# How many months do extra payments save on a loan in Excel

Compare NPER with and without the extra amount: `=NPER(B3/12,-B4,B2)-NPER(B3/12,-(B4+B5),B2)`.

**Excel:** `=NPER(B3/12,-B4,B2)-NPER(B3/12,-(B4+B5),B2)` (Every current version)

**Google Sheets:** the same formula works.

## Example

Sample data (row 1 is the header):

| A | B |
| --- | --- |
| Mortgage | Value |
| Balance | 240000 |
| Annual interest rate | 0.0575 |
| Monthly payment | 1650 |
| Extra each month | 200 |
| Months saved |  |

Formula in B6: `=NPER(B3/12,-B4,B2)-NPER(B3/12,-(B4+B5),B2)`

Result: 46.5

## How it works

NPER returns how many payments clear the balance at a given payment. The first NPER uses the normal payment, the second the payment plus the extra $200, and the difference is the time saved: about 46 months, almost four years. Extra money goes straight to principal, so less interest builds up every month after.

## Other ways

- `=(NPER(B3/12,-B4,B2)*B4)-(NPER(B3/12,-(B4+B5),B2)*(B4+B5))`: The interest saved: total paid without the extra minus total paid with it. (Interest saved: about $36,000.)
- `=NPER(B3/12,-(B4+B5),B2)`: The new payoff time on its own. (About 203 months with the extra payment.)

## Common mistakes

- NPER returns #NUM! if a payment doesn't cover the monthly interest, $1,150 here.
- This assumes the extra is paid every month from now on. A one-off lump sum is better modeled by reducing the balance.

## Questions

**How do I see the result in years?**

Divide by 12: `=B6/12`.

**What about a lump sum instead?**

Reduce the balance: `=NPER(B3/12,-B4,B2)-NPER(B3/12,-B4,B2-10000)` for a $10,000 payment now.

Every formula and result on this page was checked by running it in the Spreadsheet Practice formula engine on 2026-10-30.

Source: https://spreadsheetpractice.com/formulas/months-saved-by-extra-payments