Compound Interest Calculator
Calculate compound interest.
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Your inputs are processed locally in your browser and are not uploaded or stored by us.
Calculate compound interest based on a principal amount, an interest rate, and a compounding frequency. Compound interest accumulates on both the initial principal and the previously added interest.
How to calculate compound interest
- Enter the principal amount.
- Enter the annual interest rate as a percentage (e.g., enter 5 for 5%).
- Enter the number of times the interest compounds per year (e.g., 12 for monthly).
- Enter the time period in years.
- Click "Calculate" to find the total amount and interest earned.
Compound Interest Formula
A = P × (1 + r/n)^(n×t)
Interest = A − P
Where P is the principal, r is the annual percentage converted to decimal, n is compounds per year, and t is time in years. The calculator evaluates the exponentiation of the periodic factor (1 + r/n) to determine the total accumulated amount.
Example calculation (monthly compounding)
Principal1000
Annual rate5%
Compounds per year12
Time1 year
A = 1000 × (1 + 0.05/12)^(12 × 1)
Result: Total Amount ≈ 1051.16, Interest ≈ 51.16
Notes
- Compounds per year must be a positive integer.
- Years = 0 results in total = principal and interest = 0.
- Negative interest rates are allowed as long as the real-domain condition 1 + r/n >= 0 is met. If this periodic factor becomes negative, the calculation is rejected to avoid non-real complex numbers.
- This calculator does not model fees, taxes, continuous compounding, additional deposits, or withdrawals.
- Compound-interest results use JavaScript floating-point arithmetic and may be approximate.
- Your calculator inputs are processed locally in your browser and are not uploaded or stored by us.