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Enter your mortgage and a monthly amount to allocate. See the net worth of paying down extra principal versus investing the same money in a 401(k), Roth IRA or taxable brokerage — which wins, by how much, and your personal break-even return.
8 min readUpdated 6 Sep 2026United States (USD)
Your details
$
%
yrs
30-year fixed is the US standard
$/ mo
Extra principal, or invested — after any 401(k) match
%
US stock index funds: ~7-10% historically
Tax-advantaged — modeled as tax-free growth
Only if your itemized deductions beat the standard deduction (acquisition-debt cap applies)
Used to value the mortgage interest deduction
Results
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Enter your details to compare investing vs paying off your mortgage.
Enter your mortgage, a monthly amount to allocate and your expected return, then choose your account type to see which strategy wins and your personal break-even return.
Net worth over time
Comparing both strategies to original term end
Invest
Pay off mortgage
Key takeaways
Capture your full employer 401(k) match first. A 50-100% instant return beats both extra principal and taxable investing.
Paying down is a guaranteed return equal to your mortgage rate. Investing offers higher but uncertain returns.
The break-even return is the deciding number. Beat it and investing wins; fall short and paying down wins.
A Roth IRA or 401(k) tilts it toward investing. Tax-free growth pushes the break-even close to your mortgage rate; a taxable account raises it.
The mortgage interest deduction only helps if you itemize. Most filers take the standard deduction, so for them it does not change the math.
Pay down your mortgage or invest? A US guide to the decision
By CalculatorDashboard Editorial Team·Updated ·Reviewed ·6 min read
Should you pay off your mortgage or invest?
It comes down to your numbers: paying down extra principal earns a guaranteed return equal to your mortgage rate, while investing offers higher but uncertain returns. Every dollar you put toward the balance saves you that rate in interest for every remaining year of the loan — with no uncertainty about what you'll save.
Worked example: the calculator's default is a $400,000 mortgage at 6.5% with $500 a month to allocate, invested at 7% in a tax-advantaged account over 30 years. Because the 30-year horizon lets compounding run, investing typically comes out ahead, and the break-even return sits just above the mortgage rate. Switch to a taxable brokerage and the break-even climbs, because long-term capital gains tax (and possibly the 3.8% NIIT) eats into your return.
Historically a globally diversified US stock index fund has returned roughly 7-10% a year in nominal terms over long periods, comfortably above most fixed mortgage rates. But those returns come with volatility: in any single year the market can fall 30-40%, and the sequence of returns matters, especially over shorter horizons.
Before either choice, one move beats both: capture your full employer 401(k) match. A dollar-for-dollar or 50-cent match is an instant 50-100% return that no mortgage rate can match. Only direct spare cash to extra principal or a taxable account after the match is maxed.
This calculator runs both scenarios month by month to the end of your original loan term and compares net worth at that point. It also solves for the exact break-even investment return — the rate at which both strategies produce the same outcome. Enter your details to see the numbers for your situation.
Guaranteed return vs expected return
When you pay down your mortgage, you earn a guaranteed, risk-free return equal to your mortgage rate. On a 6.5% loan, every dollar of extra principal saves 6.5 cents a year in interest until the loan is cleared — better than most savings accounts and completely certain.
When you invest instead, you trade that certainty for the potential of higher returns. A diversified US equity index fund has historically returned about 7-10% a year over long periods — but with real volatility along the way.
The break-even rate is the investment return at which both strategies produce identical net worth at your loan's term end. If you can confidently earn more than the break-even rate, invest. If not, pay down.
In a Roth IRA or 401(k) (no tax on growth), the break-even is close to your mortgage rate. In a taxable brokerage account, capital gains tax raises the break-even — you need a higher gross return to end up with the same after-tax result.
How US taxes change the decision
Tax-advantaged accounts. A Roth IRA grows and is withdrawn tax-free — the cleanest comparison against a paid-off mortgage. A Traditional IRA or 401(k) is tax-deferred: you deduct contributions now but pay ordinary income tax on withdrawals. This tool models tax-advantaged accounts as tax-free growth; for Traditional/401(k) money, remember withdrawals will be taxed, which trims the real edge slightly.
Taxable brokerage. Long-term capital gains are taxed at 0%, 15% or 20% depending on income, and higher earners may owe an extra 3.8% net investment income tax (NIIT). Short-term gains are taxed as ordinary income. This drag raises your break-even return.
Mortgage interest deduction. Unlike many countries, US filers can deduct mortgage interest — but only if they itemize and their itemized deductions beat the standard deduction, and only on acquisition debt up to the current cap. When it applies, the after-tax cost of your mortgage falls to roughly your rate times (1 − your marginal rate), which lowers the guaranteed return from paying down and tilts the decision toward investing. Most households now take the standard deduction, so for them the deduction does not change the math.
Always verify current-year figures. Capital gains brackets, the NIIT threshold, the standard deduction and the mortgage-interest acquisition-debt cap change over time. Confirm the numbers for your tax year before acting. This is educational information, not tax or investment advice.
When does paying off the mortgage win?
High mortgage rate. At 6.5-7%+, that is a high, guaranteed hurdle for uncertain returns to beat.
Short remaining term. With 5-8 years left, compounding has little time to overcome the advantage of clearing the loan early.
Taxable account. Capital gains tax raises your effective break-even rate.
Near or in retirement. A guaranteed, debt-free retirement can be worth more than uncertain extra returns.
Peace of mind. Some people simply sleep better without a mortgage. That value is real.
When does investing win?
Long horizon. With 15-30 years, compound growth has time to outpace the mortgage rate.
Roth IRA or 401(k) available. Tax-free growth lowers the break-even.
Low mortgage rate. A sub-4% rate is easy to beat with diversified equities.
Employer match. Always take the free match first — a 50-100% instant return.
Young investor. Time in the market is the biggest driver of long-term wealth.
How do the outcomes compare across scenarios?
The winner flips with your rate, account type and horizon — here's how five common US setups play out at a 7% expected return:
Scenario
Mortgage rate
Inv. return
Account
Winner
Low rate, Roth/401(k)
3.5%
7%
Tax-adv.
Invest
Mid rate, Roth/401(k)
5.0%
7%
Tax-adv.
Invest
Mid rate, taxable
5.0%
7%
Taxable
Close
High rate, short term
7.0%
7%
Taxable
Pay off
High rate, long term
6.5%
8%
Tax-adv.
Invest (marginal)
Should you do both — a blended approach?
Yes — you don't have to choose one strategy completely. Many people split spare cash, say 60% to a Roth IRA and 40% to extra principal. This hedges both ways: if markets have a bad decade you've still cut your debt, and if they do well your portfolio grows. The progress-on-both-fronts feeling is underrated, and it's a reasonable default when the mortgage rate and expected return are close.
How US rules change the comparison
Three features of the US system shape the decision differently from the UK. First, most US mortgages are 30-year fixed loans with no prepayment penalty, so extra payments can be made at any time and the rate never changes. Second, many employers match 401(k) contributions, and an employer match is usually a better return than any mortgage paydown: a 50% match is a 50% return before any investment growth. Third, mortgage interest is only deductible if you itemize, and most households now take the standard deduction, so the deduction often makes no difference at all.
A worked example: $20,000 against a 6.5% mortgage
Alex has $20,000 spare and a 30-year mortgage at 6.5% with 25 years left. Paying it down earns a guaranteed 6.5% a year. Over 25 years that's equivalent to about $96,550. Investing the same amount in a diversified index fund inside a Roth IRA, where growth is tax-free, would reach about $136,970 at an 8% average return, but nothing about that return is guaranteed. At 6.5%, a high-rate mortgage sets a demanding bar for investing to beat after fees.
The usual order for US households is: capture the full 401(k) match first, build an emergency fund, clear high-interest debt, then weigh extra mortgage payments against further retirement saving. This is general information, not personal financial advice.
Common questions
Invest or Pay Off Mortgage FAQs (US)
Compare the guaranteed return from paying down (your mortgage rate) against your expected after-tax return. Historically US equity index funds have returned about 7-10% a year, beating most fixed rates — but investing carries risk while paying down is guaranteed. Capture any employer 401(k) match first, then choose between extra principal and a Roth IRA, 401(k) or taxable account.
The break-even return is the investment rate at which both strategies produce the same net worth at your loan's term end. In a Roth IRA or 401(k) it's close to your mortgage rate. In a taxable brokerage, long-term capital gains tax (0/15/20%, plus a possible 3.8% NIIT) raises the break-even.
Only if you itemize and your itemized deductions beat the standard deduction, and only on acquisition debt up to the current cap. When it applies, your after-tax mortgage cost falls to about your rate times (1 − marginal rate), which lowers the return from paying down and favors investing. Most filers take the standard deduction, so for them it doesn't apply.
Almost always. An employer match is an instant 50-100% return on the money you contribute — that beats paying down even a high-rate mortgage. Contribute at least enough to get the full match before directing extra cash anywhere else.
A Roth IRA grows and is withdrawn tax-free, so it's the closest match to a paid-off mortgage. A Traditional IRA or 401(k) is tax-deferred — deductible now, taxed on withdrawal. This tool treats tax-advantaged accounts as tax-free; for Traditional/401(k) money, remember withdrawals will be taxed, trimming the edge slightly.
When the guaranteed saving is high or your horizon is short: a high rate (6-7%+), a short remaining term, a taxable account with real capital gains tax, being near retirement, or heavily valuing the certainty of being debt-free.
Yes — a split hedges both ways. Putting, say, 60% into a Roth IRA and 40% toward extra principal builds wealth through compounding while cutting debt. Many advisors suggest this when the mortgage rate and expected return are close.
This calculator is for illustrative and educational purposes only and does not constitute tax, investment or financial advice. Investment returns are not guaranteed and your capital is at risk. Tax rules and thresholds (capital gains brackets, NIIT, the standard deduction and the mortgage interest deduction cap) change — verify current-year figures for your situation. Always consult a qualified tax or financial professional before making investment or mortgage decisions.