One Repetition Maximum (1RM) Calculator | HealthCalculum
Estimate maximum load for one repetition using validated formulas
Important Medical Disclaimer
This calculator is an educational and clinical decision support tool. Results DO NOT replace professional medical evaluation, laboratory tests, or clinical judgment. Always consult a qualified healthcare professional for diagnosis, treatment, and clinical decisions. Calculations are based on scientifically validated formulas but may not be applicable to all patients.
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What is 1RM?
One Repetition Maximum (1RM) is the maximum weight that can be lifted for one complete repetition of an exercise with proper form. It is used to determine training intensities and track strength progress.
How to Calculate
Enter the weight you lifted and the number of repetitions you performed (before failure). Choose a formula (Brzycki is most common). The calculator estimates your 1RM and provides training percentages for different intensity zones.
Limitations
These formulas provide estimates and accuracy decreases above 10 repetitions. Direct 1RM testing is more accurate but carries injury risk. Always use proper form and have a spotter. Consult a fitness professional before maximum strength testing.
Frequently Asked Questions
Which formula is most accurate?
Brzycki is widely used and accurate for 2-10 reps. Epley works well for low reps (1-5). Lander is a valid alternative. Accuracy varies by individual and exercise.
Can I test 1RM directly?
Yes, but requires experience, proper warm-up, perfect technique, and a safety spotter. Formula estimates are safer for most people and adequate for training prescription.
How do I use training percentages?
50-60% for warm-up, 60-70% for muscular endurance, 70-85% for hypertrophy, 85-95% for maximum strength, >95% for testing. Adjust based on goals and periodization.
How often should I recalculate my 1RM?
Every 4-8 weeks or when you notice significant strength changes. Allows proper training load adjustment and progress tracking.
Scientific References
- 1. Brzycki M. Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue. Journal of Physical Education, Recreation & Dance. 1993;64(1):88-90.
- 2. Epley B. Poundage Chart. Boyd Epley Workout. Lincoln, NE: University of Nebraska Press; 1985.
- 3. Lander J. Maximums based on reps. NSCA Journal. 1985;6:60-61.
- 4. Baechle TR, Earle RW. Essentials of Strength Training and Conditioning. 3rd ed. Champaign, IL: Human Kinetics; 2008.