Compound Interest Calculator

Estimate how an investment, savings balance, or loan-style balance can grow when interest earns interest. Enter a starting amount, annual rate, compounding frequency, term, and optional regular contributions to see the future value, total interest, and year-by-year breakdown.

Core formula
A = P x (1 + r / n)^(n x t)

Compound Interest Calculator

Instant
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Starting savings, investment principal, or current balance.
%
$
Future value
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Total interest
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Total contributions
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Effective annual rate
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Formula used
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Growth Breakdown

See how much of the final balance comes from your starting amount, new money, and compound interest.

Starting amount
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The original principal before interest or new contributions.

New contributions
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Total regular deposits added during the selected term.

Interest earned
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Growth created by compounding before tax, fees, or inflation.

Compound Interest Calculator Examples

Load a common savings or investment scenario to compare monthly compounding, daily compounding, lump sums, and recurring deposits.

$10,000 plus $250 monthly at 6%

A practical savings plan that shows both interest growth and the effect of regular monthly contributions.

$5,000 at 4.5% compounded daily

Useful when comparing savings accounts or certificates that advertise daily compound interest.

$25,000 invested for 20 years

A long-term lump sum example that makes the compounding curve easy to see in the yearly table.

$50 weekly contribution plan

Shows how smaller frequent deposits can build value when contributions are made at the beginning of each period.

Year-by-Year Compound Interest Table

The table is generated from the same inputs as the calculator so you can audit the compounding path instead of only seeing the final answer.

Year Starting balance Contributions Interest earned Ending balance

Compound Interest Formula

The basic compound interest formula works for lump sums. Regular contributions are modeled period by period so deposits, interest, and timing stay transparent.

Lump sum compound interest

A = P x (1 + r / n)^(n x t)

A is future value, P is principal, r is the annual rate as a decimal, n is compounding periods per year, and t is years.

Interest earned

Interest = Future value - Principal - Contributions

This separates true compound growth from money you added manually.

Effective annual rate

EAR = (1 + r / n)^n - 1

Daily or monthly compounding can produce a slightly higher effective rate than the quoted annual rate.

Excel-style formula

Future value = FV(rate / n, n x years, -payment, -principal)

Spreadsheet FV formulas use signed cash flows, so payments and principal are often entered as negative values.

How to Use the Compound Interest Calculator

Use the calculator as a planning estimate. For investments, real returns can vary; for savings accounts, taxes and fees can change the final value.

1

Enter the starting amount

Use your current balance, deposit, investment principal, or the amount you want to grow.

2

Set rate and time

Enter the annual interest rate as a percent and the number of years you want to project.

3

Choose compounding

Select annual, monthly, weekly, or daily compounding to match the account or scenario you are comparing.

4

Add contributions

Optional regular deposits can be monthly, biweekly, weekly, or yearly, and can be applied at the beginning or end of each period.

Compound Interest Edge Cases

Small assumptions can change the projection, especially over long time periods.

Daily vs monthly compounding

Daily compounding usually produces a slightly higher balance than monthly compounding at the same quoted annual rate, but the difference may be small for short terms.

Contributions are not returns

The calculator separates new deposits from interest earned so you can see whether growth comes from compounding or from additional savings.

Nominal vs effective rate

The quoted annual rate is nominal. The effective annual rate includes how often interest compounds during the year.

Taxes, fees, and inflation

This calculator does not subtract tax, investment fees, account fees, or inflation. Use the result as a gross estimate.

Compound Interest Calculator FAQ

Answers to common questions about compounding frequency, formulas, and spreadsheet-style calculations.

Compound interest is interest earned on both the original principal and previously earned interest. Over time, that creates a growth curve instead of a simple straight-line increase.

Use A = P x (1 + r / n)^(n x t). Convert the annual rate to a decimal, divide it by the number of compounding periods per year, raise it to total periods, and multiply by the principal.

Daily compounding gives interest more chances to earn interest, so it usually produces a slightly higher future value than monthly compounding at the same nominal annual rate.

Yes. Enter a regular contribution and choose monthly, biweekly, weekly, or yearly timing. The calculator models each period and separates contributions from interest earned.

Spreadsheet finance functions treat cash paid out and cash received as opposite signs. Entering principal and payments as negative values often returns a positive future value.

Compare compound growth before you commit

Change the rate, compounding frequency, and regular contribution to see which assumption actually moves the final balance.

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