Compound Interest Calculator — Free Online Tool
See how your money grows with daily, monthly, or yearly compounding. · No signup · Works on mobile
100% private: your data is processed in your browser. Nothing is uploaded to our servers.
How to use the compound interest calculator
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Enter your starting principal and optional monthly contribution.
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Set the annual interest rate, investment duration, and compounding frequency (daily, monthly, quarterly, yearly).
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3
View the final balance, total interest earned, and the year-by-year growth table.
What does this tool do?
This free compound interest calculator shows exactly how an investment grows over time when interest earns interest. Enter your principal, rate, time period, and compounding frequency to instantly see the final amount, total interest earned, and a year-by-year growth breakdown.
How does the compound interest calculator work?
It applies the compound interest formula A = P(1 + r/n)^(n×t), where P is principal, r the annual rate, n the compounding periods per year, and t the years. Optional monthly contributions are compounded from the month they are added.
Frequently Asked Questions
What is the difference between simple and compound interest?
Simple interest is calculated only on the original principal, while compound interest is calculated on the principal plus all previously earned interest. Over 20 years at 8%, $10,000 earns $16,000 with simple interest but about $36,610 with annual compounding — more than double.
How often should interest compound for best returns?
More frequent compounding yields more, but with diminishing returns. $10,000 at 8% for 10 years grows to $21,589 with annual compounding, $22,196 with monthly, and $22,253 with daily — the jump from annual to monthly matters far more than monthly to daily.
Is the compound interest calculator really free?
Yes — 100% free with no hidden charges, trial limits, or premium tiers for core features. You don't need to create an account or enter an email address. The site is supported by non-intrusive display ads, which keeps every tool free for everyone.
Is my data private when using the compound interest calculator?
Completely. The compound interest calculator runs entirely in your browser using JavaScript — nothing you type or upload is sent to our servers. When you close the tab, your data is gone. This makes it safe for confidential documents, financial figures, and personal information.
Does the compound interest calculator work on mobile phones?
Yes. The compound interest calculator is built mobile-first and works on any phone or tablet with a modern browser — iPhone (Safari), Android (Chrome), and everything in between. The layout adapts to small screens, so buttons and inputs stay easy to tap on a 375px-wide display.
Do I need to install anything to use the compound interest calculator?
No. The compound interest calculator works directly in your web browser — no downloads, no extensions, no signup. Just open the page, use the tool, and get your result instantly. It works on Windows, macOS, Linux, ChromeOS, iOS, and Android.