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Compound Interest Calculator

See how savings grow over time with compound interest — choose your compounding frequency and view the growth year by year.

Compound Interest Calculator

Final amount
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Interest earned
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How it works

Compound interest is interest earned on both your original principal and the interest already added — money growing on money. The formula is A = P(1 + r/n)^(nt), where P is the principal, r the annual rate as a decimal, n the number of times interest compounds per year, and t the number of years.

Compounding frequency matters. The more often interest is added, the sooner it starts earning its own interest, so daily compounding produces slightly more than annual compounding at the same nominal rate. The effect is small over one year but grows meaningfully over decades, which is why long-horizon investing is so powerful.

The calculator shows your projected final balance, the total interest earned, and a chart of how the balance climbs year by year. The curve bends upward rather than rising in a straight line — that acceleration is compounding at work. This is a projection using a fixed rate; real returns fluctuate, and it doesn't account for inflation, taxes, or additional contributions.

Examples

$10,000 at 7% for 10 years, monthly → ≈ $20,097.
Same amount at 7% annual vs daily → daily compounding earns slightly more.
Doubling the years far more than doubles the interest — that's compounding.

Frequently asked questions

How does compounding frequency change the result?
More frequent compounding adds interest sooner, so it starts earning its own interest earlier. Daily compounding beats annual at the same rate, though the gap is modest and widens over long periods.
What's the difference between simple and compound interest?
Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus previously earned interest, so it grows faster over time.
Does this include inflation or taxes?
No. It shows nominal growth at a fixed rate. Real purchasing power will be lower after inflation, and returns may be taxed depending on the account and jurisdiction.
Can I model monthly contributions?
This version projects a single lump sum. For regular deposits, you'd add each contribution's own growth — a feature not included here.