Pay Off Mortgage Early vs Invest Calculator

Before you run this calc: if you're not yet capturing your full employer 401(k) match, stop and do that first. A 100% return on your match contribution beats both options below. Same for an HSA contribution if you're eligible. This calculator is for what to do with the next dollar AFTER those.

Extra you can pay monthly ($) Money you'd either put toward the mortgage OR invest. Same dollar amount either way. Current mortgage rate (%) Years remaining on mortgage Current mortgage balance ($) Do you itemize deductions on your taxes? Since 2017 the standard deduction went up dramatically — most households no longer itemize. If you take the standard deduction, mortgage interest gives you zero tax benefit. Your marginal federal tax bracket (%) Common: 12% (~$45k-$100k MFJ), 22% (~$100k-$210k MFJ), 24%, 32%. Expected annual investment return (%, nominal pre-tax) S&P 500 long-term nominal average is ~10%. Conservative balanced portfolio is ~6-8%. Use a number you'd be comfortable defending if it didn't come true. Investment account tax treatment How long until you'd compare results? (years) Both strategies need years to play out. Shorter horizons favor the mortgage; longer horizons favor investing.

How this works

The calculation has three steps:

Effective mortgage rate. If you itemize, your effective rate is nominal × (1 − marginal tax rate). If you take the standard deduction, your effective rate equals your nominal rate. Most US households take the standard deduction post-2017.
After-tax investment return. Roth = your stated return. Taxable = your return minus long-term capital gains tax (15% for most). Traditional = your return on the way up, then taxed at your retirement bracket on the way out (we estimate this conservatively).
Wealth at horizon. For "pay mortgage": project the months saved off the loan plus the cash freed up by being mortgage-free. For "invest": project the future value of the same monthly contribution. Compare net wealth at your stated horizon.

The hidden answer most calculators miss: if you're not itemizing and your mortgage is over 6%, paying the mortgage off early often wins — because the mortgage interest isn't tax-deductible for you, so the comparison is your 6.5% guaranteed (paying off) vs your ~6% after-tax (taxable account) or ~7.5% (Roth). At those numbers, the guaranteed return wins for most risk profiles.

What the math can't decide for you

Sleep-at-night value. A paid-off house removes a major financial stressor. The math doesn't price that; you do.
Discipline. Will you actually invest the difference, every month, through a 30% market drawdown without stopping? If yes, the math holds. If you'd panic-sell, paying the mortgage is the more honest answer.
Liquidity. Investments are accessible. A paid-off house is not. If you might need that money before the horizon, the investment path keeps options open.
Insurance / job security. A paid-off house is one form of self-insurance against income loss. Investments are not (you can't pay a mortgage with a 401(k) without penalties).

Tools for the next move

Open an investment account See current mortgage rates

Related calculators

Bi-weekly mortgage payments — the most common "pay down faster without committing to a refi" path. Run it before deciding to fully accelerate payoff.
30-to-15 year refinance — the locked-in version of "pay down faster." Captures most of the same interest savings but forces the discipline.
Refinance to remove PMI — if you're still paying PMI, that's a guaranteed return that beats both paths above.

FAQ

Why does this calculator factor in tax-deductibility when most don't?

Because for many borrowers it changes the answer. If you take the standard deduction — most households since 2017 — mortgage interest gives you zero tax benefit, so your effective mortgage rate equals your nominal rate. If you itemize, your effective rate is lower, which changes the comparison.

What investment return should I assume?

The S&P 500's nominal long-term average is about 10%, real (after inflation) is about 7%. For an honest comparison against a nominal mortgage rate, 7-8% is defensible. Use a number you'd be comfortable defending to a future version of yourself who lived through a sequence of bad returns.

Doesn't paying off the mortgage give a guaranteed return?

Yes — your effective return is your effective mortgage rate, with certainty. That certainty has real value, especially for risk-averse households or anyone near retirement. The math here treats it as risk-free; the verdict factors in your stated risk preference.

What about emotional / behavioral factors?

Real. A paid-off house removes a major source of financial stress. Investing requires discipline that many people don't have in a downturn. The verdict notes when these factors should override the pure math.

Does this calculator handle 401(k) match or HSA contributions?

Not directly. The priority order before either path: max your 401(k) match (100% return), max your HSA (triple tax advantage), then come back here for what to do with the remainder.

What if my mortgage is at 3.5%?

The math almost always favors investing at that rate — but only if you'll actually invest it. The 2020-2021 sub-3% mortgages are essentially free money in inflation-adjusted terms. Keep them, invest the extra. Calculator will confirm.