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Compound Interest Calculator

Calculate compound interest with regular deposits, multiple compounding frequencies, and timeline breakdowns.

Runs in your browser. Nothing you add is uploaded.

What the Compound Interest Calculator does

Compound interest is interest calculated on the initial principal and also on the accumulated interest of previous periods. Often referred to as the eighth wonder of the world, compound interest accelerates savings dramatically over long timeframes. This tool calculates future values across daily, monthly, quarterly, and annual compounding schedules with optional monthly additions.

How to calculate compound interest

  1. Enter your starting principal deposit amount.
  2. Specify any additional regular monthly contributions you plan to make.
  3. Input the annual interest rate (APY/APR) and total investment time horizon in years.
  4. Select your account compounding frequency (e.g. daily, monthly, or annually) to compute the final maturity value.

The Compound Interest Calculator runs entirely in your browser — nothing you enter is uploaded, stored, or logged.

How it works

Compound Interest Formula

A = P(1 + r/n)^(nt)

Where P is principal, r is annual interest rate, n is compounding frequency per year, and t is time in years.

Example: 50,000 at 8% compounded monthly for 5 years yields ~74,492.

When to use it

High-yield savings accounts & Certificates of Deposit (CDs)

Calculate the exact interest payout from banks compounding interest monthly or daily.

Long-term investment portfolio compounding

Model how reinvested dividend payments and asset growth accumulate over multiple decades.

Loan and mortgage debt growth

Understand how compounding interest affects unpaid loan balances or credit card debts over time.

Good to know

  • Daily compounding yields slightly higher returns than annual compounding at the same nominal interest rate.
  • The Rule of 72 provides a quick mental estimate: divide 72 by your interest rate to estimate how many years it takes to double your money.
  • Consistent regular monthly contributions can outweigh the starting principal in long-term wealth building.

Guides that use this tool

Frequently asked questions

What is the difference between simple and compound interest?

Simple interest calculates returns only on the initial principal, while compound interest adds accumulated interest back to the principal for exponential growth.

What is Effective Annual Rate (EAR)?

Effective Annual Rate is the true annual interest rate earned after accounting for the compounding frequency, which is higher than the nominal stated interest rate when compounding occurs more than once per year.

How does compounding frequency impact returns?

More frequent compounding (e.g., daily vs annually) means accrued interest starts earning interest sooner, yielding a higher future value.

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