Compound interest calculator
Model contributions, rate, and time with instant feedback and a clear growth chart.
100% client-side. Your inputs stay in this browser.
Drag sliders or type numbers. The chart updates as you change inputs.
Future value
$343,778
Total contributed
$130,000
Interest earned
$213,778
Multiplier
2.64×
How this tool works
We use the standard compound future-value formula with periodic contributions converted to your compounding frequency. When the rate is zero, growth is linear (contributions only). When years is set to zero, the result is your starting balance.
Frequently asked questions
What is compound interest?
Compound interest is interest on your initial amount and on accumulated interest from earlier periods. It grows faster than simple interest because the base keeps increasing.
Does my data get sent anywhere?
No. This calculator runs entirely in your browser. Nothing you type is sent to our servers.
How often should interest compound?
Many savings products compound monthly or daily. Bonds may use annual compounding. More frequent compounding slightly increases the ending balance for the same rate.
Related tools
More calculators will appear here as we ship them from the OnSumo roadmap (mortgage amortization, rent vs buy, FIRE tracker, and others).