Strength Training
1RM Calculator — One Rep Max Estimator
Estimate your one-rep maximum (1RM) using three industry-standard formulas.
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1RM Formulas Explained
Our calculator uses three validated formulas and averages them for the most reliable estimate.
Epley Formula (1985)
1RM = weight × (1 + reps / 30)
Brzycki Formula (1993)
1RM = weight × (36 / (37 − reps))
Lander Formula (1985)
1RM = (100 × weight) / (101.3 − 2.67123 × reps)
Accuracy Tip: These formulas are most accurate when using 1–10 rep ranges. Beyond 10 reps, accuracy decreases. For best results, use a weight where you reach failure between 3–6 reps.