performance
One rep max calculator
What is one rep max?
Your one rep max (1RM) is the maximum weight you can lift for a single repetition with good form on a given exercise. It is the standard measure of absolute strength in powerlifting and strength training.
How to use this calculator
- Enter the weight you lifted and the number of reps you completed.
- Click Calculate 1RM to see estimates from three formulas.
- Use 3–10 rep sets for the most accurate estimates — accuracy drops above 10 reps.
- The average of the three formulas is the most reliable single number.
The formulas
Epley
1RM = weight × (1 + reps / 30)
Brzycki
1RM = weight × (36 / (37 − reps))
Lombardi
1RM = weight × reps^0.1
The three formulas are averaged to reduce individual formula bias.
How to interpret your result
These are estimates — your true 1RM may differ by 5–10%. Use the estimate for programming percentages (e.g., work sets at 75–85% of 1RM). Re-test every 4–8 weeks to track progress.
Related tools
- Wilks Score Calculator — compare your strength across bodyweights
- VO2 Max Calculator — measure your aerobic capacity
Read more
What is one rep max?
Your one rep max (1RM) is the maximum weight you can lift for a single repetition with good form on a given exercise. It is the standard measure of absolute strength in powerlifting and strength training.
How to use this calculator
- Enter the weight you lifted and the number of reps you completed.
- Click Calculate 1RM to see estimates from three formulas.
- Use 3–10 rep sets for the most accurate estimates — accuracy drops above 10 reps.
- The average of the three formulas is the most reliable single number.
The formulas
Epley
1RM = weight × (1 + reps / 30)
Brzycki
1RM = weight × (36 / (37 − reps))
Lombardi
1RM = weight × reps^0.1
The three formulas are averaged to reduce individual formula bias.
How to interpret your result
These are estimates — your true 1RM may differ by 5–10%. Use the estimate for programming percentages (e.g., work sets at 75–85% of 1RM). Re-test every 4–8 weeks to track progress.
Related tools
- Wilks Score Calculator — compare your strength across bodyweights
- VO2 Max Calculator — measure your aerobic capacity
Frequently asked questions
How accurate are 1RM calculators?
At 3–6 reps, estimated 1RM is within 2–5% of tested 1RM. Above 10 reps, accuracy drops because muscular endurance becomes the limiter instead of maximum strength. Use low-rep sets for the most accurate estimate.
Which formula is most accurate: Epley, Brzycki, or Lombardi?
Epley tends to estimate slightly higher, Brzycki slightly lower, and Lombardi sits in between. The three are within 5% of each other in the 1–10 rep range. Use the average for the best single estimate.
Should I actually test my 1RM?
Testing a true 1RM is high-risk and fatiguing. For most trainees, a calculated 1RM from a 3–5 rep max set is safer and within 2–3% of a tested max.
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