One-Rep Max (1RM) Calculator
Your one-rep max (1RM) is the heaviest weight you can lift for a single, technically sound repetition. Testing it directly is tiring and carries more risk, so most lifters estimate it from a set of several reps. Enter a recent set below to estimate your 1RM and see training loads at common percentages.
Not medical advice. This calculator gives an educational estimate only. It does not diagnose any condition or replace advice from a doctor, registered dietitian or other licensed professional. If you are pregnant, under 18, managing a medical condition or taking medication, talk to a clinician before changing how you eat or train.
How it works
The calculator uses two of the most widely studied prediction equations and reports their average:
- Epley (1985):
1RM = weight × (1 + reps ÷ 30) - Brzycki (1993):
1RM = weight × 36 ÷ (37 − reps)
For example, 185 lb for 5 reps gives an Epley estimate of 216 lb and a Brzycki estimate of 208 lb, for an average of about 212 lb. The two formulas agree closely at low reps and drift apart as reps rise, which is why the calculator only accepts sets of 1 to 12 reps. Weight units don't change the math, so the result is in whatever unit you enter.
How to read your results
The percentage table turns your estimate into working weights. Strength-focused programs often use 80-90% of 1RM for sets of 3 to 6, while muscle-building work commonly sits around 65-80% for 6 to 12 reps. The rep column is a rough guide: people with more muscular endurance can do more reps at a given percentage. Use the table to pick a starting weight, then adjust by feel, finishing most sets with one to three reps still in reserve. If you're new to lifting, our beginner 4-week workout plan shows how to build up before chasing heavy numbers.
Limitations
- Estimates are most accurate from sets of about 10 reps or fewer taken close to failure. Sets stopped well short of failure will underestimate your max.
- Accuracy differs between exercises. Studies find the equations work better for the bench press and squat than for smaller isolation lifts or machines.
- Fatigue, sleep, technique and experience shift results day to day. Beginners' estimates change quickly as their skill improves.
- An estimate is not a reason to attempt a true max. If you do test, use a spotter or safety bars, and talk with a clinician first if you have heart, joint or blood pressure concerns.
Sources
- Brzycki M. Strength testing: predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance. 1993;64(1):88-90.
- Epley B. Poundage Chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises; 1985.
- LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. Journal of Strength and Conditioning Research. 1997;11(4):211-213.
- American College of Sports Medicine. Progression models in resistance training for healthy adults. Medicine & Science in Sports & Exercise. 2009;41(3):687-708.
- Centers for Disease Control and Prevention. Adult Activity: An Overview (muscle-strengthening recommendations).