One Rep Max Calculator
Estimate your one-rep max from a weight and reps, in kg or lb, with a full percentage training table. Free and private in your browser.
Report a problemThis is an estimate from a formula, not medical advice. Real maxes vary by exercise, technique and the day — always warm up, use a spotter and lift within your limits.
How to use
- Pick kilograms or pounds, then type the weight you lifted and how many clean reps you got with it.
- Your estimated one-rep max updates live as you type — there is nothing to submit.
- Use the percentage table to plan training loads: each row shows a percentage of your max, the weight that works out to, and the rough number of reps you can expect at that intensity.
FAQ
How is one-rep max calculated?
This tool uses the Epley formula, one of the most widely used estimates: one-rep max equals the weight multiplied by (1 + reps ÷ 30). For a single rep the weight you lifted is already your max, so it is returned as-is. For example, 100 kg for 5 reps gives roughly 117 kg. The estimate is most reliable for sets of about 2 to 10 reps; very high-rep sets drift further from your true max because fatigue and pacing play a bigger role than raw strength.
Is anything I type sent to a server?
No. Your weight and reps are used for plain arithmetic right in your browser — nothing is uploaded or stored. The calculator works offline and keeps your numbers private.
Should I actually try to lift my estimated max?
Treat the number as a planning guide, not a target to chase. This is an estimate from a formula, not medical or coaching advice. Maxing out is demanding and carries injury risk, so build up gradually, warm up thoroughly, use proper form and a spotter, and stop if anything feels wrong. If you are new to lifting or returning from injury, check with a qualified coach or health professional first.