What is effective annual rate (EAR)?

EAR expresses the annualized return after compounding within the year — higher compounding frequency raises EAR for the same nominal rate.

Does the currency dropdown convert money between countries?

No. It only changes number formatting; the math is unchanged.

Can I add monthly savings to the principal?

Yes — enter an optional monthly contribution to model regular deposits with monthly interest accrual.

Is this compound interest calculator free and private?

Yes. It is free with no signup and runs in your browser without uploading your inputs.

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Compound Interest Calculator

Q: What is compound interest?

Interest earned on both principal and previously credited interest, so growth accelerates over time compared with simple interest.

Model A = P(1 + r/n)^nt, continuous compounding, or add monthly contributions. Compare the effective annual rate (EAR) when compounding frequency changes.

✓ No signup ✓ Instant results ✓ Works offline

Inputs

Currency (display)

Principal

Nominal annual interest rate (%)

Time (years)

Extra months (added to years)

Compounding

Additional contribution per month (optional)

Results

Final amount

Interest earned

EAR (effective annual)

Principal

Interest

Year-by-year balance

Year-by-year compound balance and interest earned
Year	Balance	Interest so far

Ideas behind compounding

Albert Einstein is often quoted as calling compound interest “the eighth wonder of the world” — the quote is widely attributed but not well verified. The underlying idea is sound: when interest earns interest, growth accelerates over long horizons.

Rule of 72: roughly 72 ÷ annual percent rate estimates years to double money at constant compounded growth (handy, not exact).

EAR: The effective annual rate lets you compare nominal rates that compound at different frequencies — more frequent compounding within the year lifts the effective yield slightly.

This page is currency-agnostic — pick a display currency; math is the same. Fees, tax, and inflation are not modeled.

Frequently asked questions

What is compound interest?

Interest on your principal and on interest already added — growth speeds up versus simple interest.

What is EAR?

Effective annual rate: the yearly equivalent after compounding. More compounding within the year → higher EAR for the same nominal rate.

Does currency change the math?

No — only display formatting.

Can I model monthly deposits?

Yes — use the optional monthly contribution field.

Is my data uploaded?

No — calculations run locally in your browser.

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