How to sum values by day of the week
✓ Verified in LibreOffice 25.8.7.3 ✓ Verified in Google Sheets (2026-08-30)Total all the Mondays (or any weekday) in dated data — traffic by weekday, weekend vs weekday sales.
The formula
| App | Formula | Notes |
|---|---|---|
| Excel (desktop) | =SUMPRODUCT((WEEKDAY(A2:A100,2)=1)*B2:B100) | Mode 2: Monday=1..Sunday=7. Change the =1 for other days; >5 for weekends. |
| Google Sheets | =SUMPRODUCT((WEEKDAY(A2:A100,2)=1)*B2:B100) | Identical. |
| LibreOffice Calc | =SUMPRODUCT((WEEKDAY(A2:A100,2)=1)*B2:B100) | Identical. |
How it works
WEEKDAY runs over the whole date column (as an array), the =1 test keeps Mondays, and SUMPRODUCT totals the matching amounts: the two Mondays here (serials 46223 = July 20 and 46230 = July 27, 2026) carry 100 + 25 = 125, while Tuesday's 50 is excluded. There's no SUMIF criterion that can see weekdays directly — this computed-condition pattern (or a helper column of WEEKDAY values feeding SUMIF) is the standard route.
Verified, not just documented
We ran =SUMPRODUCT((WEEKDAY(A2:A4,2)=1)*B2:B4) in LibreOffice 25.8.7.3 (headless, with forced recalculation) and it returned 125 — exactly the expected result. We then ran the same formulas in Google Sheets, executed 2026-08-30: a formula-only workbook goes into Google Drive, which converts it to a Sheet and recalculates every formula with Google’s own engine, and comes back out as .xlsx carrying the values Google computed. It returned 125 for the worked example, the same value LibreOffice produced. Both engines’ numbers on this page are executed results. The Excel formula follows Microsoft’s official documented syntax — we do not run desktop Excel.
Functions used
SUMPRODUCT · WEEKDAY — see full Excel, Google Sheets & LibreOffice compatibility for each.
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