Skip to content
CalcTortoise

Compound Interest Calculator

Find out how much your money grows when interest earns interest, how compounding frequency changes the result, and what regular contributions 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

Compounding monthly, 5% works out to 5.12% a year — and earns you $1,470 more than simple interest.

Total deposits
$10,000
Interest earned
$6,470
APY (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 your starting balance and the annual interest rate.
  2. Choose how long you’ll leave it and how often interest compounds.
  3. Add a monthly contribution if you plan to keep saving.

Frequently asked questions

How does compound interest work?

Interest is added to your balance, and from then on it earns interest too. $10,000 at 5% compounded monthly grows to $16,470 in 10 years — $1,470 more than simple interest would pay.

What’s the difference between APR and APY?

APR is the stated yearly rate; APY includes compounding. A 5% rate compounded monthly has an APY of 5.12%; compounded daily, 5.13%.

How much do regular contributions add?

A lot. Adding $200 a month to the same $10,000 at 5% takes it to $47,656 after 10 years.

Is interest taxable?

Interest from savings accounts and CDs is generally taxable in the year it’s credited, unless it’s earned inside a tax-advantaged account. Figures here are before tax.

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

Related calculators

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