How to calculate the monthly savings needed for a goal
✓ Verified in LibreOffice 25.8.7.3Working backward from a target: what to put away each month to hit $X by a date.
The formula
| App | Formula | Notes |
|---|---|---|
| Excel | =-PMT(A2/12,B2*12,0,C2) | A2=annual return, B2=years, C2=target. The 0 = starting from nothing; put current savings there instead if you have a head start. |
| Google Sheets | =-PMT(A2/12,B2*12,0,C2) | Identical. |
| LibreOffice Calc | =-PMT(A2/12,B2*12,0,C2) | Identical. |
How it works
PMT solves for the payment in any annuity — pointing its future-value argument at your target makes it answer the savings question: $20,000 in 5 years at 4% needs $301.66/month, noticeably less than the naive 20,000÷60 = $333 because growth does part of the work. At 0% return the two agree exactly. The minus sign flips PMT's pay-out convention into a positive deposit; a nonzero present-value argument accounts for money already saved.
Verified, not just documented
We ran =ROUND(-PMT(A2/12,B2*12,0,C2),2) in LibreOffice 25.8.7.3 (headless, with forced recalculation) and it returned 301.66 — exactly the expected result. Every formula here is confirmed by actually executing it.