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 of an exercise with proper form. It is a key benchmark for strength training and used to program training loads at specific percentages of your max.

How is 1RM calculated?

The Brzycki formula estimates 1RM as: 1RM = weight / (1.0278 - 0.0278 × reps). It is one of the most accurate prediction equations for submaximal testing, validated in peer-reviewed research (Brzycki, 1993).

How do I use my 1RM for training?

Use your 1RM to set training loads: 60-70% for muscular endurance, 70-80% for hypertrophy (muscle growth), 80-90% for strength, and 90%+ for maximal strength. Always warm up thoroughly and use a spotter for heavy sets.

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1 RM Calculator

Calculate your one-rep max strength

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Weight Lifted

Number of Reps (1-12)

Formula: Brzycki (1993). 1RM = weight / (1.0278 - 0.0278 × reps). Always use proper form and a spotter for heavy lifts.

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Enter the weight and reps to estimate your one-rep max

Last updated: July 25, 2026Author: HealthFitCalc TeamCategory: Strength TrainingReviewed by Health Professionals

References

Brzycki, M. Strength testing: Predicting a one-rep max from a reps-to-fatigue. JOPERD 64(1): 88-90, 1993.
American College of Sports Medicine (ACSM) - Guidelines for Exercise Testing and Prescription
National Strength and Conditioning Association (NSCA) - Essentials of Strength Training and Conditioning

About 1 RM Calculator

How It Works

The 1 RM (One Rep Max) Calculator uses the Brzycki formula to estimate your maximum lifting capacity from a submaximal effort. Enter the weight you lifted and the number of repetitions performed to failure, and the calculator predicts your 1RM along with estimated weights for 1-12 repetitions.

How to Interpret Results

Your 1RM is the estimated maximum weight you can lift once with proper technique. The RM table shows estimated loads for different rep ranges. Use these percentages to structure your training: 60-70% for endurance, 70-80% for hypertrophy, and 85%+ for maximal strength development.

Training Tips

Never test your 1RM without a proper warm-up and spotter. Submaximal testing (using 3-10 reps) is safer and nearly as accurate for program design. Retest every 4-8 weeks to track progress and adjust training loads.

Limitations

The Brzycki formula is most accurate for reps between 1-12 and may overestimate for higher rep ranges. Individual variation, exercise selection, and training experience affect actual 1RM. Use the estimate as a guide, not an absolute.

HealthFitCalc TeamHealth & Fitness Editors

Last reviewed: July 25, 2026

Medical Disclaimer: This calculator is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician or qualified health provider with any questions regarding your health.