Compound Interest Calculator

Starting amount ($)

Annual interest rate (%)

Compounding

Years

Regular contribution ($)

Contribution frequency

Contribution timing

Final balance —

Total contributions — paid in

Total interest — earned

Results are an estimate. The rate you enter is applied for the whole term with no fees, tax or withdrawals, and interest is credited on a monthly schedule at the compounding frequency you choose. Real accounts vary — this is not financial advice.

How Compound Interest Works

Interest that earns interest, plus whatever you add along the way.

Set the starting point

Enter your starting amount, the annual interest rate, and how often interest compounds — daily, monthly, quarterly or yearly. More frequent compounding earns a little more.

Add contributions and time

Choose how much you add each month or year and whether it lands at the start or end of the period, then set how many years to run. Every deposit compounds from the day it is added.

See growth vs deposits

The result splits your final balance into what you paid in and what interest added, with a year-by-year table. As a rough check, the Rule of 72 estimates doubling time: 72 ÷ rate. Working out loan repayments instead? Try the Loan Calculator.

Frequently Asked Questions

What is the compound interest formula?

The compound interest formula is A = P(1 + r/n)^(nt), where P is the starting principal, r is the annual interest rate as a decimal, n is how many times a year interest compounds, and t is the number of years. For example, 10,000 at 5% compounded monthly for 10 years is 10,000 × (1 + 0.05/12)^(12×10), which is about 16,470. When you add regular contributions the calculator also sums the growth of each deposit, so the year-by-year table reflects both the principal and everything you paid in.

How does compounding frequency affect returns?

The more often interest compounds, the more you earn, because each block of interest starts earning its own interest sooner. The effect is real but modest: 10,000 at 5% for a year is 500 with annual compounding, about 511.62 with monthly, and about 512.67 with daily. The gap between monthly and daily is only a few dollars, while the gap between annual and monthly is larger. This calculator lets you switch between daily, monthly, quarterly and annual compounding to compare them directly.

How do regular contributions change the total?

Regular contributions usually matter more than the starting amount over a long period, because every deposit compounds from the day it is added. Adding 100 a month to a 10,000 balance at 5% for 10 years pushes the final balance well above what the principal alone would reach, and most of the extra is money you paid in rather than interest. The calculator separates total contributions from total interest so you can see how much of the final figure is growth and how much is your own deposits. To project this kind of growth around an expected annual return — with an inflation-adjusted value — use the Investment Calculator.

What is the Rule of 72?

The Rule of 72 is a quick way to estimate how long an amount takes to double: divide 72 by the annual interest rate. At 6%, money doubles in roughly 72 ÷ 6 = 12 years; at 8%, in about 9 years. It is an approximation that works best for rates between about 5% and 10%, and it assumes interest compounds without withdrawals. Use it for a rough mental check, then use this calculator for the exact figure, since it accounts for your compounding frequency and any contributions.

Compound Interest Calculator

How Compound Interest Works

Set the starting point

Add contributions and time

See growth vs deposits

Frequently Asked Questions

More finance calculators

Related finance calculators

Mortgage Calculator

Loan Calculator

Paycheck Calculator

Salary Calculator

Investment Calculator

Sales Tax Calculator

Currency Converter

Invoice Generator

YouTube Money Calculator

AdSense Revenue Calculator

CPM Calculator

All Calculators