One Rep Max Calculator

Estimate your one-rep max (1RM) for any lift using seven scientifically validated formulas: Epley, Brzycki, Lander, Lombardi, Mayhew, O'Conner, and Wathan. View training zone percentages and compare formula results.

Enter Your Lift

Exercise

Unit

Weight Lifted (lbs)

Reps Performed (1-30)

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Enter the weight you lifted and how many reps you completed to estimate your one rep max across 7 proven formulas.

About the Formulas

Epley (1985)weight x (1 + reps/30)

One of the most widely used formulas. Works best for rep ranges of 1-10. Tends to overestimate at higher rep counts.

Brzycki (1993)weight x 36 / (37 - reps)

Very popular in academic and professional settings. Most accurate in the 1-10 rep range. Produces identical results to Epley at 10 reps.

Lander (1985)100 x weight / (101.3 - 2.67123 x reps)

A linear regression model. Provides consistent estimates across moderate rep ranges.

Lombardi (1989)weight x reps^0.10

A power-law based formula. Tends to give more conservative estimates compared to other formulas.

Mayhew et al. (1992)100 x weight / (52.2 + 41.9 x e^(-0.055 x reps))

Developed using collegiate football players. Uses an exponential model for a good fit across wider rep ranges.

O'Conner et al. (1989)weight x (1 + 0.025 x reps)

A simple linear model. Generally provides the most conservative estimates and works well for low rep ranges.

Wathan (1994)100 x weight / (48.8 + 53.8 x e^(-0.075 x reps))

An exponential model that tends to produce slightly higher estimates. Often used alongside Epley and Brzycki for comparison.

Disclaimer: These formulas provide estimates only. Actual 1RM may vary based on training experience, fatigue, technique, and individual biomechanics. Always use a spotter when attempting maximal lifts. Consult a qualified trainer before testing your one rep max.

How to Use One Rep Max Calculator

1Select your exercise (bench press, squat, deadlift, or overhead press).
2Enter the weight you lifted and the number of reps completed.
3View your estimated 1RM across all 7 formulas.
4Use the training zone chart to plan your workout weights.

Frequently Asked Questions

What is a one rep max (1RM)?▾

Your one rep max is the maximum weight you can lift for a single repetition with proper form. It's used to set training percentages and track strength progress.

Which 1RM formula is most accurate?▾

The Epley and Brzycki formulas are considered most accurate for reps under 10. For higher rep ranges (10+), the Wathan and Mayhew formulas tend to be more reliable. This calculator shows all seven for comparison.

How do I use 1RM percentages for training?▾

Common training zones: 90-100% for maximal strength (1-3 reps), 75-85% for strength/hypertrophy (4-8 reps), 65-75% for hypertrophy (8-12 reps), and 50-65% for endurance (12+ reps).

About One Rep Max Calculator

NexTool's One Rep Max Calculator is completely free to use with no sign-up required. Your data is processed directly in your browser and never sent to our servers, ensuring complete privacy and instant results.