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CalcTortoise

Repay or Invest Calculator

Overpay the loan, or invest the money? Compare where you end up both ways, and the return an investment would need to come out ahead.

Written by the CalcTortoise editorial team · How we work

years

After each extra instalment

If you invest it

Your loan rate is 6% — the return investing has to beat, before tax.

Overpaying comes out ahead by

$0

Overpaying the loan comes out ahead by $0. Investing would need more than 6% a year to win.

Illustration only, not investment, tax or legal advice. Returns are assumed, not predicted.

Overpay the loan

$138,612

what you have after 20 years

  • Loan paid off in 14 years 5 months
  • Interest saved: $44,890
  • After that, the freed-up payment is invested too

Invest the money instead

$138,612

what you have after 20 years

  • Loan runs the full 20 years
  • $0 now and $300 a month invested
  • Total interest: $143,887
What you have, year by year (investments minus the loan)Overpay the loanInvest the money instead

Year by year

YearLoan left · overpay the loanInvested · overpay the loanLoan left · invest the money insteadInvested · invest the money instead
Year 1$190,960$0$194,660$3,701
Year 2$181,362$0$188,991$7,630
Year 3$171,172$0$182,973$11,801
Year 4$160,354$0$176,583$16,229
Year 5$148,868$0$169,799$20,931
Year 6$136,674$0$162,597$25,923
Year 7$123,728$0$154,950$31,222
Year 8$109,984$0$146,832$36,849
Year 9$95,391$0$138,213$42,822
Year 10$79,899$0$129,063$49,164
Year 11$63,451$0$119,348$55,897
Year 12$45,989$0$109,034$63,045
Year 13$27,450$0$98,084$70,634
Year 14$7,767$0$86,458$78,691
Year 15$0$13,130$74,116$87,246
Year 16$0$35,316$61,012$96,327
Year 17$0$58,870$47,100$105,969
Year 18$0$83,876$32,329$116,206
Year 19$0$110,426$16,648$127,074
Year 20$0$138,612$0$138,612

How to use this calculator

  1. Enter the balance outstanding, the interest rate and the years left.
  2. Enter your spare money — monthly, a lump sum, or both.
  3. Choose where you would invest it and the return you expect.

Frequently asked questions

Is it better to overpay a loan or invest?

It depends on how the investment return compares with the loan rate. With $300 a month spare on $200,000 at 6%, investing at 6% falls behind overpaying by about $0 after 20 years; the break-even return is 6%.

Why is overpaying a “certain” return?

Each amount repaid stops costing 6% interest whatever the markets do. An investment may earn more, but it may also earn less.

Is tax included?

No. Tax relief on loan interest, or tax on investment returns, changes the break-even point and differs by country.

Sources and method

Standard compound-interest formulas, tested against worked examples. Nothing here depends on outside data; the rates you type in are your own assumptions.

No outside data is used. The numbers you type in are the only inputs.

Page and formula last reviewed . How we calculate · Editorial policy · Corrections and change log

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Last updated 9 October 2026. For information only — not financial advice. Check the final figures with your lender or bank.