One Rep Max (1RM) Calculator
Enter the weight you lifted and how many reps you completed. We'll calculate your estimated one rep max and show your full percentage training table.
What is a one rep max?
Your one rep max (1RM) is the maximum amount of weight you can lift for exactly one repetition with proper form. It is the primary measure of absolute strength in powerlifting, weightlifting, and general strength training.
Most lifters never actually attempt a true 1RM in training — it is highly taxing on the nervous system and carries injury risk. Instead, they use a submaximal test: lift a challenging weight for several reps, then use a formula to estimate the 1RM.
How the Epley formula works
This calculator uses the Epley formula, the most widely validated 1RM estimation equation:
For example, if you bench pressed 80 kg for 8 reps:
The formula is most accurate for sets of 1–10 reps. Beyond 10 reps, muscular endurance plays a larger role than raw strength, which reduces accuracy.
How to use your 1RM for training
The percentage table above is the key output. Most strength programs prescribe loads as a percentage of 1RM:
- 50–60% — warm-up, technique work, high-rep conditioning
- 65–75% — hypertrophy (muscle building), 8–15 reps
- 80–85% — strength-hypertrophy crossover, 4–8 reps
- 87–93% — strength development, 2–4 reps
- 95–100% — peaking, competition prep, 1–2 reps
Progressive overload works best when you have a known baseline. Recalculate your 1RM every 4–8 weeks to update your training weights. Read our guide on progressive overload for beginners and how many sets per week to build muscle.
Track every PR in GymRPG
GymRPG automatically tracks your personal records across every exercise. When you set a new 1RM — even a calculated one — your character gains stats and you unlock boss battles based on your strength level.
Log your lifts, track PRs, and battle bosses — free on Android.
Frequently asked questions
What is a one rep max (1RM)?
Your one rep max is the maximum weight you can lift for a single repetition with correct form. It is the gold standard measure of strength in powerlifting and strength training.
How accurate is the Epley 1RM formula?
The Epley formula is most accurate when calculated from sets of 1–10 reps. Accuracy decreases above 10 reps because muscular endurance becomes a larger factor than raw strength.
Should I actually attempt my calculated 1RM?
Not without preparation. Use the percentage table to work up gradually — spend several sessions at 85–90% before attempting a true max. Always use a spotter for free-weight movements.
Which exercises can I use this calculator for?
Any barbell or machine compound lift: squat, bench press, deadlift, overhead press, row, leg press. Avoid using it for isolation exercises like curls where form breaks down at high loads.
How often should I retest my 1RM?
Every 4–8 weeks of progressive overload training. Retesting too often is fatiguing and unnecessary — track progress by how your rep maxes at 70–85% increase over time.