One Rep Max Calculator
Estimate your 1RM from a set of reps, compare formulas, and generate a training percentage table.
What is one-rep max?
One-rep max (1RM) is the maximum weight you can lift for a single repetition with good form. Because testing a true 1RM can be demanding, many lifters estimate it from a submax set (for example, 5 reps) using formulas.
1RM formulas explained
Different formulas (Epley, Brzycki, Lombardi, O’Conner, Mayhew, Wathan) estimate your 1RM in slightly different ways. Estimates are generally most reliable for lower rep ranges, often 1–10 or 1–12 reps.
How to use training percentages
Training plans often use percentages of 1RM (for example, 70–85%) for working sets. Use the percentage table to pick target weights for your session, and adjust based on how you feel, the exercise, and your current fatigue.
Frequently Asked Questions
Quick answers about 1RM and training percentages.
What is one-rep max (1RM)?
1RM is the maximum weight you can lift for one rep with good form.
How do you calculate 1RM?
You enter weight and reps, then apply a 1RM formula such as Epley or Brzycki to estimate your max.
Which 1RM formula is most accurate?
Accuracy can vary by person and exercise. Comparing multiple formulas and using the average can be a practical approach.
Can I estimate 1RM from 10–12 reps?
Yes, but estimates become less reliable as reps increase. Treat high-rep estimates as rough guidance.
How do I use 1RM for training?
Many programs use percentages of 1RM to set working weights. Use the percentage table and adjust based on performance.
Disclaimer
This calculator provides estimates for informational purposes only. Training decisions should consider technique, experience, fatigue, and safety. If you have any medical concerns, consult a qualified professional.