One Rep Max Calculator

Estimate your 1RM

Calculate your estimated one-rep max based on the weight and reps you can perform. Useful for programming training percentages.

kg

Enter the number of reps you completed (1-30)

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Understanding One Rep Max

What is 1RM?

One Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form. It's a key metric for measuring strength and programming training percentages. Rather than testing your true max (which can be risky), you can estimate it from submaximal lifts.

The Formulas

We use two well-established formulas and average them for better accuracy:

Epley Formula
1RM = weight × (1 + reps/30)

Best for lower rep ranges (1-6 reps)

Brzycki Formula
1RM = weight × (36 / (37 - reps))

Best for moderate rep ranges (6-10 reps)

Using Your 1RM

  • •Strength (1-5 reps): Train at 85-100% of 1RM for maximal strength
  • •Hypertrophy (6-12 reps): Train at 65-85% of 1RM for muscle growth
  • •Endurance (12+ reps): Train at 50-65% of 1RM for muscular endurance
  • •Re-test every 4-8 weeks as you get stronger

Accuracy Notes

These estimates are most accurate for 1-10 reps. Higher rep sets (10+) become less reliable for predicting 1RM because muscular endurance becomes a larger factor. For best results, use a weight you can lift for 3-6 reps with good form.