How accurate are 1RM calculators?
Within 2-5 lbs for 3-5 rep data. Accuracy decreases with higher rep counts.
Health Fitness
One Rep Max Calculator
Compute your estimated maximum weight you can lift for one rep across various formulas
Compare Multiple 1RM Methods
Get a thorough insight into your potential strength limit
What this calculator does
A one-rep max (1RM) calculator estimates the maximum weight you can lift for a single repetition. Knowing your 1RM helps program training using percentages (e.g., 70% of 1RM for hypertrophy). Testing actual 1RM carries injury risk, so estimation is preferred.
How it works
Enter weight lifted and reps completed. The calculator applies formulas (Brzycki, Epley) to estimate 1RM.
Formula
Brzycki: 1RM = Weight × 36 ÷ (37 - Reps). Epley: 1RM = Weight × (1 + Reps/30). Most accurate with 2-10 reps.
Tips for using this calculator
- Use 3-8 rep range for best accuracy
- Test when fresh, not fatigued
- Formulas become less accurate above 10 reps
- Retest every 4-8 weeks
- Use estimated 1RM for programming, not actual max attempts
Frequently asked questions
Should I test my actual 1RM?
Usually unnecessary and risky. Estimated 1RM is sufficient for programming. Test only if competing.
Why do different formulas give different results?
Formulas were developed from different populations and methods. Brzycki and Epley are most commonly used and similar in accuracy.