Compound Interest Calculator

About Compound Interest

Compound interest reinvests earned interest so future periods earn on a larger base. Long horizons dramatically amplify growth compared with simple interest.

Real investments face volatility, taxes, fees, and inflation not fully modeled in basic calculators.

Educational projections only—not financial advice. Currency label is display-only.

How to use this tool

Provide principal, annual rate, compounding frequency, time period, and optional regular contributions. Calculate future value and interest earned.

Formula & methodology

This compound interest calculator applies the standard relationship below. Intermediate values are kept at full precision; only the displayed result is rounded.

FV = P(1 + r/n)^(nt) + PMT x [((1 + r/n)^(nt) - 1) / (r/n)] (annuity forms vary)

Worked example

Invest 10,000 at 8% per year, compounded monthly, for 10 years: A = 10,000 × (1 + 0.08/12)^(12 × 10) = 10,000 × 2.21964 ≈ 22,196.40. Interest earned is about 12,196.40 — compared with 8,000 under simple interest, the extra 4,196 is the effect of compounding.

Tips for accurate results

• Higher compounding frequency slightly increases effective yield at same nominal rate.
• Start early; time in market matters in compound models.
• Subtract estimated inflation mentally for real purchasing power.
• Do not treat projected FV as guaranteed returns.

Frequently asked questions

Sources & references

The factors and formulas used by this tool follow these references:

• Consumer Financial Protection Bureau — consumer tools and explainers
• U.S. SEC Investor.gov — Compound Interest Calculator and definitions

Finance results are estimates based on the figures you enter and standard formulas. They are not tax, investment, or lending advice; actual bank terms, fees, and tax rules may differ.

Last reviewed: September 2026. Found an error? Tell us and we will correct it.