What Is a One-Rep Max (1RM)?
A one-rep max (1RM) is the heaviest weight a person can lift once with correct form in a given exercise. Because testing it directly is demanding, it is often estimated from a lighter set taken close to failure using formulas such as Epley: 1RM = weight × (1 + reps ÷ 30).
Common Formulas
Epley: weight × (1 + reps ÷ 30). Brzycki: weight × 36 ÷ (37 − reps). Estimates are most reliable for sets of about ten reps or fewer.
How 1RM Is Used
Training programs often prescribe loads as a percentage of 1RM, for example 75% of 1RM for sets of about ten repetitions.
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🔗 Related Terms
More Health & Fitness Terms
- Basal Metabolic Rate (BMR)
- Body Composition
- Body Mass Index (BMI)
- Calorie
- Calorie Deficit
- Circadian Rhythm
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Last updated: September 27, 2026. This definition is for general educational purposes only. It is not financial, investment, tax, legal, or medical advice, and it does not recommend any product or course of action. For decisions about your own situation, consult a qualified professional.