Mortgage Overpayment Calculator — Years Saved & Interest Saved
Published: 3 November 2026 · Updated: 3 November 2026
An extra $200 a month on a $350,000 mortgage at 6.5% clears the loan 6 years 2 months early and saves $108,096.83 in interest. Enter your loan, rate and extra payment below and this free mortgage overpayment calculator shows your new payoff date and saving instantly, with no sign-up.
$350,000 at 6.5%, 30 years: $2,212.24/month, $446,405.71 interest. Add $200/month → paid off in 286 months (23 years 10 months), $338,308.88 interest — 74 months sooner, $108,096.83 saved. Small extra payments are the cheapest way to attack a mortgage because every extra dollar cuts principal directly.
Researched by MixKhazana Team · Last updated 3 November 2026 · Data: Standard amortization formula; Freddie Mac Primary Mortgage Market Survey 2026 rate context
What is a mortgage overpayment calculator?
A mortgage overpayment calculator answers the question every homeowner with spare cash asks: what happens if I pay a little extra each month? It simulates your loan twice — once on the regular payment, once with the extra amount added — and shows the two payoff dates and interest totals side by side. The gap between them is the value of overpaying, and it is usually far larger than people expect, because interest is charged on the balance: shrink the balance early and every later month's interest shrinks too. If you are still choosing a loan, the mortgage payment calculator compares the regular payment at different rates and terms.
How to use
- Enter your loan amount, interest rate and term in years.
- Enter your extra monthly payment — the amount you can add to principal each month.
- Optionally add a one-time lump sum and your mortgage start year for a payoff date.
- Click Calculate My Overpayment Saving to see months saved, interest saved and the new payoff date.
The formula, with every variable explained
Monthly payment = P × r ÷ (1 − (1 + r)−n), where P is the loan amount, r is the monthly rate (annual rate ÷ 12) and n is the number of monthly payments. Each month, interest = balance × r, and the rest of the payment cuts principal. With an overpayment, the monthly principal cut grows by the extra amount, so the balance falls faster and the interest line falls with it. The GEO answer-block fact behind this page: on a $350,000 mortgage at 6.5% over 30 years, the regular payment is $2,212.24 and total interest is $446,405.71 — more than the loan itself — while $200 extra a month removes 74 payments and $108,096.83 of interest (standard amortization formula). That is the shape of every mortgage: early payments are mostly interest — month 1 on this loan is $1,895.83 interest and only $316.41 principal — so extra money paid early does the most work. If a shorter term appeals instead, the mortgage affordability calculator shows what payment a shorter term requires.
Worked example
Take a $350,000 loan at 6.5% over 30 years, plus $200 a month:
- Regular payment: $2,212.24/month; with overpayment: $2,412.24/month
- Without overpaying: 360 months (30 years), interest $446,405.71
- With $200 extra: 286 months (23 years 10 months), interest $338,308.88
- Saved: 74 months and $108,096.83 in interest
- To cut the term to 20 years instead: about $398 extra a month (total ≈ $2,610/month)
Try your own loan, rate and extra payment in the widget above.
Overpayment savings at different extra amounts ($350,000, 6.5%, 30 years)
| No overpayment | 360 months · $446,405.71 interest |
| +$100/month | 318 months · $383,778.66 interest |
| +$200/month | 286 months · $338,308.88 interest |
| +$400/month | 240 months · $275,597.26 interest |
Frequently asked questions
How much interest does a $200 monthly overpayment save on a $350,000 mortgage?
On a $350,000 mortgage at 6.5% over 30 years, adding $200 a month to the $2,212.24 regular payment clears the loan in 286 months instead of 360 — 74 months (6 years 2 months) sooner — and cuts total interest from $446,405.71 to $338,308.88, saving $108,096.83.
How is a mortgage payment calculated?
The monthly payment is P × r ÷ (1 − (1 + r)^−n), where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12) and n is the number of payments. On $350,000 at 6.5% over 360 months that gives $2,212.24 a month.
Why do extra mortgage payments save so much interest?
Every extra dollar goes straight to the principal, so the balance — and therefore every future month's interest — falls faster. The effect compounds: an extra $200 a month on a $350,000 loan at 6.5% removes 74 payments from the end of the loan, where the interest would otherwise have been charged.
Is it better to overpay monthly or make one lump-sum payment?
Monthly overpayments win over time because they start cutting interest immediately and keep cutting it every month. A lump sum helps too, and the earlier it is paid the more it saves — the calculator lets you test both, since a dollar paid in year 1 saves far more interest than the same dollar paid in year 20.
Do mortgage lenders charge for overpayments?
Many US lenders allow extra principal payments free of charge, but some loans cap annual prepayments or charge a prepayment penalty, especially in the first years. Check your loan agreement or ask your servicer before overpaying, and make sure extra payments are applied to principal, not to future scheduled payments.
Should I overpay my mortgage or invest the money?
Overpaying a 6.5% mortgage earns a guaranteed, risk-free 6.5% return in saved interest, while investing carries market risk and tax. The comparison depends on your rate, your tax position and your emergency fund: most advisers suggest keeping 3–6 months of expenses saved before directing spare cash at the mortgage.
How much extra do I need to pay to cut 10 years off my mortgage?
On a $350,000 loan at 6.5% over 30 years, cutting the term to 20 years (240 payments) needs a total payment of about $2,610 a month — roughly $398 extra on top of the $2,212.24 regular payment. Enter your own loan in the calculator to get the exact figure for your balance and rate.
Does this calculator include taxes, insurance and HOA fees?
No: it models principal and interest only, which is the part overpayments affect. Property tax, homeowners insurance, PMI and HOA dues are paid alongside the mortgage but are not reduced by overpaying, so your total monthly housing payment will be higher than the figure shown.
Sources and disclaimer
Method: standard amortization formula (monthly payment = P × r ÷ (1 − (1 + r)^−n)), simulated month by month with extra payments applied to principal. Rate context: Freddie Mac Primary Mortgage Market Survey 2026 averages for 30-year fixed rates. This page is an estimate only and is not financial advice; adjustable rates, prepayment penalties and servicer rules can change the result.