One Rep Max Calculator
Calculate your one-rep maximum (1RM) using multiple formulas to estimate the maximum weight you can lift for one repetition.
Input
Enter the number of reps you can perform with this weight
What is One Rep Max (1RM)?
One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition of a given exercise. It's a key metric in strength training used to determine training loads, track progress, and design workout programs.
Our calculator uses six different formulas (Epley, Brzycki, Lombardi, Mayhew, O'Conner, and Wathan) to estimate your 1RM based on the weight you can lift for multiple reps. This gives you a more accurate estimate than using a single formula.
How to Calculate Your One Rep Max
- Select your unit system (Metric or Imperial)
- Enter the weight you lifted
- Enter the number of reps you completed with that weight
- Click "Calculate One Rep Max" to see your estimated 1RM
Safety Note: Never attempt a true 1RM without proper warm-up, spotters, and safety equipment. These formulas provide estimates to help you train safely.
Understanding the Formulas
Epley Formula
One of the most popular formulas: 1RM = weight × (1 + reps/30). Works well for lower rep ranges (1-10 reps).
Brzycki Formula
Considered one of the most accurate: 1RM = weight / (1.0278 - 0.0278 × reps). Best for 1-10 rep range.
Lombardi Formula
Uses exponential calculation: 1RM = weight × reps^0.1. Good for higher rep ranges.
Mayhew Formula
More complex formula that accounts for non-linear relationship between reps and 1RM.
O'Conner Formula
Similar to Epley: 1RM = weight × (1 + reps/40). Slightly more conservative estimate.
Wathan Formula
Uses exponential decay model. Works well across various rep ranges.
Using Your 1RM for Training
- Strength Training (85-95% of 1RM): 1-5 reps for maximum strength
- Hypertrophy (70-85% of 1RM): 6-12 reps for muscle growth
- Endurance (50-70% of 1RM): 12+ reps for muscular endurance
- Recalculate your 1RM every 4-6 weeks as your strength improves
- Use the average of all formulas for the most reliable estimate
Frequently Asked Questions
Q: How accurate are 1RM calculators?
A: 1RM calculators are estimates, typically accurate within 5-10% when using weights you can lift for 2-10 reps. Accuracy decreases with higher rep counts. The average of multiple formulas provides the most reliable estimate.
Q: Should I test my actual 1RM?
A: Testing a true 1RM requires proper preparation, spotters, and safety equipment. For most people, using calculators based on submaximal lifts is safer and sufficient for programming. Only attempt true 1RM tests if you're experienced and have proper support.
Q: Which formula is most accurate?
A: The Brzycki formula is often considered most accurate for lower rep ranges (1-10), while Lombardi works better for higher reps. Using the average of all formulas gives you the most reliable estimate across different rep ranges.
Q: Can I use this for all exercises?
A: These formulas work best for compound exercises like bench press, squat, and deadlift. They may be less accurate for isolation exercises or exercises with different movement patterns.
Q: How often should I recalculate my 1RM?
A: Recalculate every 4-6 weeks as your strength improves. If you're consistently completing more reps with the same weight, it's time to recalculate and adjust your training loads.
Q: What if I can only do 1 rep?
A: If you can only do 1 rep, that weight is very close to your actual 1RM. However, these calculators work best with 2-10 reps. For 1 rep, the estimate will be less accurate.
Related Calculators
Explore more calculators that might interest you
Wilks Score Calculator
Calculate your powerlifting strength score
Body Fat Calculator
Track your body fat percentage
Lean Body Mass Calculator
Calculate your lean body mass
Protein Calculator
Calculate your protein needs
Macro Calculator
Break down your macros
TDEE Calculator
Calculate your daily calorie needs