1RM Calculator (One-Rep Max)

Calculates the maximum load an athlete can lift for a single repetition without the injury risk of direct 1RM testing.

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Result

Average 1RM (Epley + Brzycki): 115 kg
Epley Formula (1985): 117 kg
Brzycki Formula (1993): 113 kg
Lombardi Formula (1989): 118 kg
Wathan Formula (1994): 117 kg
Mayhew et al. Formula (1992): 119 kg
100% 1RM (~ 1 reps): 115 kg
95% 1RM (~ 2 reps): 109 kg
90% 1RM (~ 4 reps): 103 kg
85% 1RM (~ 6 reps): 97 kg
80% 1RM (~ 8 reps): 92 kg
75% 1RM (~ 10 reps): 86 kg

1RM is an estimated maximum effort. A thorough warm-up and spotters are required before attempting heavy lifts.

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How it is calculated

One-rep max estimation utilizes regression equations modeling repetitions-to-fatigue against percentage of maximal effort. The Epley formula excels in the 2–6 repetition range, while the Brzycki equation provides high accuracy across 6–10 repetitions.

Formula

Epley: 1RM = Weight × (1 + 0.0333 × Reps); Brzycki: 1RM = Weight / (1.0278 − 0.0278 × Reps); Lombardi: Weight × Reps^0.10; Wathan: (100 × Weight) / (48.8 + 53.8 × e^(−0.075 × Reps)).

Limits of the method

Not validated for sets beyond 10–12 repetitions due to localized metabolic fatigue. Precision depends on technical execution and muscle fiber composition.

Sources of the method

This calculation is for reference only and is not medical advice, a diagnosis or a prescription. If you have a medical condition, are pregnant, take medication or have any doubts, discuss the result with a physician or a qualified nutrition professional.

How to Accurately Determine 1RM Without Health Risks

Perform a thorough warm-up

Perform general joint mobility drills, followed by 3–4 warm-up sets progressively ramping up to your working weight.

Perform a working set of 3–6 reps

Select a load with which you can complete 3 to 6 clean repetitions leaving no more than 1 rep in reserve (RPE 9).

Input data and apply percentages

Enter the weight and reps into the calculator. Use the percentage chart to prescribe weights for strength (85%), hypertrophy (75%), or recovery (60%) workouts.

Application Examples in Strength Training

Bench Press100 kg × 5 reps

1RM Calculation in the Bench Press

An athlete benches 100 kg for 5 repetitions to failure. The Epley formula estimates 116.7 kg, Brzycki estimates 112.5 kg. Average result is 114.6 kg.

Working weight for a 5×5 protocol (80% 1RM) would be 92.5 kg.

Squat140 kg × 3 reps

Low-Repetition Strength Set

With 3 reps at 140 kg, calculated 1RM is 154 kg. A low rep count minimizes formula estimation error.

For a 3×3 strength phase (87% 1RM), the working weight would be 135 kg.

Deadlift180 kg × 8 reps

Higher-Repetition Set to Failure

At 8 reps, calculated maximum is ~228 kg. Here the Brzycki formula provides a more conservative and safer estimate.

Retesting with 3–5 repetitions is recommended to verify accuracy.

Why You Shouldn't Directly Test True 1RM Every Workout

Directly testing a true maximum places immense strain on tendons, ligaments, and the central nervous system, requiring 7 to 14 days of full recovery. A submaximal test of 3–5 reps carries less than a 3–5% margin of error while sparing CNS fatigue.

Difference Between Epley and Brzycki

The Epley formula linearly extrapolates fatigue (~3.33% drop per rep). The Brzycki formula accounts for non-linear power reduction, avoiding overestimation at 8–10 reps compared to Epley.

1RM Percentage Chart and Training Objectives

% of 1RM	Target Repetitions	Primary Training Objective
95–100%	1–2	Peak maximal strength, nervous system adaptation
85–90%	3–5	Strength development and myofibrillar hypertrophy
80%	6–8	Classic strength hypertrophy (muscle mass)
75%	8–10	Muscle hypertrophy and capillary density
70%	10–12	Sarcoplasmic hypertrophy, pump
65%	15	Strength endurance, motor pattern refinement
60%	20	Speed-strength work (dynamic effort)
50%	25+	Warm-up, active recovery, rehabilitation

Actual repetitions at a given percentage are individual and depend on the ratio of fast-twitch (Type II) to slow-twitch (Type I) muscle fibers.

Frequently asked questions

What repetition count yields the most accurate 1RM prediction?

Formulas yield the most accurate results in the range of 2 to 5 repetitions. Beyond 8–10 repetitions, individual muscular endurance skews the calculation.

Are the formulas identical for bench press, squat, and deadlift?

Mathematical coefficients were derived as an average across all compound lifts. In multi-joint movements with long ranges of motion (deadlift, squat), many athletes can perform more reps at 80% than in the bench press.

What is RPE and why is it important in 1RM testing?

RPE (Rating of Perceived Exertion) is a scale of perceived effort from 1 to 10. RPE 10 indicates complete failure (0 reps in reserve), RPE 9 means 1 rep in reserve. If a set was performed at RPE 8 (2 reps in reserve), add 2 to your rep count for the formula.

Is it safe to attempt lifting the calculated 1RM in practice?

Only with sound technique, a thorough warm-up, safety racks, and experienced spotters. Beginners should not attempt a true 1RM in practice.

How often should 1RM be retested?

Retesting is typically done at the end of a training mesocycle (every 4–8 weeks) using a planned test set with reps in reserve.

Evaluate your strength coefficients in powerlifting or calculate your basal metabolic rate:

Powerlifting Coefficients Calculator (DOTS, Wilks, IPF GL) →Katch-McArdle BMR & TDEE Calculator →FFMI Calculator (Fat-Free Mass Index) →Maximum Muscular Potential Calculator (Casey Butt & Berkhan) →

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What next

Formula breakdowns, biomarker reference ranges and nutrition articles with cited sources are in the NutriFit knowledge base.

Go to the knowledge base