How accurate is a calculated 1RM?

Within ~5% for sets of 1–10 reps. Beyond 10 reps, accuracy drops because endurance becomes a bigger factor than max strength.

Should I actually test my 1RM?

Only if you are experienced and warmed up properly. Calculated 1RM is safer for programming sets and percentage-based training.

How do I use 1RM for programming?

5×5 strength work uses 75–85% of 1RM. Hypertrophy (8–12 reps) uses 65–75%. Endurance (15+ reps) uses 50–65%.

One Rep Max Calculator

Type the weight you lifted and how many reps you completed. The calculator estimates your 1RM and the corresponding training percentages.

By Numerly · Updated June 14, 2026

Unit

Weight lifted

Reps completed

Estimated 1RM

257.813 lb

Training percentages

95% – Heavy single	244.922 lb
85% – Strength (5×5)	219.141 lb
75% – Hypertrophy (4×8)	193.359 lb
65% – Volume (3×12)	167.578 lb

How it works

Two formulas are commonly used. Brzycki: 1RM = weight × 36 ÷ (37 − reps). Epley: 1RM = weight × (1 + reps ÷ 30). Brzycki tends to be more accurate at low reps; Epley at higher reps. We average them for a middle-of-the-road estimate.

Frequently asked

How accurate is a calculated 1RM?: Within ~5% for sets of 1–10 reps. Beyond 10 reps, accuracy drops because endurance becomes a bigger factor than max strength.
Should I actually test my 1RM?: Only if you are experienced and warmed up properly. Calculated 1RM is safer for programming sets and percentage-based training.
How do I use 1RM for programming?: 5×5 strength work uses 75–85% of 1RM. Hypertrophy (8–12 reps) uses 65–75%. Endurance (15+ reps) uses 50–65%.

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