See how savings grow · free

Compound Interest Calculator

Last updated: October 2026

See how much a starting amount grows when interest is added to interest. Enter the amount, the yearly rate, the number of years and how often it compounds, and get the final balance and total interest earned.

Monthly, quarterly, yearly, daily
Shows the formula
Runs on your device

Compound interest means you earn interest on your interest. Over a few years the difference is small, but over decades it becomes the biggest part of the balance. Use this calculator to compare rates, time periods and compounding schedules side by side.

How To Use The Compound Interest Calculator

Enter the starting amount, the money you deposit at the beginning.
Enter the yearly interest rate as a percent, for example 4 for 4%.
Enter the number of years. Part years such as 2.5 work too.
Choose how often interest compounds: monthly, quarterly, yearly or daily. Check your account terms if you are not sure.

The Compound Interest Formula

Compound interestA = P × (1 + r/n)^{n × t}A = final amount · P = starting amount · r = yearly rate as a decimal · n = compounds per year · t = years

The interest earned is simply A − P. The calculator shows the formula filled in with your numbers under the result.

Worked Examples

Savings Over Three Years

Problem: You save $5,000 at 4% a year, compounded monthly, for 3 years.
Formula: 5000 × (1 + 0.04/12)^(12 × 3)
Result: $5,636.36, which is $636.36 of interest.

Ten Years At 5%

Problem: $10,000 at 5% a year, compounded monthly, for 10 years.
Result: $16,470.09. Simple interest would give only $15,000, so compounding adds $1,470.09.

How Often Interest Compounds Matters

Here is the same $5,000 at 4% for 3 years with each compounding option. More frequent compounding earns a little more, but the rate and the time matter far more.

Compounds	Times per year	Final amount	Interest earned
Yearly	1	$5,624.32	$624.32
Monthly	12	$5,636.36	$636.36
Daily	365	$5,637.45	$637.45

This calculator assumes a single deposit and a fixed rate. Real accounts may add fees, taxes or rate changes, and regular monthly deposits would grow the balance faster. It is a learning tool, not financial advice.

Compare your own numbers

Change the rate or the years and watch the balance update.

Open the interest calculator

Frequently Asked Questions

What is the difference between simple and compound interest?

Simple interest is paid only on the starting amount. Compound interest is paid on the starting amount plus any interest already added, so the balance grows faster each year.

What is APY?

APY, or annual percentage yield, is the yearly rate after compounding is included. A 4% rate compounded monthly has an APY of about 4.07%.

Does daily compounding make a big difference?

Not much. In the example above, daily compounding earns only $1.09 more than monthly over three years. A higher rate or a longer time has a much bigger effect.

Can I add monthly deposits?

This version handles one starting deposit. To estimate regular saving, run the calculator for each deposit or add the results for each year.

Is this financial advice?

No. The results are estimates for learning and planning. Speak to a qualified adviser before making financial decisions.