How is one-rep max estimated?

Using formulas like Epley or Brzycki based on a weight lifted for multiple reps.

Why estimate 1RM instead of testing directly?

Directly testing carries injury risk, so submaximal-rep formulas offer a safer estimate.

How accurate are these formulas?

Reasonably accurate for lower rep ranges (2-6), less reliable at higher rep counts.

One-Rep Max (1RM) Calculator - CalculatorLabs.net

One-Rep Max (1RM) Calculator

Estimate your maximum lift safely from a lighter set, with ready-made training percentages.

Weight Lifted (lb)

Reps Completed

Formula

Estimated 1-Rep Max-

85% (Strength Set)-

70% (Hypertrophy Set)-

50% (Warm-up Set)-

What Is a One-Rep Max Calculator?

Your one-rep max (1RM) is the maximum weight you could lift for a single repetition of an exercise. Rather than testing this directly (which carries injury risk), lifters estimate it from a lighter set taken to or near failure, using a proven prediction formula. Coaches then use percentages of the 1RM to program strength, hypertrophy, and warm-up sets.

A barbell loaded with plates — the basis for 1RM strength testing.

Formulas Used

Epley: 1RM = Weight × (1 + Reps ÷ 30)
Brzycki: 1RM = Weight × 36 ÷ (37 − Reps)

How to Use This Calculator

Enter the weight you lifted for a set taken close to failure.
Enter the number of clean reps you completed with that weight (works best under 10 reps).
Choose the Epley or Brzycki formula (both give similar estimates).
Click "Calculate 1-Rep Max" to see your estimated max along with common training percentages.

Worked Example

Example: You lift 185 lb for 5 reps. Using Epley: 1RM = 185 × (1 + 5/30) = 185 × 1.167 = ~216 lb.