One Rep Max Calculator: Estimate Your 1RM
Free online one rep max calculator and web app. Enter the weight and reps of a set to estimate your 1RM with seven formulas, and get a percentage chart for training. Install it on your phone like an app.
What is a one rep max?
Your one rep max (1RM) is the most weight you can lift once with proper form. Lifters use it to track strength and to plan workouts, because training loads are often written as a percentage of 1RM.
1RM formulas used
| Formula | Equation (w = weight, r = reps) |
|---|---|
| Epley | w x (1 + r / 30) |
| Brzycki | w x 36 / (37 - r) |
| Lander | 100w / (101.3 - 2.67123r) |
| Lombardi | w x r^0.10 |
| Mayhew | 100w / (52.2 + 41.9 e^(-0.055r)) |
| O'Conner | w x (1 + 0.025r) |
| Wathan | 100w / (48.8 + 53.8 e^(-0.075r)) |
Training zones by % of 1RM
| Goal | % of 1RM | Typical reps |
|---|---|---|
| Strength | 85-95% | 1-5 |
| Muscle growth | 65-85% | 6-12 |
| Muscular endurance | 50-65% | 12 or more |
Staying safe
Estimating your max from a heavy set of 3 to 8 reps is safer than testing a single all-out rep. Warm up well, use a spotter or safety bars, and keep your form strict. If you have an injury or health condition, talk to a doctor or coach first.
What to do next
Fuel your training with the Protein Intake Calculator and Macro Calculator, find your calories with the TDEE Calculator, track your body fat, and check your training intensity with the Heart Rate Zone Calculator and Calories Burned Calculator. Or browse all free tools.
Frequently asked questions
What is a one rep max (1RM)?
Your one rep max is the heaviest weight you can lift for a single repetition with good form. It is used to measure strength and to set training weights as percentages.
How is 1RM calculated from reps?
Formulas such as Epley, Brzycki and Lander estimate your 1RM from the weight you lifted and the number of reps you completed. This calculator uses seven formulas and shows their average.
Which 1RM formula is the most accurate?
No single formula is best for everyone. They agree closely for sets of about 2 to 10 reps and drift apart on higher reps, so the average is a safer estimate.
Is it safe to test my true 1RM?
Testing a true max is risky without a spotter and good technique. Estimating your 1RM from a heavy set of 3 to 8 reps is a safer way to track strength.
How accurate is a 1RM calculator?
Estimates are best for sets under 10 reps. Exercise type, fatigue and training experience change the result, so treat it as a guide and retest every few weeks.
What percentage of 1RM should I train at?
Strength work is often done at 85 to 95% of 1RM for 1 to 5 reps, muscle building at 65 to 85% for 6 to 12 reps, and muscular endurance at lighter loads for higher reps.
Disclaimer: This calculator gives estimates for general information only and is not medical advice. Consult a doctor or qualified coach before starting a new training program.
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