EXAMPLE
$5,000 at 5% for 10 years with $100/month added grows to about $23,763.
Enter an amount and years to see results.
Ad — 728×90
How this calculator works
Money that earns interest on interest grows faster than most people expect, especially over long periods — that is the idea behind compound interest. This calculator shows how a starting amount grows over time, with or without regular contributions along the way.
THE MATH BEHIND IT
Growth on starting amount: Principal × (1 + rate ÷ periods)^(periods × years)
Growth from contributions: same compounding, applied to each deposit
Interest earned: Final amount − everything contributed
A real example
$5,000 invested at 5% annual interest, compounded monthly, for 10 years, with $100 added every month:
Starting amount grows to
≈ $8,235
Contributions grow to
$100/mo × 120 months, compounded =≈ $15,528
Total after 10 years
$8,235 + $15,528 =≈ $23,763
Interest earned
$23,763 − $17,000 contributed =≈ $6,763
Common questions
More frequent compounding (daily versus yearly) means interest gets added to the balance more often, so interest starts earning interest sooner. The difference is usually small but measurable over long periods.
Simple interest grows based only on the original amount. Compound interest grows based on the original amount plus all interest already earned, which is why the growth curve gets steeper the longer the money is invested.
Contributions compound too, not just the starting balance — so consistent deposits over many years can account for more of the total growth than the initial lump sum.