One Rep Max Calculator
Calculate your maximum single-rep strength (1RM) using the clinical Epley and Brzycki powerlifting formulas.
About the One Rep Max (1RM)
Your one-repetition maximum is the maximum amount of weight you can move through a full range of motion for a single repetition with proper biomechanical technique.
Formulas
- Epley Formula: 1RM = Weight × (1 + Reps / 30)
- Brzycki Formula: 1RM = Weight × (36 / (37 - Reps))
Worked Example
If you bench press 100 kg for 5 repetitions:
- Epley: 100 × (1 + 5/30) = 116.7 kg
- Brzycki: 100 × (36 / (37 - 5)) = 112.5 kg
- Consensus Average: ~115 kg
Frequently Asked Questions
Why calculate 1RM instead of testing it directly?
Testing true 1RM on compound lifts carries significant joint and soft-tissue injury risk. Submaximal calculations give accurate load baselines safely.
How accurate is the formula past 10 repetitions?
Accuracy degrades significantly beyond 10 to 12 reps because cardiovascular endurance and lactic acid buffering begin confounding pure muscle force production.
How should I use percentage training?
Powerlifting and hypertrophy programs prescribe intensities based on 1RM (e.g., hypertrophy at 70-80% 1RM, absolute strength at 85-95% 1RM).
Does 1RM transfer across different exercises?
No. 1RM is movement-specific due to biomechanical leverages, muscle recruitment patterns, and joint moment arms.
Calculate in three steps
- 1Enter your valuesUse the fields above and check the units shown beside each input.
- 2Run the calculationSelect Calculate to refresh the result with your latest values.
- 3Review or shareCompare the result, reset the form, print it, or share this page.