Paying off your mortgage early: extra payments, biweekly plans and the actual math
Every dollar sent to principal ahead of schedule erases the interest that dollar would have carried for the rest of the loan. That is the entire mechanism. What follows from it is less obvious: which method is worth the trouble, why your payment does not drop, and why a paid service to do it for you is almost never worth the fee.
The four levers
- Extra principal every month. A fixed amount added to the regular payment, marked for principal.
- A thirteenth payment a year. One extra full payment, or one-twelfth of the payment added monthly, which is the same thing spread out.
- A lump sum. A bonus, a tax refund, the proceeds of a sale.
- Rounding up. Paying $2,600 instead of $2,528 — the version people actually stick to.
What each does to a $400,000 loan
Take a $400,000 balance at an illustrative 6.5% over 30 years: about $2,528 a month in principal and interest, and roughly $510,000 of interest if you never send a dollar extra.
| What you do | Loan paid off in | Total interest | Interest saved |
|---|---|---|---|
| Nothing | 30 years | ≈ $510,000 | — |
| +$100 a month | ≈ 26 years 10 months | ≈ $446,000 | ≈ $64,000 |
| +$200 a month | ≈ 24 years 5 months | ≈ $398,000 | ≈ $112,000 |
| One extra payment a year (≈ +$211/mo) | ≈ 24 years 2 months | ≈ $394,000 | ≈ $116,000 |
| +$500 a month | ≈ 19 years 5 months | ≈ $305,000 | ≈ $205,000 |
| $10,000 lump sum at the end of year 1 | ≈ 28 years | ≈ $459,000 | ≈ $51,000 |
Illustrative arithmetic on a standard amortization schedule, not an offer, and it ignores taxes, insurance and any fee your servicer charges. Two readings matter. Early dollars do far more work than late ones — $10,000 sent in year one outperforms the same $10,000 sent in year fifteen by a wide margin. And the curve flattens: the first $100 a month buys about three years, the jump from $200 to $500 buys five more. Payment math for other balances and rates is on our payment tables.
Biweekly plans: the version that works and the version that does not
A biweekly plan splits your monthly payment in half and collects it every two weeks. Because there are 52 weeks in a year, that is 26 half payments — 13 full payments instead of 12. The extra payment is the entire benefit. There is no magic in the fortnightly rhythm itself.
Whether it works depends on what the servicer does with each half. If the half payments are held in a suspense account until a full payment accumulates, and the thirteenth is then applied to principal, you get the result in the table above. If they are simply held and applied on the normal due date, you get nothing but a different calendar.
The version to avoid is the third-party program that charges a setup fee plus a fee per transaction to do this on your behalf. The CFPB is blunt about it: you can usually reach the same result yourself for free by adding one-twelfth of your payment each month, and it has taken enforcement action against a biweekly administrator over how the savings were marketed, noting that some consumers paid more in fees than they saved. Before enrolling in anything, ask your own servicer two questions: do you accept biweekly drafts, and do you charge for them?
Making sure the money actually hits principal
- Use the "additional principal" field in the servicer portal, not a larger single payment amount. Money sent without instruction is often applied to the next scheduled installment, or parked in suspense — which does nothing for you.
- Send it as a separate transaction if the portal has no such field, with "apply to principal" written on the memo line or in the online note.
- Check the next statement. The principal balance should have dropped by your regular principal portion plus the extra. If the statement instead shows a payment made ahead for next month, call and ask for it to be reapplied.
- Do not skip a payment because you are ahead. Paying extra rarely changes the fact that the next monthly payment is still due on its date.
- Keep escrow separate. Extra principal does not reduce the taxes and insurance portion of your payment, as our guide to escrow accounts explains.
Prepayment penalties and other fine print
On most modern residential loans, prepaying is free. Regulation Z sharply restricts prepayment penalties on closed-end mortgages: where one is permitted at all, it is confined to the early years of the loan and capped on a declining scale, and it cannot be attached to an adjustable-rate or higher-priced loan. Conforming conventional loans sold to Fannie Mae or Freddie Mac generally carry none. Read your note anyway, and if the loan is a portfolio, non-QM or business-purpose loan — including most hard money loans, where prepayment terms and interest guarantees are normal — check the prepayment clause before you send anything.
When prepaying is the wrong call
- No emergency fund. Money in the house is not spendable. A home equity line can be reduced or frozen; a savings account cannot.
- Higher-rate debt exists. Credit cards, personal loans and many auto loans cost more than a mortgage. Paying those first is arithmetic, not preference.
- An employer match is on the table. An unmatched retirement contribution is a guaranteed return you are declining.
- You are still paying PMI. The same money aimed at 80% loan-to-value can cancel a charge that buys you nothing, which our guide to PMI removal walks through.
- You want a lower payment, not a shorter loan. Extra principal shortens the term without moving the monthly payment. To convert a lump sum into a smaller payment you need a recast.
The mortgage interest deduction changes this calculus for fewer households than it used to, because most filers now take the standard deduction and deduct no mortgage interest at all. If you do itemize, prepaying reduces a deduction you were using; IRS Publication 936 sets out the rules. We are not tax advisors or financial advisors — this is general information, and a HUD-approved housing counselor will review a household budget free of charge.
Frequently asked questions
Does paying extra lower my monthly payment?
No. It shortens the loan instead. The payment on a fixed-rate mortgage is set by the original balance, rate and term, and it stays there until the loan is paid off, refinanced or re-amortized. Only a recast or a refinance moves the payment down.
Is it better to pay extra or to refinance into a 15-year loan?
Extra payments keep the flexibility: in a bad month you simply pay the normal amount. A 15-year loan usually carries a lower rate but locks in the higher payment, with closing costs to get there. Our 30-year versus 15-year comparison runs both sides.
Does paying off my mortgage early hurt my credit score?
Closing any installment account can nudge a score down slightly by removing an active, well-paid tradeline and thinning the credit mix. The effect is normally small and temporary, and it is a poor reason to keep a mortgage you can retire.
Should I make one big payment or add a little every month?
Timing beats packaging: interest accrues on the balance every day it exists, so the sooner a dollar lands the more it saves. A lump sum in January outperforms the same total drip-fed across the year, but the difference is modest. The method you will actually keep up with wins.
What happens to my escrow account when the loan is paid off?
The servicer refunds the remaining escrow balance, generally within a few weeks of the payoff, and releases the lien. Taxes and homeowners insurance then become your bills to pay directly and on time — insurance lapses are a common and expensive mistake in the first year after payoff.
Sources
Related: Mortgage recast: lowering the payment without refinancing, 30-year vs 15-year mortgage: the real trade-off, with the numbers, Rate-and-term refinance: when it pays, how to compute the break-even, PMI removal: the 80% request, the 78% automatic cancellation, and the appraisal route. Hub: Conventional loan.