How is one-rep max calculated?
Your one-rep max (1RM) is the maximum weight you can lift for a single repetition. Rather than risk a true max attempt, this calculator estimates it from a lighter set using two well-known formulas:
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × 36 ÷ (37 − reps)
How to use the percentage table
Most strength programs prescribe work as a percentage of your 1RM. For example, hypertrophy work often sits around 67–75% (8–12 reps), while strength work uses 85%+ (1–5 reps). The table above converts your 1RM into exact working weights.
How often should I retest?
Every 4–8 weeks. Strength changes gradually, so frequent maxing isn't needed and adds fatigue.
Are these estimates exact?
They're close for low-rep sets but individual. Use them as a starting point and adjust based on how the weight actually feels.