One Rep Max (1RM) Calculator

How It Works

Enter the weight you lifted and the number of reps completed. The calculator applies five established formulas — Epley, Brzycki, Lombardi, Mayhew, and O'Conner — to estimate your one-rep max. It then generates a percentage chart showing target weights for common training zones from 50% to 100% of your estimated max.

Example

If you bench press 80 kg for 5 reps, the Epley formula estimates your 1RM as 80 × (1 + 5/30) ≈ 93 kg. Your 80% training load would be about 75 kg, suitable for sets of 5–8 reps in a strength block.

When to use this calculator

• Use it when starting a new strength program that prescribes percentages of your 1RM.
• Use it after a heavy training set to estimate your current max without attempting a risky single.
• Use it to compare strength across different lifts and track progress over training cycles.

Understanding 1RM and strength training

• Your one-rep max reflects peak force production for a single effort — it is the gold standard for measuring absolute strength.
• Training programs use 1RM percentages to set precise loads for hypertrophy, strength, and power phases.
• Tracking estimated 1RM over time shows strength progression even when you train with submaximal weights.

Formulas explained

• The Epley formula (Weight × (1 + Reps / 30)) is simple and widely used in strength research.
• Brzycki (Weight × 36 / (37 − Reps)) gives similar results but tends slightly lower at higher rep counts.
• Lombardi, Mayhew, and O'Conner provide alternative estimates — comparing all five gives a confidence range rather than a single number.

Safety tips for heavy lifting

• Always warm up thoroughly before working near your max — progressive sets of increasing weight prepare joints and muscles.
• Use a spotter or safety pins/bars when attempting loads above 85% of your estimated 1RM.
• Stop the set if your form breaks down; grinding out reps with poor technique increases injury risk without improving your estimate.

Progressive overload basics

• Add small increments (1–2.5 kg / 2.5–5 lb) when you can complete your target reps with good form across all sets.
• Periodize your training by cycling between higher-rep blocks (60–75% 1RM) and heavier blocks (80–95% 1RM).
• Deload every 4–6 weeks — reducing volume or intensity lets connective tissue recover and prepares you for the next progression cycle.