Compound Interest Calculator

A compound interest calculator projects how savings grow when interest is earned on both the deposit and past interest. This free tool applies A = P(1 + r/n)^(nt), adds monthly or yearly contributions, and shows the future value, interest earned, effective annual yield and a year-by-year table. For example, $1,000 at 5% compounded yearly for 10 years grows to $1,628.89.

Free, no signup. Runs entirely in your browser; files and text are not uploaded.

How to use the Compound Interest Calculator

  1. Enter your initial investment, the annual interest rate and the number of years.
  2. Choose how often interest compounds, from annually to daily.
  3. Optionally add a regular contribution, choose monthly or yearly, and whether it is made at the start or end of each period.
  4. Read the future value, total contributions, interest earned and effective annual yield (APY).
  5. Scroll the Growth by year table to see the balance at the end of every year.

Features

  • Annual, semi-annual, quarterly, monthly or daily compounding
  • Monthly or yearly contributions, made at the start or end of each period
  • Future value, total deposited, interest earned and APY
  • Year-by-year growth table, including fractional final years
  • Contribution growth uses the rate implied by the chosen compounding frequency
  • Currency selector and validation for empty or negative values

Frequently asked questions

What is the compound interest formula?

A = P(1 + r/n)^(nt), where P is the principal, r the annual rate as a decimal, n the number of compounding periods per year and t the number of years. Regular contributions are added with the future value of an annuity formula.

How much will $1,000 grow at 5% for 10 years?

Compounded yearly, $1,000 grows to $1,628.89. Compounded monthly it grows to about $1,647.01 because interest is added more often.

What is the difference between APR and APY?

APR is the stated annual rate. APY is the effective annual yield after compounding: (1 + r/n)^n − 1. A 5% rate compounded monthly has an APY of about 5.116%.

Does it matter if I contribute at the start or end of the month?

Yes. Contributions made at the start of each period earn one extra period of interest, so the future value is slightly higher than with end-of-period contributions.

Related tools

  • Loan Calculator – Monthly, bi-weekly or weekly loan payments, total interest, extra payments and an amortization schedule.
  • Percentage Calculator – Percent of a number, percentage change, increases, discounts and more
  • Tip Calculator – Work out the tip, the total and what each person pays when you split the bill.
  • Currency Converter – Convert 50+ currencies with daily mid-market exchange rates

Built and reviewed by Naqash Thaheem, Technical Project Manager. Last reviewed 2026-09-24.