One Rep Max Calculator
Estimates one-rep max (1RM) using the Epley formula: 1RM = weight × (1 + reps/30). The 1RM is the maximum weight you can...
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How It Works
Estimates one-rep max (1RM) using the Epley formula: 1RM = weight × (1 + reps/30). The 1RM is the maximum weight you can lift for a single repetition with proper form.
Quick Reference
100kg × 5 reps
100×(1+5/30)
1RM≈117kg
80kg × 8 reps
80×(1+8/30)
1RM≈101kg
70% of 1RM
Hypertrophy zone
Sets of 8-12 reps
Tips & Shortcuts
Use 1RM to set training weights: 70-80% for hypertrophy, 85-95% for strength.
Do not actually attempt a true 1RM without a spotter and proper warmup.
The Epley formula is most accurate for 2-12 reps. Beyond 12 reps, accuracy decreases.
Common Mistakes
Attempting 1RM without proper warmup and preparation
1RM testing requires specific warmup protocol. Prefer the calculated estimate for daily training.
Using 1RM calculated from high rep sets (15+)
Epley formula loses accuracy above 12 reps. Use sets of 3-8 for best estimates.
Frequently Asked Questions
Most accurate for 1–10 reps. Beyond 10 reps, accuracy drops because endurance plays a larger role. Use 3–6 rep sets for the best 1RM estimates.
Epley formula: 1RM = weight × (1 + reps/30). The most widely used estimate. It slightly overestimates, especially at higher rep ranges.
85–95% for strength (1–5 reps), 67–85% for hypertrophy (6–12 reps), 50–67% for muscular endurance (15+ reps).
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