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Fitness — Strength

One-Rep Max Calculator

Enter the weight and reps you lifted to estimate your one-rep max, with a training percentage table.

Filed by The Statistics Desk  |  Method: Epley & Brzycki 1RM
1–12 for best accuracy
Estimated 1RM
—
One-rep max (Epley).
Training percentages
Brzycki estimate—
95% × ~2 reps—
90% × ~4 reps—
85% × ~6 reps—
80% × ~8 reps—
70% × ~12 reps—
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How the One-Rep Max Calculator Works

Your one-rep max (1RM) is the most weight you can lift for a single repetition of an exercise. It is the reference point for programming strength training — most routines prescribe a percentage of 1RM — but actually testing it is risky and tiring. Instead you can estimate it from a set you have already done.

Enter the weight you lifted and how many clean reps you got. The calculator applies the two best-known formulas: Epley, weight × (1 + reps ÷ 30), and Brzycki, weight × 36 ÷ (37 − reps). It then builds a percentage table so you can pick working weights for different rep ranges. The estimates are most accurate when the set was 10 reps or fewer.

Epley: 1RM = weight × (1 + reps ÷ 30)

Frequently Asked Questions

How accurate are 1RM estimates?

Very accurate for sets of about 1 to 10 reps — usually within a few percent of a true max. Beyond ten reps, endurance and fatigue start to dominate and the formulas overestimate, so use a lower-rep set when you can.

Why do Epley and Brzycki differ?

They are different curve fits to the same relationship between reps and load. They agree closely at low reps and drift apart at higher reps. Showing both gives you a sensible range rather than a single false-precision number.

How do I use the percentage table?

Once you know your estimated 1RM, multiply it by the listed percentage to get a working weight for that rep range — for example about 85% for sets of six. It is a starting point; adjust to how the bar actually moves.

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