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CalcTortoise

Compound Interest Calculator

See how money grows when interest earns interest, how the compounding frequency changes the result, and what monthly deposits add.

Written by the CalcTortoise editorial team · How we work

years

Interest added

How often interest is added to the balance so it starts earning interest too.

Value after 10 years

$16,470

With monthly compounding, 5% is really 5.12% a year. Interest on interest adds $1,470 over simple interest.

Money put in
$10,000
Interest earned
$6,470
Effective yearly rate
5.12%
Extra over simple interest
$1,470

Illustration only, not investment, tax or legal advice.

What the final amount is made of
  • Money put in$10,000 (60.7%)
  • Interest$6,470 (39.3%)
Compound against simple interestMonthly compoundingSimple interest

Year by year

YearPut inInterestBalance
Year 1$10,000$512$10,512
Year 2$10,000$1,049$11,049
Year 3$10,000$1,615$11,615
Year 4$10,000$2,209$12,209
Year 5$10,000$2,834$12,834
Year 6$10,000$3,490$13,490
Year 7$10,000$4,180$14,180
Year 8$10,000$4,906$14,906
Year 9$10,000$5,668$15,668
Year 10$10,000$6,470$16,470

How to use this calculator

  1. Enter the starting amount and the annual interest rate.
  2. Choose the period and how often interest is added.
  3. Add a monthly deposit if you will keep saving.

Frequently asked questions

What is compound interest?

Interest that is added to the balance and then earns interest itself. $10,000 at 5% compounded monthly reaches $16,470 after 10 years, against $15,000 with simple interest.

What is the effective annual rate (AER)?

The yearly rate once compounding is included: 5% compounded monthly is 5.12% a year. It lets you compare accounts that compound at different intervals.

Does it work in my currency?

Yes. The calculation is the same everywhere; pick your currency at the top of the page if you want its symbol shown.

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