Simple Interest Calculator
Compute simple interest: SI = P × R × T / 100 — fast, free, private.
See how it works
Watch a quick simulation of this tool in action — no file needed.
How to use Simple Interest Calculator
Follow these steps — everything happens instantly in your browser.
- 1
Step 1. Enter the principal amount you're lending or borrowing.
- 2
Step 2. Enter the annual interest rate as a percentage.
- 3
Step 3. Enter the time period and pick the unit (years, months, or days).
- 4
Step 4. See the simple interest, total amount and a principal-vs-interest breakdown.
Why use this tool
Private by design
All processing happens locally in your browser. Open DevTools → Network and you'll see zero file uploads. Ever.
Instant
No upload wait, no queue, no server round-trip. Results appear the moment you drop a file.
Free & unlimited
No accounts, no watermarks, no daily caps. Use it as many times as you like, forever.
Works everywhere
Desktop, tablet or phone — every tool is responsive and installable as a PWA for offline use.
Frequently asked questions
Everything you might want to know about simple interest calculator.
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