Compound interest calculator

See how your savings and monthly contributions can grow over time, in future and today's dollars.

Growth over time

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How compound interest works

Compound interest means you earn returns on your original money and on the returns already earned. This calculator adds your monthly contribution and applies one-twelfth of the annual return each month, so growth builds on itself over time.

Why time matters most

Starting earlier often beats investing more later. Money invested for 30 years has far more time to compound than the same money invested for 20. Try changing only the years to see the effect.

Nominal vs inflation-adjusted

The future value is in future dollars. The inflation-adjusted figure shows what that money may buy in today's terms, which is a more realistic target for planning.

Frequently asked questions

What return should I use?

Nobody knows future returns. Many planners test a range, such as 4%, 6% and 8%, rather than relying on one number.

Does this include taxes or fees?

No. Fees and taxes reduce real-world results, so consider lowering the return to account for them.

More calculators

Monthly investment calculator: Dollar-cost averaging, yearly increases and a goal planner
Retirement withdrawal calculator: How long your portfolio lasts with inflation-adjusted withdrawals
Roth IRA calculator: Roth vs traditional using your tax rates
FIRE calculator: Your independence number and years to reach it

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