One Rep Max Calculator
A one-rep max (1RM) calculator estimates the heaviest weight you can lift once using your performance with lighter weights, helping plan strength training safely.
Calculate Your 1RM
Your Estimated One Rep Max
Based on the Epley formula. See below for other calculation methods.
Understanding One Rep Max
Epley Formula (Most Common)
Where w is the weight lifted and r is the number of repetitions.
This formula is widely used for its simplicity and accuracy for repetitions between 1 and 10.
Brzycki Formula
This formula is considered more accurate for lower repetitions (1-5 reps). It tends to give slightly lower estimates than Epley for higher reps.
Lombardi Formula
This formula uses an exponential relationship and is particularly useful for powerlifting movements.
Formula Comparison
| Formula | Best For | Accuracy Range |
|---|---|---|
| Epley | General strength training | 1-10 reps |
| Brzycki | Lower rep ranges | 1-5 reps |
| Lombardi | Power movements | 1-10 reps |
| O'Conner | Higher rep ranges | 5-12 reps |
Important Considerations
1. These formulas provide estimates - your actual 1RM may vary based on factors like fatigue, technique, and muscle fiber composition.
2. For safety, never attempt a true 1RM without proper preparation and spotters.
3. The accuracy decreases significantly for repetitions above 12.
4. Different formulas may be better suited for different exercises.