See how much time and interest you save by paying extra principal on your mortgage every month. The calculator runs your loan with and without the added amount and shows the months and dollars saved.
This is an estimate based on your current payment and rate remaining constant. Confirm your loan doesn’t have prepayment penalties before adding extra payments.
How Much Does Paying Extra Principal Every Month Save?
More than most people expect. On a $300,000, 30-year loan at 6.5%, the payment is about $1,896. Adding $200 a month pays it off in about 276 months instead of 360, roughly 7 years early, and saves about $103,450 in interest. That’s what happens if you pay an extra $200 a month on a 30 year mortgage at that rate.
| Extra per month | Paid off in | Time saved | Interest saved |
|---|---|---|---|
| $100 | ~311 months | ~4 years | ~$61,000 |
| $200 | ~276 months | ~7 years | ~$103,450 |
| $500 | ~210 months | ~12.5 years | ~$179,760 |
| $717 | 180 months | 15 years | ~$212,200 |
So if you pay an extra 100 a month on this mortgage you save around four years, an extra $500 a month saves about $179,760, and the last row shows how much extra it takes to pay off a 30 year mortgage in 15 years.
How the Calculator Works
It works out how many months your balance takes to reach zero at your current payment, then again with the extra added, and compares the two. Extra money goes straight to principal, which shortens the loan and cuts total interest.
Formula: Remaining Months = −ln(1 − r×Balance÷Payment) ÷ ln(1+r), where r = Interest Rate ÷ 12 ÷ 100 — calculated once using the current payment, and again using (Current Payment + Extra), then compared
- Balance: the remaining loan balance today
- Rate: the loan’s current annual interest rate
- Payment: the current scheduled monthly payment
- Extra: the additional amount added to each monthly payment
Example Scenarios
| Balance | Rate | Payment | Extra | Time Saved | Interest Saved |
|---|---|---|---|---|---|
| $280,000 | 6.5% | $1,900 | $200 | ~59 months | ~$65,000 |
| $150,000 | 5.0% | $1,200 | $100 | ~19 months | ~$7,400 |
| $400,000 | 7.0% | $2,800 | $400 | ~84 months | ~$144,000 |
| $100,000 | 4.5% | $900 | $150 | ~26 months | ~$5,700 |
Checks Before You Pay Extra
The numbers above are the savings in theory; a few checks make sure they happen.
- Tell your lender the extra money goes to principal. Some servicers apply unlabelled extra funds to the next scheduled payment instead.
- Check your loan agreement for prepayment penalties before paying ahead.
- Use the current balance and rate from your latest statement, not the original loan amount.
Paying ahead is not always the best use of spare cash. An emergency fund, high-interest debt or employer retirement matching may come first, and no extra mortgage payment calculator can weigh those trade-offs for you. Rules and tax treatment vary by country, so this is general information. The amortizing loan article on Wikipedia explains why early extra payments save the most.
Common questions about extra mortgage payments
What happens if I pay an extra $200 a month on my 30 year mortgage?
On a $300,000 loan at 6.5%, the regular payment is about $1,896. Adding $200 pays it off in about 276 months instead of 360, roughly 7 years sooner, and saves about $103,450 in interest.How much does an extra $500 a month save on a mortgage?
On the same $300,000 loan at 6.5%, $500 extra a month cuts about 150 months, or 12.5 years, and saves roughly $179,760 in interest. Your own figures depend on your balance and rate.How much extra do I need to pay off a 30 year mortgage in 15 years?
For $300,000 at 6.5%, the 15-year payment is about $2,613 against $1,896 for 30 years, so you’d add about $717 a month. Enter your own balance and rate and adjust the extra amount until the payoff time reads 180 months.Why does a small extra payment save so much interest?
Extra payments cut principal straight away, and every dollar removed early stops accruing interest for the rest of the term. The earlier you start, the more it saves.Should I confirm anything with my lender before paying extra?
Yes. Make sure extra money goes to principal rather than a future scheduled payment, and that the loan has no prepayment penalty, since either can reduce the benefit.Does this calculator assume the interest rate stays the same?
Yes. It assumes your current rate and payment stay constant, which fits a fixed-rate mortgage. An adjustable-rate loan needs recalculating whenever the rate resets.Related Calculators
Before deciding how much extra to add, it can help to recheck your full monthly payment breakdown or see your existing amortization schedule in detail.