMLOG2, IMPOWER, both IMPRODUCT examples, IMSEC, IMSECH, IMSIN, IMSINH, IMSQRT, IMSUB, IMSUM, IMTAN) before predicting anything -- twenty published strings in all. ONE REFINEMENT BATCH E HAD TO MAKE: batch D fed the formatter the EXACT value computed at 40 digits, which happened to render identically to the IEEE double for all seven of its strings. That is not true here. A spreadsheet engine holds a double, not the exact value, and two of this batch's published strings only come out right if the derivation rounds to the nearest double BEFORE formatting: IMPOWER("2+3i",3) is exactly -46+9i in exact arithmetic but Microsoft publishes -46+9.00000000000001i, which is what exp(3*ln(2+3i)) gives in double precision; and IMSEC("4+3i") has an exact real part of -0.06529402785794704644..., whose 15-digit rounding ends ...47, while the correctly-rounded double -0.065294027857947051 rounds to ...471, which is what Microsoft publishes. So every value in this batch is derived exactly with mpmath at 40 digits, THEN rounded to the double an engine actually holds, THEN formatted. String results are compared exactly, so a formatting-only difference (a trailing zero, "1i" for "i", a different digit count) fails the case and is recorded as its own divergence class, separate from a wrong numeric value. |
Matched |
Google Sheets (executed 2026-08-31 via Drive import)
Google Sheets is a rolling service with no pinnable version, so this run is identified by its date. The corpus was imported to Drive as .xlsx, recalculated by Sheets, and exported back for readback.
| Formula | Description | Result | Expected | Verdict |
|---|---|---|---|---|
| =IMSUB("13+4i","5+3i") | Microsoft's documented worked example: the difference of two complex numbers | 8+i | 8+iProvenanceMicrosoft publishes '=IMSUB("13+4i","5+3i")' with the result 8+i. Derived from the identity the page renders as an image, (a+bi) - (c+di) = (a-c) + (b-d)i: 13-5 = 8 and 4-3 = 1. Exact integer arithmetic. The result is one of the two published Microsoft strings in which an imaginary coefficient of exactly 1 is printed as "i" with no digit -- the rule that the IMSQRT("-1") case in this same batch shows LibreOffice only got right from 25.2 onwards. EXCEL'S COMPLEX-STRING FORMAT, which this corpus derives rather than assumes: a result is rendered as the real part, then the sign, then the imaginary coefficient followed by the suffix, with each part printed to at most 15 significant digits and trailing zeros stripped; a zero real part is omitted entirely, a zero imaginary part reduces the result to a bare real number, and an imaginary coefficient of exactly 1 or -1 prints as "i" / "-i" with no digit. That rule was written as a formatter in Python by batch D and validated against seven independently published Microsoft strings (IMCOS, IMCOSH, IMCOT, IMCSC, IMCSCH, IMEXP, IMLN); batch E re-ran that validation and then extended it, reproducing THIRTEEN MORE published Microsoft strings byte for byte (IMLOG10, IMLOG2, IMPOWER, both IMPRODUCT examples, IMSEC, IMSECH, IMSIN, IMSINH, IMSQRT, IMSUB, IMSUM, IMTAN) before predicting anything -- twenty published strings in all. ONE REFINEMENT BATCH E HAD TO MAKE: batch D fed the formatter the EXACT value computed at 40 digits, which happened to render identically to the IEEE double for all seven of its strings. That is not true here. A spreadsheet engine holds a double, not the exact value, and two of this batch's published strings only come out right if the derivation rounds to the nearest double BEFORE formatting: IMPOWER("2+3i",3) is exactly -46+9i in exact arithmetic but Microsoft publishes -46+9.00000000000001i, which is what exp(3*ln(2+3i)) gives in double precision; and IMSEC("4+3i") has an exact real part of -0.06529402785794704644..., whose 15-digit rounding ends ...47, while the correctly-rounded double -0.065294027857947051 rounds to ...471, which is what Microsoft publishes. So every value in this batch is derived exactly with mpmath at 40 digits, THEN rounded to the double an engine actually holds, THEN formatted. String results are compared exactly, so a formatting-only difference (a trailing zero, "1i" for "i", a different digit count) fails the case and is recorded as its own divergence class, separate from a wrong numeric value. |
Matched |
| =IMSUB("1+i","1+i") | A number subtracted from itself, where both parts vanish | 0 | 0ProvenanceExact: (1+i) - (1+i) = 0 + 0i. Both parts are zero and the documented format collapses the result to a bare "0" rather than "0+0i". EXCEL'S COMPLEX-STRING FORMAT, which this corpus derives rather than assumes: a result is rendered as the real part, then the sign, then the imaginary coefficient followed by the suffix, with each part printed to at most 15 significant digits and trailing zeros stripped; a zero real part is omitted entirely, a zero imaginary part reduces the result to a bare real number, and an imaginary coefficient of exactly 1 or -1 prints as "i" / "-i" with no digit. That rule was written as a formatter in Python by batch D and validated against seven independently published Microsoft strings (IMCOS, IMCOSH, IMCOT, IMCSC, IMCSCH, IMEXP, IMLN); batch E re-ran that validation and then extended it, reproducing THIRTEEN MORE published Microsoft strings byte for byte (IMLOG10, IMLOG2, IMPOWER, both IMPRODUCT examples, IMSEC, IMSECH, IMSIN, IMSINH, IMSQRT, IMSUB, IMSUM, IMTAN) before predicting anything -- twenty published strings in all. ONE REFINEMENT BATCH E HAD TO MAKE: batch D fed the formatter the EXACT value computed at 40 digits, which happened to render identically to the IEEE double for all seven of its strings. That is not true here. A spreadsheet engine holds a double, not the exact value, and two of this batch's published strings only come out right if the derivation rounds to the nearest double BEFORE formatting: IMPOWER("2+3i",3) is exactly -46+9i in exact arithmetic but Microsoft publishes -46+9.00000000000001i, which is what exp(3*ln(2+3i)) gives in double precision; and IMSEC("4+3i") has an exact real part of -0.06529402785794704644..., whose 15-digit rounding ends ...47, while the correctly-rounded double -0.065294027857947051 rounds to ...471, which is what Microsoft publishes. So every value in this batch is derived exactly with mpmath at 40 digits, THEN rounded to the double an engine actually holds, THEN formatted. String results are compared exactly, so a formatting-only difference (a trailing zero, "1i" for "i", a different digit count) fails the case and is recorded as its own divergence class, separate from a wrong numeric value. |
Matched |
| =IMSUB("13+4j","5+3j") | The same documented subtraction written in the x+yj form the page also allows | 8+j | 8+jProvenanceThe page's description says "in x + yi or x + yj text format", so the j suffix is documented, not a guess. The arithmetic is identical to Microsoft's published example -- 8 and 1 -- and the answer must come back with the SAME suffix it was given, with the coefficient of 1 still printed as a bare "j". EXCEL'S COMPLEX-STRING FORMAT, which this corpus derives rather than assumes: a result is rendered as the real part, then the sign, then the imaginary coefficient followed by the suffix, with each part printed to at most 15 significant digits and trailing zeros stripped; a zero real part is omitted entirely, a zero imaginary part reduces the result to a bare real number, and an imaginary coefficient of exactly 1 or -1 prints as "i" / "-i" with no digit. That rule was written as a formatter in Python by batch D and validated against seven independently published Microsoft strings (IMCOS, IMCOSH, IMCOT, IMCSC, IMCSCH, IMEXP, IMLN); batch E re-ran that validation and then extended it, reproducing THIRTEEN MORE published Microsoft strings byte for byte (IMLOG10, IMLOG2, IMPOWER, both IMPRODUCT examples, IMSEC, IMSECH, IMSIN, IMSINH, IMSQRT, IMSUB, IMSUM, IMTAN) before predicting anything -- twenty published strings in all. ONE REFINEMENT BATCH E HAD TO MAKE: batch D fed the formatter the EXACT value computed at 40 digits, which happened to render identically to the IEEE double for all seven of its strings. That is not true here. A spreadsheet engine holds a double, not the exact value, and two of this batch's published strings only come out right if the derivation rounds to the nearest double BEFORE formatting: IMPOWER("2+3i",3) is exactly -46+9i in exact arithmetic but Microsoft publishes -46+9.00000000000001i, which is what exp(3*ln(2+3i)) gives in double precision; and IMSEC("4+3i") has an exact real part of -0.06529402785794704644..., whose 15-digit rounding ends ...47, while the correctly-rounded double -0.065294027857947051 rounds to ...471, which is what Microsoft publishes. So every value in this batch is derived exactly with mpmath at 40 digits, THEN rounded to the double an engine actually holds, THEN formatted. String results are compared exactly, so a formatting-only difference (a trailing zero, "1i" for "i", a different digit count) fails the case and is recorded as its own divergence class, separate from a wrong numeric value. |
Matched |
LibreOffice Calc 25.8.7.3 (tested 2026-08-31)
| Formula | Description | Result | Expected | Verdict |
|---|---|---|---|---|
| =IMSUB("13+4i","5+3i") | Microsoft's documented worked example: the difference of two complex numbers | 8+i | 8+iProvenanceMicrosoft publishes '=IMSUB("13+4i","5+3i")' with the result 8+i. Derived from the identity the page renders as an image, (a+bi) - (c+di) = (a-c) + (b-d)i: 13-5 = 8 and 4-3 = 1. Exact integer arithmetic. The result is one of the two published Microsoft strings in which an imaginary coefficient of exactly 1 is printed as "i" with no digit -- the rule that the IMSQRT("-1") case in this same batch shows LibreOffice only got right from 25.2 onwards. EXCEL'S COMPLEX-STRING FORMAT, which this corpus derives rather than assumes: a result is rendered as the real part, then the sign, then the imaginary coefficient followed by the suffix, with each part printed to at most 15 significant digits and trailing zeros stripped; a zero real part is omitted entirely, a zero imaginary part reduces the result to a bare real number, and an imaginary coefficient of exactly 1 or -1 prints as "i" / "-i" with no digit. That rule was written as a formatter in Python by batch D and validated against seven independently published Microsoft strings (IMCOS, IMCOSH, IMCOT, IMCSC, IMCSCH, IMEXP, IMLN); batch E re-ran that validation and then extended it, reproducing THIRTEEN MORE published Microsoft strings byte for byte (IMLOG10, IMLOG2, IMPOWER, both IMPRODUCT examples, IMSEC, IMSECH, IMSIN, IMSINH, IMSQRT, IMSUB, IMSUM, IMTAN) before predicting anything -- twenty published strings in all. ONE REFINEMENT BATCH E HAD TO MAKE: batch D fed the formatter the EXACT value computed at 40 digits, which happened to render identically to the IEEE double for all seven of its strings. That is not true here. A spreadsheet engine holds a double, not the exact value, and two of this batch's published strings only come out right if the derivation rounds to the nearest double BEFORE formatting: IMPOWER("2+3i",3) is exactly -46+9i in exact arithmetic but Microsoft publishes -46+9.00000000000001i, which is what exp(3*ln(2+3i)) gives in double precision; and IMSEC("4+3i") has an exact real part of -0.06529402785794704644..., whose 15-digit rounding ends ...47, while the correctly-rounded double -0.065294027857947051 rounds to ...471, which is what Microsoft publishes. So every value in this batch is derived exactly with mpmath at 40 digits, THEN rounded to the double an engine actually holds, THEN formatted. String results are compared exactly, so a formatting-only difference (a trailing zero, "1i" for "i", a different digit count) fails the case and is recorded as its own divergence class, separate from a wrong numeric value. |
Matched |
| =IMSUB("1+i","1+i") | A number subtracted from itself, where both parts vanish | 0 | 0ProvenanceExact: (1+i) - (1+i) = 0 + 0i. Both parts are zero and the documented format collapses the result to a bare "0" rather than "0+0i". EXCEL'S COMPLEX-STRING FORMAT, which this corpus derives rather than assumes: a result is rendered as the real part, then the sign, then the imaginary coefficient followed by the suffix, with each part printed to at most 15 significant digits and trailing zeros stripped; a zero real part is omitted entirely, a zero imaginary part reduces the result to a bare real number, and an imaginary coefficient of exactly 1 or -1 prints as "i" / "-i" with no digit. That rule was written as a formatter in Python by batch D and validated against seven independently published Microsoft strings (IMCOS, IMCOSH, IMCOT, IMCSC, IMCSCH, IMEXP, IMLN); batch E re-ran that validation and then extended it, reproducing THIRTEEN MORE published Microsoft strings byte for byte (IMLOG10, IMLOG2, IMPOWER, both IMPRODUCT examples, IMSEC, IMSECH, IMSIN, IMSINH, IMSQRT, IMSUB, IMSUM, IMTAN) before predicting anything -- twenty published strings in all. ONE REFINEMENT BATCH E HAD TO MAKE: batch D fed the formatter the EXACT value computed at 40 digits, which happened to render identically to the IEEE double for all seven of its strings. That is not true here. A spreadsheet engine holds a double, not the exact value, and two of this batch's published strings only come out right if the derivation rounds to the nearest double BEFORE formatting: IMPOWER("2+3i",3) is exactly -46+9i in exact arithmetic but Microsoft publishes -46+9.00000000000001i, which is what exp(3*ln(2+3i)) gives in double precision; and IMSEC("4+3i") has an exact real part of -0.06529402785794704644..., whose 15-digit rounding ends ...47, while the correctly-rounded double -0.065294027857947051 rounds to ...471, which is what Microsoft publishes. So every value in this batch is derived exactly with mpmath at 40 digits, THEN rounded to the double an engine actually holds, THEN formatted. String results are compared exactly, so a formatting-only difference (a trailing zero, "1i" for "i", a different digit count) fails the case and is recorded as its own divergence class, separate from a wrong numeric value. |
Matched |
| =IMSUB("13+4j","5+3j") | The same documented subtraction written in the x+yj form the page also allows | 8+j | 8+jProvenanceThe page's description says "in x + yi or x + yj text format", so the j suffix is documented, not a guess. The arithmetic is identical to Microsoft's published example -- 8 and 1 -- and the answer must come back with the SAME suffix it was given, with the coefficient of 1 still printed as a bare "j". EXCEL'S COMPLEX-STRING FORMAT, which this corpus derives rather than assumes: a result is rendered as the real part, then the sign, then the imaginary coefficient followed by the suffix, with each part printed to at most 15 significant digits and trailing zeros stripped; a zero real part is omitted entirely, a zero imaginary part reduces the result to a bare real number, and an imaginary coefficient of exactly 1 or -1 prints as "i" / "-i" with no digit. That rule was written as a formatter in Python by batch D and validated against seven independently published Microsoft strings (IMCOS, IMCOSH, IMCOT, IMCSC, IMCSCH, IMEXP, IMLN); batch E re-ran that validation and then extended it, reproducing THIRTEEN MORE published Microsoft strings byte for byte (IMLOG10, IMLOG2, IMPOWER, both IMPRODUCT examples, IMSEC, IMSECH, IMSIN, IMSINH, IMSQRT, IMSUB, IMSUM, IMTAN) before predicting anything -- twenty published strings in all. ONE REFINEMENT BATCH E HAD TO MAKE: batch D fed the formatter the EXACT value computed at 40 digits, which happened to render identically to the IEEE double for all seven of its strings. That is not true here. A spreadsheet engine holds a double, not the exact value, and two of this batch's published strings only come out right if the derivation rounds to the nearest double BEFORE formatting: IMPOWER("2+3i",3) is exactly -46+9i in exact arithmetic but Microsoft publishes -46+9.00000000000001i, which is what exp(3*ln(2+3i)) gives in double precision; and IMSEC("4+3i") has an exact real part of -0.06529402785794704644..., whose 15-digit rounding ends ...47, while the correctly-rounded double -0.065294027857947051 rounds to ...471, which is what Microsoft publishes. So every value in this batch is derived exactly with mpmath at 40 digits, THEN rounded to the double an engine actually holds, THEN formatted. String results are compared exactly, so a formatting-only difference (a trailing zero, "1i" for "i", a different digit count) fails the case and is recorded as its own divergence class, separate from a wrong numeric value. |
Matched |
Docs & syntax
- Excel (desktop): official documentation
- Google Sheets: official documentation
- LibreOffice Calc: official documentation