One-Rep Max Calculator

Estimate your one-rep max from any weight and rep count. Uses three proven formulas and shows training percentages for programming your workouts.

What is a One-Rep Max?

Your one-rep max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It's a key metric for measuring strength and programming training intensity.

Formulas Used

  • Epley: 1RM = weight × (1 + reps / 30)
  • Brzycki: 1RM = weight × 36 / (37 − reps)
  • Lombardi: 1RM = weight × reps0.10

How to Use Training Percentages

  • 90-100%: Maximal strength (1-3 reps)
  • 80-90%: Strength and power (3-6 reps)
  • 70-80%: Hypertrophy / muscle growth (6-12 reps)
  • 60-70%: Muscular endurance (12-15+ reps)

Want to dial in your nutrition? Calculate your TDEE or find your daily protein needs.

Frequently Asked Questions

What is a one-rep max (1RM)?
A one-rep max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It is the gold standard for measuring maximal strength and is used to program training intensity by calculating percentages for different rep ranges.
How accurate are 1RM calculator formulas?
1RM formulas are most accurate when using sets of 10 reps or fewer. Accuracy decreases with higher rep counts. The Epley and Brzycki formulas are the most widely validated. Using the average of multiple formulas (as this calculator does) improves the estimate.
Should I test my actual 1RM or use a calculator?
For most people, using a calculator with a 3-5 rep set is safer and nearly as accurate as testing a true 1RM. Actual 1RM testing carries higher injury risk and should only be done with proper warm-up, a spotter, and experience with heavy singles.