Compound Interest Calculator

Common Ways People Use Compound Interest Calculator

This Compound Interest Calculator shows exactly how your savings or investments grow over time, factoring in your principal, interest rate, compounding…

• Estimating how a savings account will grow over several years.
• Comparing two investment offers with different compounding frequencies.
• Planning how much to set aside monthly to hit a future savings goal.
• Understanding how interest compounds differently than simple interest over time.

Because Compound Interest Calculator runs entirely in your browser, none of the files or numbers you enter are uploaded anywhere — everything is processed locally on your own device and cleared as soon as you close the tab.

How Compound Interest Works

The Basic Idea

Compound interest means you earn interest not just on your original amount, but also on the interest that's already been added — so your money grows faster over time.

Compounding Frequency

Interest can compound annually, monthly, or even daily. The more frequently it compounds, the faster your balance grows, even at the same annual rate.

Time Is the Biggest Factor

Because compounding builds on itself, the longer your money stays invested, the bigger the difference between compound and simple interest becomes.

Compound Interest and Debt

The same principle works against you with debt — unpaid interest on a loan or credit card can compound and grow the amount you owe.

More Things to Know

Simple Interest vs. Compound Interest

Simple interest is calculated only on the original principal each period. Compound interest is calculated on the principal plus any interest already earned, which is why it grows faster over time.

The Rule of 72

A quick way to estimate how long it takes an investment to double: divide 72 by the annual interest rate. At 6% interest, money roughly doubles in 12 years.

Regular Contributions

Adding regular deposits on top of compound interest accelerates growth significantly compared to a single lump sum left untouched.

Inflation's Effect

Compound growth looks impressive in raw numbers, but it's worth comparing your interest rate to inflation to understand your real, inflation-adjusted returns.

Additional Context

Compound Interest in Retirement Planning

Long-term retirement accounts benefit enormously from compound growth, which is why financial advisors consistently emphasize starting to save early, even with small amounts.

Understanding APY vs. APR

Annual Percentage Yield (APY) accounts for compounding, while Annual Percentage Rate (APR) typically does not — this distinction matters when comparing savings accounts or loans.