One Rep Max Calculator
Estimate your 1RM strength
Formula
Epley: 1RM = W × (1 + R/30)
Brzycki: 1RM = W × 36/(37-R)
Most accurate with 1-10 reps
Training Percentages
| Strength (1-5) | 85-100% |
| Hypertrophy (6-12) | 65-85% |
| Endurance (15+) | 50-65% |
Related
Complete Guide to One Rep Max Calculator
Your One Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form. Knowing your 1RM helps you program training at appropriate intensities for strength, hypertrophy, or endurance goals.
Why Calculate Instead of Test?
Testing actual 1RMs carries injury risk, requires spotters, and causes significant fatigue. Estimation formulas let you work with submaximal weights (3-10 reps) to predict your max safely. The results are accurate within 5% for most people.
Using Your 1RM for Training
- Strength (1-5 reps): Work at 85-100% of 1RM
- Hypertrophy (6-12 reps): Work at 65-85% of 1RM
- Endurance (15+ reps): Work at 50-65% of 1RM
Formula Accuracy
Formulas are most accurate in the 3-10 rep range. Above 10 reps, error increases significantly. Different formulas perform better for different people - Epley tends to work well for most, while Brzycki may be better for very strong individuals.
Progressive Overload
Recalculate your 1RM every 4-8 weeks as you get stronger. The goal is progressive overload - gradually increasing weight or reps over time to drive adaptation.
Frequently Asked Questions
Most accurate in the 1-6 rep range (within 5%). Accuracy decreases as reps increase. Above 10 reps, error can be 10-15%. Use formulas as estimates, not absolutes.
Not necessary for most people. Testing requires proper warmup, spotters, and carries injury risk. Use calculated estimates and adjust based on how weights feel in training.
Epley works well for most people. Brzycki may be better for very strong lifters. This calculator averages multiple formulas. The differences are usually small (2-5%).
Every 4-8 weeks or when you set a new rep PR. As you get stronger, your calculated 1RM should increase, which means your working weights should too.
Strength: 85-95% for 1-5 reps. Hypertrophy: 70-85% for 6-12 reps. Endurance: 60-70% for 12+ reps. These are guidelines - adjust based on how you feel.
Factors like technique, fatigue, nervous system efficiency, and muscle fiber type affect actual vs predicted. Some people can grind out heavy singles while others excel at rep work.
Yes. Each lift has its own 1RM. You might bench 80kg for 5 but only squat 70kg for 5. Calculate and track each major lift separately.