1RM Calculator
Estimate your one-rep max using 7 formulas + training percentages.
See how it works
Watch a quick simulation of this tool in action — no file needed.
How to use 1RM Calculator
Follow these steps — everything happens instantly in your browser.
- 1
Step 1. Enter the weight you lifted in kilograms.
- 2
Step 2. Enter the reps performed (1–15).
- 3
Step 3. Pick a formula (or compare across all seven).
- 4
Step 4. Read your estimated 1RM and the training percentages.
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 1rm calculator.