ARC calculator

1RM Calculator

Estimate a one-rep max from a 1–10 rep set using three formulas. The headline number is the median.

These results are estimates, not guarantees. ARC is an educational fitness-planning product, not medical treatment.

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How Accurate Is a 1RM Calculator?
RPE vs RIR

How 1RM is estimated

Epley: weight × (1 + reps / 30). Brzycki: weight × 36 / (37 − reps). Lombardi: weight × reps^0.10. One rep equals the weight entered. The headline is the median. The range is the formula spread. Use 1–10 reps. RPE is shown as approximate RIR and does not rewrite the math.

How this is calculated

These are named prediction equations, not a tested max.
Plate rounding is 2.5 kg or 5 lb so the table matches a bar you can load.