How to convert an annual growth rate to monthly
✓ Verified in LibreOffice 25.8.7.3 ✓ Verified in Google Sheets (2026-08-30)De-compound a yearly rate into its monthly equivalent — forecasts, run-rate models.
The formula
| App | Formula | Notes |
|---|---|---|
| Excel (desktop) | =(1+A2)^(1/12)-1 | A2 = annual rate. The 12th root, not division by 12 — compounding isn't linear. |
| Google Sheets | =(1+A2)^(1/12)-1 | Identical. |
| LibreOffice Calc | =(1+A2)^(1/12)-1 | Identical. |
How it works
Twelve months of growth multiply, so the monthly rate is the 12th ROOT of (1 + annual) minus one: a 12.68% year unwinds to exactly 1% per month — while naive division (12.68/12 = 1.057%) overshoots, compounding to 13.4% when reapplied. The same formula generalizes: any period conversion is (1+rate)^(periods_ratio)−1 — quarterly from annual uses 1/4, annual from daily uses 365. It's CAGR's little sibling.
Verified, not just documented
We ran =ROUND((1+A2)^(1/12)-1,4) in LibreOffice 25.8.7.3 (headless, with forced recalculation) and it returned 0.01 — 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 0.01 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.