What is a One Rep Max (1RM)?

A One Rep Max (1RM) is the maximum amount of weight you can lift for a single repetition with proper form. It's a standard measure of muscular strength used to design training programs, track progress, and compare strength levels between individuals or across different exercises.

Which 1RM formula is the most accurate?

The Brzycki and Epley formulas are generally considered the most accurate for reps under 10. For higher rep ranges (10+), the Wathan formula tends to be more accurate. Using an average of multiple formulas often provides the best estimate. All formulas become less accurate above 10-12 reps.

How do I use my 1RM for training?

Your 1RM is used to calculate training loads. For strength training, work at 85-100% of 1RM for 1-5 reps. For hypertrophy (muscle growth), use 65-85% for 6-12 reps. For muscular endurance, use 50-65% for 15+ reps. These percentages help ensure you're training at the appropriate intensity for your goals.

Is it safe to test my actual 1RM?

Testing a true 1RM carries some injury risk, especially for beginners. It's safer to estimate your 1RM using submaximal lifts (3-10 reps) with this calculator. If you do test directly, always use a spotter, proper warm-up, and good form. Beginners should use estimates for at least 6-12 months before attempting true max tests.

Why do different formulas give different results?

Different 1RM formulas were developed using different study populations and methodologies. Some work better for certain rep ranges or experience levels. The variation between formulas typically increases with higher rep counts. Using an average of multiple formulas helps account for individual differences.

One Rep Max Calculator

Estimate your one rep max (1RM) using multiple proven formulas. Enter the weight lifted and number of reps to calculate your maximum strength.

Exercise (optional)

Weight Lifted

lbs

Repetitions Performed

reps

Your Bodyweight (optional)

lbs

Used for strength level estimation

Estimated One Rep Max

lbs

Average of 7 formulas

Strength Level for Bench Press

Beginner Novice Intermediate Advanced Elite

Formula Comparison

Epley

Brzycki

Lander

Lombardi

Mayhew

O'Conner

Wathan

Training Load Chart

% of 1RM	Reps	Intensity	Weight

Training Zones

Strength

0 - 0

85-100% 1RM | 1-5 reps

Hypertrophy

0 - 0

65-85% 1RM | 6-12 reps

Endurance

0 - 0

50-65% 1RM | 15+ reps

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Understanding One Rep Max

Your One Rep Max (1RM) is the maximum weight you can lift for a single repetition with proper form. It's a fundamental measurement in strength training used to design programs, track progress, and compare strength levels.

The Formulas Used

This calculator uses 7 different scientifically-validated formulas to estimate your 1RM:

Epley: weight x (1 + reps/30)
Brzycki: weight x (36 / (37 - reps))
Lander: (100 x weight) / (101.3 - 2.67123 x reps)
Lombardi: weight x reps^0.1
Mayhew: (100 x weight) / (52.2 + 41.9 x e^(-0.055 x reps))
O'Conner: weight x (1 + reps/40)
Wathan: (100 x weight) / (48.8 + 53.8 x e^(-0.075 x reps))

Which Formula is Best?

Brzycki & Epley: Most accurate for lower rep ranges (1-10 reps)
Wathan: Better accuracy for higher rep ranges (10+ reps)
Average: Using the average of all formulas provides the most reliable estimate

Using Your 1RM

Once you know your estimated 1RM, you can use percentages to plan your training:

Strength (85-100%): Heavy weights, low reps (1-5). Builds maximum strength and neural adaptations.
Hypertrophy (65-85%): Moderate weights, medium reps (6-12). Optimal for muscle growth.
Endurance (50-65%): Lighter weights, high reps (15+). Improves muscular endurance and work capacity.

Accuracy Notes

These formulas are most accurate when:

Using rep ranges between 2-10 repetitions
The set was taken close to failure (within 1-2 reps)
Proper form was maintained throughout

Important: All formulas become less accurate above 10-12 reps. For best results, use a weight you can lift for 3-10 reps with good form, taken close to muscular failure.