---
title: "Compound Interest Calculator with Monthly Contributions"
description: "Calculate savings growth with monthly contributions, daily or monthly compounding, and APY/AER input. Compare deposits and download your growth schedule."
url: "https://worldcalculators.org/calculators/compound-interest/"
canonical: "https://worldcalculators.org/calculators/compound-interest/"
---

# Compound interest calculator.

Calculate savings growth with monthly contributions, daily or monthly compounding, and APY/AER input. Compare deposits and download your growth schedule.

## Quick answer

At an illustrative 5% nominal annual rate compounded monthly for 10 years, a $10,000 initial deposit plus $100 at the end of each month grows to $31,998.32 . That is $22,000.00 deposited and $9,998.32 projected interest , before tax, fees and inflation.

## Small habits. Visible progress.

Explore an illustrative return, not a guaranteed outcome.
Labels only; no exchange-rate conversion.

## The compound interest formula

Without additional deposits, the compound interest formula is A = P × (1 + r/n)^(n × t) . P is your starting principal, r is the nominal annual rate as a decimal, n is the number of compounding periods per year and t is time in years. The result A includes your principal; subtract P to find interest earned.
For $10,000 at 5% compounded monthly over 10 years, the balance is $16,470.09 . A simple-interest calculation for the same principal, rate and duration would give $15,000. The difference comes from earning interest on previously accumulated interest.

## Adding monthly contributions correctly

For end-of-month contributions, use the equivalent monthly rate i = (1 + r/n)^(n/12) − 1 and the number of months m:
C is one monthly contribution. For start-of-month contributions, multiply the contribution portion by (1+i). At zero interest, use P + C × m . This calculator simulates the same process month by month, making the deposit count explicit in the result.

## Nominal interest rate versus APY and AER

A nominal savings rate is the rate before accounting for compounding. APY and AER are effective annual yields. For a nominal decimal rate r compounded n times a year, the effective annual yield is (1 + r/n)^n − 1 . Enter an advertised APY or AER using the effective-yield option; applying another round of compounding to it would overstate growth.
Be careful with the term APR. In borrowing, APR can include fees as well as interest. A loan APR is not automatically the nominal deposit rate required by a savings formula. Compare like-for-like disclosures and check whether a quoted savings rate changes after an introductory period.

## Daily, monthly, quarterly or annual compounding?

At the same positive nominal rate, more frequent compounding increases the effective yield. These examples use $10,000 at a 5% nominal rate for 10 years, with no further deposits.

## Turn the result into a useful comparison

Start with a contribution you can sustain and compare it with zero deposits and an additional 100 per month. Then change the return assumption to see how sensitive your plan is. A future investment return is uncertain, so one smooth growth curve should not be read as a forecast of market performance.
The balance is in today's selected currency units, without an inflation adjustment. If purchasing power is your question, continue to the inflation calculator . If you know the amount you need and want to work back to a savings plan, try the savings calculator . Download the monthly schedule to keep a record of the assumptions behind your scenario.

## Sources & Methodology

The interactive calculator and worked examples share one tested monthly simulation. Full precision is retained until display. Effective annual yields are converted to equivalent monthly growth without double-compounding.
Standards and figures reviewed 9 September 2026.

Source: https://worldcalculators.org/calculators/compound-interest/
Markdown mirror of the HTML page. Prefer this URL for RAG; the interactive calculator still lives on the HTML page.