Pay Off Mortgage or Invest? Calculator & Guide (2026)
Pay off your mortgage or invest extra cash? Compare known interest savings with uncertain after-tax returns using the same monthly budget in a calculator.
Pay off mortgage or invest? There is no universal winner. Extra principal produces a known interest saving at your loan rate, while investing has uncertain, after-tax returns. Compare the same cash flow after taxes, fees, liquidity, market risk and any prepayment rules; the mortgage comparison calculator is a scenario, not a forecast.
Compare extra-principal payoff with an investment scenario using the same balance, rate, term and monthly surplus assumptions.
Paying more than the required monthly mortgage payment, with the extra applied to principal to shorten the loan and reduce future interest.
Example: $300,000 balance, 30-year fixed at a 6% note rate, with $300 extra each month: about $1,798.65 scheduled principal-and-interest, payoff in 21 years, and roughly $119,701 less interest under a monthly note-rate/12 model, before taxes or fees.
The possible value given up by using cash for one financial choice instead of its next-best alternative.
Example: Cash sent to extra principal is unavailable to invest; any investment return is uncertain and may be negative.
Should you pay off your mortgage early or invest? Compare the interest your extra payments could avoid with the uncertain, after-fee result of investing the same cash. Your loan terms, tax situation, time horizon, need for liquid savings and comfort with market losses all matter; no single rate cutoff works for every household.
Worked illustration: on a $300,000 fixed-rate loan amortized over 30 years at a 6% note rate, the scheduled principal-and-interest payment is about $1,798.65 per month. Applying another $300 to principal each month from the start pays the modeled loan off in 252 months instead of 360 and reduces total interest by about $119,701. This calculation uses a monthly interest rate equal to the note rate divided by 12 and excludes taxes, fees and payment-posting differences; your lender statement may differ.
Pay extra on the mortgage vs invest — run your numbers
Same spare cash, two paths over your remaining term. Path A sends the extra to the mortgage, then invests the freed-up payment after payoff. Path B keeps the normal payment and invests the extra every month.
Any unused amount from the final payoff payment is invested that month; the full payment + extra is invested after payoff until the original term ends.
The extra is invested every month for the whole term; the mortgage runs on schedule.
Break-even: an investment return of about 6% (your mortgage rate) makes both paths equal. The math is close — the guide below explains why taxes and risk shift it.
Illustrative fixed-rate model: divides the mortgage note rate and assumed nominal investment return by 12, with investment deposits at month-end. Any unused amount from the final payoff payment is invested that month. The displayed payment covers principal and interest only. Taxes, fees, inflation, changing returns and prepayment penalties are excluded; the investment return is an assumption, not a forecast.
How the calculator compares the two choices
Enter your remaining balance, mortgage rate, time left, monthly surplus and an assumed investment return. The calculator models the mortgage rate and investment return as fixed monthly rates. One path sends the surplus to principal, then invests the former payment after the loan is paid; the other follows the normal mortgage schedule and invests the surplus each month. It compares the portfolio at the original end date, not a complete household net-worth plan.
This is a scenario tool, not a forecast: it does not model taxes, investment fees, inflation, changing returns, escrow, prepayment penalties or your actual payment-posting schedule. Test several return assumptions instead of treating one selected rate as expected or guaranteed.
If you need to compare calculators before choosing one, see the best mortgage calculators comparison, which documents whether each tool exposes extra payments, PMI/PITI, amortization, refinancing, charts and sharing. Provider interfaces and terms can change, so verify the fields you need.
Factors that can change your comparison
- Loan terms: confirm how extra payments are applied to principal and whether your note includes a prepayment penalty.
- Taxes: the mortgage-interest deduction applies only when the borrower and loan meet current IRS rules; do not assume every homeowner receives the same tax benefit.
- Risk and liquidity: investments can lose value, while extra principal becomes home equity and is less accessible than cash in an account.
- A split is also possible, but this calculator compares the two all-in paths and does not select or model an ideal percentage split.
Further reading and sources
Our 5,000-scenario mortgage prepayment study is a separate sensitivity analysis, not a prediction. You can also compare mortgage calculators by extra-payment inputs, PMI/PITI, amortization and refinancing features before choosing a tool. For your own decision, use your loan note, current tax guidance and investment disclosures.
Frequently asked questions
Should I pay off my mortgage early or invest?
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Does the mortgage-interest tax deduction change the comparison?
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Could my lender charge a fee for paying the mortgage early?
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Can I invest and pay extra principal at the same time?
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Does a higher assumed stock return mean investing will win?
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Plug in your own amounts with our free calculators.