Annual Compound Interest Calculator
Calculate growth when interest compounds once per year.
What the Annual Compound Interest Calculator does
Annual compounding is the simplest case and the baseline for comparing investments. The nominal rate and the effective rate are identical, which makes it the cleanest way to reason about long-run growth.
Formula
A = P × (1 + r)ᵗ
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Initial amount | selected currency | Yes | Accepts more than 0. |
| Annual interest rate | % | Yes | — |
| Number of years | years | Yes | Accepts more than 0, up to 100. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Currency.
- Enter Initial amount, Annual interest rate and Number of years.
- Select Calculate.
Worked example
$15,000 at 9% compounded annually for 10 years.
- Amount
- 15000
- Rate
- 9
- Years
- 10
15,000 × 1.09¹⁰ = $35,510 — the money multiplies by 2.37×.
Reading the result
- With annual compounding the nominal and effective rates are identical, which makes this the cleanest baseline for comparing growth.
- The balance accelerates because each year earns on the previous year’s interest as well as the principal — the gap widens most in the final years, not the first.
Assumptions and limitations
- A single constant rate applied every year, with no tax, fees or withdrawals. No real investment behaves this way; the figure shows what a steady rate would produce.
Common mistakes
- Entering the rate as a decimal when a percentage is expected, so 0.07 is read as 0.07% rather than 7%.
- Reading a long projection as spending power. At 3% inflation, money halves in real terms roughly every 24 years.
Frequently asked questions
Why does the balance accelerate?
Each year the interest is calculated on a larger balance, so the amount added grows every year even though the rate never changes.