Free financial calculators that show their math
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$10,000 + $200/month at 7% for 20 years
$144,572.72
- Your deposits $58,000.00
- Interest $86,572.72
Calculators
Compound Interest Calculator
Project an initial investment plus monthly deposits with any compounding frequency, and see every year of growth.
Open calculatorSavings Goal Calculator
Find the monthly amount needed to reach a target by a set date, or how long it takes at what you can save.
Open calculatorDaily Compound Interest Calculator
Grow a balance at a daily or yearly rate, with a reinvest rate and weekday-only compounding, day by day.
Open calculatorComing soon: Inflation Calculator · Investment Growth Calculator
How we build our calculators
The math is on the page
Each calculator explains its formula, its assumptions and what it leaves out, with worked examples you can reproduce.
Tested before it ships
Calculations are checked against textbook formulas and edge cases such as a 0% rate or a 100-year horizon before a calculator goes live.
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Results are calculated in your browser. We do not save the numbers you enter, and there is no account to create.
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Why compound interest is worth understanding
Compound interest pays interest on your interest. In the example above, $86,572.72 of the final $144,572.72 came from interest rather than deposits. The longer money stays invested, the larger that share becomes.
The compound interest calculator lets you test the levers that matter: how much you start with, how much you add each month, the rate, how often interest compounds and how long you stay invested. Working toward a target? The savings goal calculator tells you how much to put away each month. Interested in daily growth, from a savings account or a daily return? Try the daily compound interest calculator.