Compound Interest Calculator

Project compound growth with whole-month durations and optional end-of-month contributions.

Fixed-rate growth estimate

The annual rate is treated as a nominal rate with your selected compounding frequency. Contributions are added at the end of every month. Enter every amount in one currency; results use those same entered currency units and no currency conversion is performed.

Initial investment (currency units)

May be zero when the monthly contribution is greater than zero.

End-of-month contribution (same currency units)

Nominal annual interest rate (%)

Time period (years)

Use a whole number of months, up to 100 years (1,200 months); 0.5 years is 6 months.

Nominal compounding frequency

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Continue with related pages to compare results and improve decision making.

View Finance Category Read the Compound Interest Calculator Guide

What This Compound Interest Projection Includes

This compound interest calculator projects a hypothetical future value from an initial amount, nominal annual return, compounding frequency, whole-month duration, and optional end-of-month contributions. It does not model fees, tax, inflation, or variable returns.

Compound Growth and Contribution Formula

The core formula used by this compound interest calculator is: Principal growth follows A = P(1 + r/n)^(nt). Optional contributions are deposited at the end of each month and grow using the monthly rate equivalent to the selected compounding frequency.

The equation applies returns to principal and accumulated gains. The calculator converts the selected nominal compounding convention to an equivalent monthly factor so it can model whole-month durations and monthly contributions consistently.

An initial 10,000 earning a nominal 8% compounded monthly for one year, with 500 added at the end of each month, projects to about 17,054.96: 16,000 contributed and about 1,054.96 of growth.

Compound Interest Example

One year with monthly contributions

Start with 10,000, use an 8% nominal annual rate compounded monthly for 12 months, and add 500 at the end of each month.

Projected ending value: about 17,054.96; total contributed: 16,000; projected growth: about 1,054.96.

This is a fixed-rate projection before fees, tax, inflation, and market variation.

Build a Compound Growth Scenario

Enter initial investment amount.
Set expected annual return and compounding period.
Add an optional contribution made at the end of every month.
Review projected ending value, total contributions, and projected growth.

What the Projection Helps You Compare

Separate money contributed from projected compound growth.
Compare the same starting balance under different rates and compounding frequencies.
See how consistent end-of-month contributions affect a projection.
Check the assumptions behind a hypothetical growth figure.

Related Finance Calculators

Try the Loan Calculator for a related calculation.
Try the Mortgage Calculator for a related calculation.
Read the Compound Interest Calculator Guide for examples and assumptions.
Browse the Finance Calculators page for more tools.

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Frequently Asked Questions

What is compound interest?

Compound interest is interest earned on both your principal and previously earned interest, creating exponential growth over time.

Does compounding frequency matter?

Yes. More frequent compounding can increase final value because gains are reinvested sooner.

Can I use this for SIP-style contributions?

You can model equal end-of-month contributions as a projection. Actual investment results can differ because returns vary and products may include fees, tax, or different contribution timing.