Loan amortization schedule in Google Sheets
Split each payment into interest and principal and track the remaining balance.
Written by PhilisPublished June 9, 2026Last updated July 25, 202611 min
Use PMT for the fixed payment, calculate interest from the opening balance and periodic rate, then subtract principal from the balance each period.
Before you build a loan payment schedule, set up a clean source range and one result you can check by hand. That gives you a known answer before the sheet grows.
This article shows how to build a loan payment schedule. The sample sheet uses ordinary rows so you can copy the method into an existing file without rebuilding everything.
Loan amortization schedule in Google Sheets
- 01Make a safe copy
Duplicate the source tab or file before changing formulas, ranges or formatting.
- 02Set up the source rows
Add the fields needed to build a loan payment schedule. Keep one record on each row and one field in each column.
- 03Add the method
Enter =-PMT($B$2/12,$B$3,$B$1) in a test cell and check its first result.
- 04Check a known case
Pick one row whose answer you already know and compare it with the sheet result.
- 05Test the awkward rows
Check blanks, zeros, repeated entries and one row that should not match.
- 06Apply it to the full range
Copy the formula or rule only after the sample cases return the expected result.
Set up the sheet for Loan amortization schedule
Keep the source table rectangular. A single header row, no merged cells and consistent cell types make the work much easier to check.
Place settings, fixed rates or allowed labels on a separate tab. Name them clearly so another person can read the file without tracing every cell.
- Match annual and monthly units
- Check payment sign conventions
- Keep rate and term in fixed cells
- Compare the final balance with zero
Check the first result before copying it
A result that looks plausible can still be wrong. Work through one row manually, compare it with the Sheet and check every referenced cell.
Next, test a blank row and an unusual row. These two checks catch many range, type and copied-reference mistakes before they spread.
=-PMT($B$2/12,$B$3,$B$1)Keep the file reliable as new rows arrive
Leave input columns visually separate from calculated columns. Protect formulas when several people edit the same file, and keep dropdown lists or settings outside the main table.
Add a short check near the result: row count, unmatched count, last refresh time or a manual spot check. The right check depends on the job, but it should make a bad update easy to notice.
Questions people ask
What formula calculates a loan payment?＋
PMT calculates the regular payment from the periodic rate, number of periods and principal.
Why is PMT negative?＋
Spreadsheet finance functions use cash-flow signs. Prefix PMT with a minus sign if you want a positive payment display.
Can I add extra payments?＋
Yes. Add an extra-principal column and subtract it from the closing balance.
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