How the Epley and Brzycki 1RM formulas work
Testing a true single-rep maximum requires heavy neural arousal, spotters, and extra recovery time. Submaximal prediction equations let you estimate maximal strength from a working set you already perform in training [1] [2].
Epley Formula (1985):
1RM = Weight × (1 + Reps / 30)
Brzycki Formula (1993):
1RM = Weight × 36 / (37 - Reps)
At 1 repetition, both equations return the exact weight lifted. Between 2 and 8 repetitions, Epley and Brzycki sit within a few percent of each other; at 9 to 10 repetitions, averaging both helps avoid overestimating working loads [3].
How to apply your 1RM percentages to a workout plan
- Strength and neural efficiency (85% to 92% of 1RM, 2 to 5 reps): Used on primary barbell squats, bench presses, and deadlifts with 2 to 4 minutes of rest between sets.
- Hypertrophy compound work (70% to 82% of 1RM, 6 to 10 reps): Balances mechanical tension and manageable joint fatigue for multi-joint lifts in our weekly workout plan generator and equipment-filtered routines.
- Volume and unilateral/accessory lifts (60% to 72% of 1RM, 10 to 15 reps): Useful for split squats, rows, and isolation movements where stability or joint comfort matters more than peak bar load. See the Exercise Substitution Library when converting loads across equipment.
Safety and estimation limits
Educational tool for healthy adults. Prediction accuracy drops above 10 repetitions because local muscular endurance and cardiovascular fatigue influence the set. Do not use a 1RM formula to pick a maximal single on single-joint isolation movements (such as lateral raises or skull crushers) or when returning from an injury.