One Rep Max Calculator (1RM)
Calculate maximum weight you can lift once. Estimates 1RM from sub-max reps using Epley, Brzycki, Lombardi formulas.
Estimated 1RM
What is 1RM?
One Rep Max (1RM) is the maximum weight you can lift for one complete rep with proper form. Standard for measuring strength in powerlifting, bodybuilding, athletics. Testing actual 1RM is risky (high injury chance) — safer to estimate from 3-10 rep sub-max sets using validated formulas: Epley, Brzycki, Lombardi. Used to: set training percentages, track strength progress, compare across athletes, peaking before competitions.
How to use
- Enter weight lifted — In kg or lbs (consistent units)
- Enter reps performed — Number you did with that weight (1-20)
- View estimated 1RM — Average of 3 formulas
- Use for training plans — Calculate working weights (60%, 80%, 90% of 1RM)
Formula
- Epley: 1RM = weight × (1 + reps/30)
- Brzycki: 1RM = weight / (1.0278 – 0.0278 × reps)
- Lombardi: 1RM = weight × reps^0.1
Most accurate for 1-10 reps. Above 10 reps, formulas overestimate.
Tips
- Estimate from 3-6 reps at near-max for most accuracy
- Don't test true 1RM without spotter and warmup
- Training percentages: 70-80% = hypertrophy, 85-95% = strength
- Periodize: progressive overload increases 1RM over time
- Form > weight — sloppy reps don't count for 1RM
FAQs
How often to test 1RM?
Estimate weekly via training logs. Actually test true 1RM: every 3-6 months at most. Frequent max attempts increase injury risk.
Why three formulas?
Each formula uses different assumptions about strength-endurance relationship. Averaging reduces error of any single formula.
What if I'm a beginner?
Don't worry about 1RM. Focus on form, range of motion, progressive overload. 1RM becomes meaningful after 6-12 months of consistent training.
Different 1RM per exercise?
Yes — bench, squat, deadlift, overhead press all have separate 1RMs. Powerlifting total = sum of squat+bench+deadlift 1RMs.