Mortgage Extra Payment Calculator
Apply extra principal to your mortgage (monthly / annual / lump sum). See years off the loan + total interest saved + payoff date.
Mortgage Extra Payment Calculator
Your mortgage
Extra principal payments (set any or all)
Baseline (no extra) vs accelerated payoff
How to use the Mortgage Extra Payment Calculator
Enter your current mortgage
Current balance (not original loan amount — your CURRENT balance), interest rate (the rate, not APR), and remaining term in years. For a 30-year loan with 2 years already paid, enter 28 years remaining.
Choose your extra-payment strategy
Three ways to accelerate, each combinable. Extra per month: simplest — add $100, $200, $500 to every monthly payment. Extra per year: applied each December (e.g., tax refund, year-end bonus). Lump sum: one-time large payment (inheritance, bonus, sale of asset).
Read years saved + interest saved
The hero number is years saved off the loan. The interest saved is total dollars NOT paid to the lender. For a typical $350K mortgage at 6.5%, $200/month extra saves about 6 years and $70K in interest — a 4-5× return on the extra principal you paid.
Compare against investing instead
Critical question: is paying extra principal better than investing the same money? Rule of thumb: if your mortgage rate > your expected real investment return, payoff wins. At 7%+ mortgage rates, payoff almost always beats investing. At 3-4% mortgage rates with index investing, the math often favours investing. The tool gives you the payoff side; you compare against your alternative.
Extra mortgage payments — the highest-leverage debt move most homeowners ignore
Every dollar of extra principal you pay on a mortgage skips ALL the future interest that dollar would have accrued. On a 30-year mortgage at 7%, $1 of extra principal in year 1 saves approximately $5 of future interest over the life of the loan. That's a 500% return on the extra dollar — risk-free, tax-favoured (the foregone interest was after-tax dollars), and immediately effective. Few financial moves match it, especially in high-interest-rate environments. The math is so elegant that aggressive payoff is one of the few cases where you can mathematically prove it's better than investing — when the mortgage rate exceeds your realistic investment return.
How extra payments compound
A standard 30-year mortgage at 6.5% on $350K has a monthly payment of about $2,212. Over 30 years you pay $796K total — $446K of which is interest. Now add $200 extra per month from day one. The accelerated payoff finishes in 22.5 years instead of 30 — saving 7.5 years and roughly $115K in interest. You paid an extra $54K in principal over those 22.5 years and got back $115K in interest savings — a 2.1× return. Earlier payments compound more savings because they remove principal that would otherwise accrue interest for the longest time. $200/month in years 1-5 saves far more than $200/month in years 25-30.
On a 30-year mortgage at 7%, $1 of extra principal in year 1 saves ~$5 of future interest. That's a 500% return — risk-free, immediate, tax-favoured. Few financial moves match it.
The APAC mortgage angle
Mortgage acceleration math is universal but the trade-offs differ regionally. Singapore's mortgage rates have run 2.5-4% historically — relatively low, which weakens the payoff case vs investing. Malaysia's housing loans 3.5-4.5%. Indonesia 7-10%. Vietnam 9-12%. The Philippines 6-9%. Thailand 3-5%. In the 2022-2025 era of higher global rates, even Singapore mortgages have climbed to 4-5% — making extra payments more attractive. The general rule: if your mortgage rate is below 5%, the investing-vs-payoff math is genuinely close; above 6%, payoff usually wins; above 7%, payoff almost always wins.
When NOT to make extra payments
Three situations to skip the extra payment strategy. (1) You have higher-interest debt — credit card at 18-25% absolutely takes priority over a 6% mortgage. (2) You don't have an emergency fund yet — extra mortgage payments are illiquid (you can't easily get the money back if you need it). Build 3-6 months emergency fund first. (3) Your mortgage rate is below your tax-advantaged investment opportunity cost — a 3% mortgage in 7% long-term real return territory means you're giving up 4% real return per year by accelerating. Run the comparison both ways and pick consciously.
10 Things to Know About Mortgage Acceleration
On a 30-year mortgage at 7%, $1 of extra principal in year 1 saves ~$5 of future interest. The return drops as the loan ages (year 25 extra saves only ~$0.20).
The "bi-weekly trick": pay half the monthly amount every 2 weeks → 26 half-payments = 13 full payments per year. Knocks ~7 years off a 30-year mortgage. See our Bi-Weekly Calculator.
Some lenders charge prepayment penalties — typically 1-3% of the prepaid amount, declining over 3-5 years. Check your mortgage documents before making large extra payments.
Extra payments must be designated as principal-only with most lenders — otherwise they may be applied as the next month's payment in advance. Always check your statement.
The mortgage interest deduction (US only, capped at $750K post-2018) means the after-tax effective rate on your mortgage is lower than the nominal rate — reduces the payoff-vs-invest case slightly for high earners.
In Singapore, CPF Ordinary Account funds can be used to pay down HDB mortgage — but at the opportunity cost of CPF Special Account compounding at 4-5% guaranteed.
The "15-year refinance" achieves similar interest savings as extra payments but locks you into the higher monthly payment. Extra payments preserve flexibility (you can stop in lean months).
A typical $300K mortgage at 6% saves about $100K in interest with $200/month extra payments. That's a 50× return on the $200 the borrower paid extra.
In the 2020-2021 ultra-low-rate era (2.5-3% mortgages), extra payments became mathematically inferior to investing — many homeowners deliberately KEPT their mortgages to invest the differential.
Psychological argument for extra payments: debt-free is debt-free. Investing the extra produces a higher expected return but exposes you to market risk and behavioural risk (will you actually invest it consistently?). Payoff is guaranteed and certain.
Frequently Asked Questions
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Depends on your mortgage rate vs realistic investment return. Rule of thumb: if mortgage rate > your expected real investment return, payoff wins. At 7%+ mortgage rates, payoff almost always beats investing. At 3-4% rates, investing often wins (long-term real S&P 500 is ~7%). Mixed approach: split the extra 50/50.
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Yes, in almost all cases — but check for prepayment penalties first. US mortgages from 2014+ generally have no prepayment penalty. Some commercial loans and some 2008-era loans did. ALWAYS designate extra payments as "principal only" — otherwise some lenders apply them as next-month-paid-ahead, which doesn't save you any interest.
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EARLIER. A $1 extra payment in year 1 of a 30-year mortgage saves ~$5 future interest. The same $1 in year 25 saves ~$0.20. Earlier extra payments remove principal that would otherwise accrue interest for the longest remaining time. If you're 25 years into a 30-year mortgage, extra payments still save some money but the leverage is much weaker.
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Refinancing changes the loan: new rate, new term. Extra payments keep the same loan but pay it faster. Refinancing makes sense when rates have dropped significantly (~1% or more lower); extra payments make sense when you can afford more than the minimum and want to pay down faster without committing to a new contract. Extra payments preserve flexibility (you can stop); refinancing locks in the new payment.
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Yes if your mortgage rate exceeds the rate you'd get on tax-advantaged savings. Tax refunds are "found money" psychologically — easier to commit to mortgage payoff than to cut everyday spending. Combining annual tax-refund lumps with consistent monthly extras typically halves payoff time on a 30-year mortgage.
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Slightly, for itemisers. The deduction lowers your effective after-tax mortgage rate. A 6.5% nominal rate at a 24% marginal tax bracket is effectively 4.94% after-tax. Note: post-TCJA 2018, fewer Americans itemise (most take the standard deduction), so the deduction often doesn't apply at all. Always run the after-tax math for your specific situation.
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You can use CPF OA (2.5% guaranteed) to pay down HDB mortgage (typically 2.6% or 2.6% concessionary rate). Mathematically: 0.1% spread for taking the money out of compounding. Not worth it unless cash flow demands. CPF SA (4% guaranteed) should NEVER be used for housing — opportunity cost is enormous over 30 years.
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Some lenders allow "recasting" after a large lump sum — they recalculate the monthly payment to amortise the new lower balance over the remaining term. Costs typically $250-500. Reduces your monthly payment without changing the rate or term. Useful after a big windfall + you want lower monthly burden vs faster payoff.
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Because extra payment timing matters. A closed-form formula for "years saved" doesn't exist when you have multiple extra-payment types (monthly + annual + lump). Month-by-month simulation captures the exact amortisation correctly and works regardless of how you mix the three payment types.
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No. All calculation happens entirely in your browser via JavaScript. Open DevTools → Network and watch — there's zero outbound traffic.
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