Why extra principal is so effective early
Interest each month is charged on the outstanding balance. Reduce the balance today and you eliminate the interest that balance would have generated for every remaining month of the loan.
On a $350,000 loan at 6.5% over 30 years, adding $200 a month from the start cuts roughly five years off the term and saves in the region of $95,000 in interest. The same $200 added in year 20 saves a small fraction of that, because there is far less remaining interest left to prevent. Timing dominates: the earliest extra payments are worth several times the last ones.
Enter an extra monthly amount in the calculator above and open the repayment summary to see the revised payoff date and interest saved for your own loan.
Methods that work
- A fixed extra amount each month: the simplest and easiest to automate. Even $50 or $100 changes the payoff date measurably over a 30-year loan.
- Biweekly payments: paying half your monthly amount every two weeks produces 26 half-payments, or 13 full payments, a year. The extra annual payment typically removes four to six years from a 30-year term. Achieve the same result without a servicer programme by dividing your payment by 12 and adding that to each month.
- Annual lump sums: directing a bonus or tax refund to principal once a year is less consistent but still effective, particularly in the first decade.
- Rounding up: paying $2,400 against a $2,212 required payment is easy to sustain and requires no separate decision each month.
Make sure the money reaches principal
This is the step that most often goes wrong. Servicers do not universally apply extra money to principal by default. Some hold it as an unapplied balance until it accumulates to a full payment, some credit it toward next month's payment, and a payment applied in advance saves you nothing.
Specify "apply to principal" when making the payment, use the dedicated principal-only field if your servicer's portal has one, and check the next statement to confirm the balance dropped by the extra amount. Verify it again after any servicing transfer, since your loan may be sold and the new servicer's default handling can differ.
Also confirm your loan carries no prepayment penalty. These are uncommon on modern conforming loans and prohibited on VA loans, but they do exist, particularly on non-qualified mortgages.
Recasting: the option most borrowers have not heard of
If you make a large lump-sum principal payment, ask your servicer about a recast. Recasting re-amortizes the remaining balance over the remaining term, which lowers your required monthly payment while keeping your existing interest rate and payoff date intact. It usually costs a few hundred dollars in fees.
This is different from a refinance: there is no new loan, no credit check, no appraisal and no closing costs, and you keep your original rate. That makes recasting especially valuable when current market rates are above the rate you hold. It is a common tool after selling a previous home and applying the proceeds to a new mortgage. Not every loan type is eligible, so ask before making the lump-sum payment.
When paying extra is the wrong priority
A prepayment earns you a guaranteed return equal to your mortgage rate, which is good but not always the best available use of a dollar. Work through this order first:
- Build a basic emergency fund. Money paid into a mortgage is difficult to retrieve; you cannot withdraw it when the car fails. Home equity is illiquid without a sale or a new loan.
- Capture any employer retirement match in full. A 50% or 100% match is an immediate return no mortgage rate can approach.
- Clear higher-interest debt. Credit cards and most personal loans cost far more than a mortgage, so paying them first is straightforwardly better arithmetic.
- If you carry mortgage insurance on a conventional loan, note that prepaying toward the 80% loan-to-value threshold lets you request PMI cancellation, which adds an extra return on top of the interest saved.
Prepaying versus investing
Once the priorities above are handled, the choice between prepaying and investing comes down to your mortgage rate against expected after-tax investment returns, adjusted for risk. Prepayment is a guaranteed, risk-free return; equity market returns are neither guaranteed nor smooth.
With a mortgage rate around 3%, the historical case for investing instead is strong. Nearer 7% and above, prepayment becomes competitive with risky assets on a risk-adjusted basis, and it is certain. There is also a behavioural argument that deserves weight: an automatic extra principal payment happens whether or not you feel disciplined that month, and a paid-off house materially reduces the income you need in retirement.
Frequently asked questions
How much can I save by paying extra on my mortgage?
It depends on the amount and, critically, on how early you start. On a $350,000 loan at 6.5%, an extra $200 a month from the beginning saves roughly $95,000 in interest and retires the loan about five years early. Use the extra payment field in the calculator for your own figures.
Do biweekly mortgage payments really work?
Yes, though the mechanism is unglamorous. Twenty-six half-payments equal thirteen monthly payments a year, and that one extra payment typically removes four to six years from a 30-year term. You can replicate it for free by adding one twelfth of your payment each month rather than paying a servicer's biweekly programme fee.
Will my monthly payment go down if I pay extra?
No. Extra principal shortens the loan but leaves the required payment unchanged. To lower the required payment after a large lump sum, ask your servicer about recasting, which re-amortizes the balance while keeping your rate.
What is mortgage recasting?
Recasting re-amortizes your remaining balance over the remaining term after a large principal payment, reducing the required monthly payment. It keeps your existing interest rate and costs a small fee, with no new loan, credit check or appraisal.
Should I pay off my mortgage early or invest?
Fund an emergency reserve, capture any employer retirement match and clear high-interest debt first. Beyond that, compare your mortgage rate to realistic after-tax investment returns. Prepayment is a guaranteed return; investing offers a higher expected return with real risk.
Related calculators
How this estimate is built
Principal and interest come from the standard amortization formula, worked through in full on the formula reference page. Property tax, insurance, PMI and loan-program figures layer on top from published assumptions — each one sourced, dated and listed on the methodology page. Every result here is an estimate built from public data, not a quote: confirm the specifics with a lender before relying on it.
For developers
This calculation is also available as a REST API and through an MCP server, both running the same engine as this page — so the figures match by construction rather than by convention. No key required.