One Rep Max Calculator (1RM)
Estimate your maximum strength for any lift using three validated scientific formulas. Includes full training percentage table.
Best within 1–10 reps for accuracy.
What Is a One Rep Max (1RM) and Why Should You Know Yours?
A one repetition maximum (1RM) is the heaviest weight you can successfully lift for exactly one repetition with proper technique for a given exercise. It is the gold standard measure of maximal strength in resistance training and is used by coaches, athletes, and recreational gym-goers worldwide to design structured, progressive training programmes.
Knowing your 1RM enables percentage-based training — a method endorsed by the National Strength and Conditioning Association (NSCA) and used in nearly every evidence-based strength and hypertrophy programme. Rather than choosing weights arbitrarily, you can prescribe loads as a percentage of your maximum, ensuring the training stimulus is appropriate for your specific goal.
The Three 1RM Prediction Formulas: Explained
Multiple equations have been developed to predict 1RM from submaximal lifts. Our calculator uses three validated formulas and presents both individual and averaged results:
| Formula | Equation | Best Used For |
|---|---|---|
| Epley (1985) | 1RM = Weight × (1 + Reps/30) | General use, most widely cited |
| Brzycki (1993) | 1RM = Weight × (36 ÷ (37 − Reps)) | Most accurate for low reps (≤10) |
| Lombardi (1989) | 1RM = Weight × Reps^0.10 | Good for slightly higher rep ranges |
Research by LeSuer et al. (1997) in the Journal of Strength and Conditioning Research compared seven 1RM prediction equations on bench press, squat, and deadlift and found that formulas performed best within 1–10 repetitions. For highest accuracy, enter a set performed close to failure in the 3–8 rep range.
Percentage-Based Training: How to Use Your 1RM
Once you have your estimated 1RM, you can prescribe training loads scientifically:
- 90–100% 1RM (1–3 reps): Maximal strength development. Used in powerlifting-style programming and peaking phases.
- 80–90% 1RM (3–6 reps): Strength and power development. Heavy compound movements.
- 67–80% 1RM (6–12 reps): The classic hypertrophy range. Optimal for muscle size increases.
- 50–67% 1RM (12–20 reps): Muscular endurance and additional hypertrophy at higher volumes.
Frequently Asked Questions
References
- LeSuer DA et al. The accuracy of prediction equations for estimating 1-RM performance in the bench press. J Strength Cond Res. 1997;11(4):211-213.
- Schoenfeld BJ et al. Strength and Hypertrophy Adaptations Between Low vs High-Load Resistance Training. J Strength Cond Res. 2017;31(12):3508-3523.
- NSCA. Essentials of Strength Training and Conditioning. 4th ed. Haff GG, Triplett NT, eds. Human Kinetics, 2016.
- Brzycki M. Strength testing—Predicting a one-rep max. JOPERD. 1993;64(1):88-90.