What is the 1RM
The One Rep Max (1RM) is the maximum weight you can lift for a single complete repetition with correct technique. It is the universal reference in weight training programming: workloads are typically expressed as a percentage of 1RM (e.g., 3 sets × 5 reps at 80% of 1RM).
The Epley formula
Testing your actual 1RM is risky without experience or proper warm-up. Predictive formulas allow you to estimate it safely from a submaximal weight. The most widely used is Epley: 1RM = weight × (1 + reps / 30).
Example: if you lift 80 kg for 8 reps, your estimated 1RM is 80 × (1 + 8/30) = 80 × 1.267 = 101 kg. The formula is most accurate with few repetitions (1–10): beyond 12 the error increases significantly.
Other common formulas
- Brzycki: 1RM = weight × 36 / (37 − reps)
- Lander: 1RM = weight × 100 / (101.3 − 2.67123 × reps)
- Mayhew: 1RM = weight × 100 / (52.2 + 41.9 × e^(−0.055 × reps))
How to use 1RM in programming
Once you have estimated your 1RM, structure your training by goal:
- Maximum strength: 85–100% of 1RM, 1–5 reps
- Hypertrophy: 65–85% of 1RM, 6–12 reps
- Muscular endurance: 40–65% of 1RM, 12–20+ reps
Reassess your 1RM every 4–8 weeks as your strength progresses, or recalculate it whenever you can do more reps with the same weight.