Business Tools

Free Compound Interest Calculator

Compound interest is the effect of earning (or paying) interest on top of previously accrued interest. Over long periods it dwarfs simple interest — this calculator quantifies both the maturity value and the year-by-year growth path.

Results

Principal$10,000.00
Compound interest$12,196.40
Maturity value$22,196.40

Growth over 10 years

$10,000.00$22,196.40

Disclaimer: This calculator provides estimates only and does not constitute financial advice. Actual loan terms may vary by lender.

What the Compound Interest Calculator does

Compound interest is interest calculated on both the original principal and the interest already accrued in prior periods, causing balances to grow faster than simple interest over time. It applies equally to savings that grow and to debt that grows.

Methodology and formula

A = P x (1 + R/n)^(n x t), where P = principal, R = annual interest rate (decimal), n = compounding periods per year, t = time in years; Compound Interest = A - P.

Worked example

Inputs
Principal 10,000; annual rate 8%; compounded monthly; time 5 years.
Result
A = 10,000 x (1 + 0.08/12)^60 = about 14,898; compound interest about 4,898.

Compared with simple interest at the same rate (4,000 over 5 years), monthly compounding adds nearly 900 extra — the gap widens sharply the longer the money is left to grow.

When to use this tool

Use this for savings, fixed deposits or any debt that compounds, such as credit-card balances. Use the Simple Interest Calculator for flat-rate short-term financing, or the Loan ROI Calculator to weigh a loan's compounding cost against an investment's return.

About the Compound Interest Calculator

The formula

A = P × (1 + R/n)^(nt), where P is principal, R is annual rate (decimal), n is compounding frequency per year (1 annual, 4 quarterly, 12 monthly) and t is time in years. Compound Interest = A − P.

Why compounding frequency matters

The more frequent the compounding, the higher the effective yield. $10,000 at 10% for 10 years is $25,937 annually compounded, $26,850 quarterly, $27,070 monthly. Small on year one, meaningful by year ten.

The rule of 72

A quick sanity check: money doubles in roughly 72 ÷ interest rate years. At 8% compound, money doubles in about 9 years. Use this to spot-check the calculator's output.

Frequently asked questions

How is compound interest different from simple interest?

Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus previously accrued interest, so the balance grows faster over time.

Which compounding frequency should I choose?

Use the frequency your bank or lender specifies. Fixed deposits are typically quarterly; savings accounts are often monthly; some bonds are annual.

Does compounding work for me or against me?

Both. On investments and deposits, compounding grows your money. On loans and credit-card balances, it grows your debt just as fast — which is why credit-card debt is so dangerous.

Related Loan Tools

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See whether a loan-funded investment actually pays off. Enter the total loan cost and expected return to get a plain-English net ROI.

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