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.

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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