How to Calculate One Rep Max
What is One Rep Max?
The one-repetition maximum (1RM) is the maximum weight you can lift for a single repetition of an exercise with good form. It is the gold standard for measuring strength and is used to calculate training percentages. Because testing true 1RM carries injury risk, estimation formulas from submaximal efforts are commonly used.
Formula
Step-by-Step Guide
- 1Epley (1985): 1RM = weight × (1 + reps/30)
- 2Brzycki (1993): 1RM = weight × 36 / (37 − reps)
- 3Both formulas are most accurate for 3–10 reps; less accurate above 12
- 4Training percentages are calculated as % of 1RM for different adaptations
Worked Examples
Frequently Asked Questions
What is One Rep Max?
The one-repetition maximum (1RM) is the maximum weight you can lift for a single repetition of an exercise with good form. It is the gold standard for measuring strength and is used to calculate training percentages
How accurate is the One Rep Max calculator?
The calculator uses the standard published formula for one rep max. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.
What units does the One Rep Max calculator use?
This calculator works with inches, percentages. You can enter values in the units shown — the calculator handles all conversions internally.
What formula does the One Rep Max calculator use?
The core formula is: Epley (1985): 1RM = weight × (1 + reps/30). Each step in the calculation is shown so you can verify the result manually.
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