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Calculator Answers

One Rep Max Calculator

Source: Brzycki M. Strength Testing: Predicting a One-Rep Max from Reps-to-Fatigue. J Phys Educ Recreat Dance. 1993;64(1):88-90 · Source verified July 22, 2026

Blake Boege
Written by Blake Boege · Founder, Calculator Answers

A one-rep max calculator is a strength training assessment utility that estimates the maximum weight an individual can lift for a single repetition. It applies established formulas, such as Epley, Brzycki, or Lombardi equations, using submaximal weight and repetition inputs. The calculator projects the theoretical limit and compiles a training load table showing percentages of the estimated maximum. Athletes, strength coaches, and weightlifters employ it to program resistance training intensities without attempting risky maximal lifts.

Pick a unit and formula. Enter the weight lifted and the number of reps performed. The calculator returns an estimated 1RM and a training-load percentage table.

See also: Bench Press Calculator, VO2 Max Calculator, and Max Heart Rate Calculator.

Quick Answer

Estimate the maximum weight you can lift for a single repetition of any exercise. Enter the weight and reps from a completed set to view your 1RM estimation.

lb

e.g. 225

Whole number; estimates most reliable below 10 reps. · e.g. 5

1RM estimates are best for low rep counts. Brzycki only works when reps are below 37.

One-rep max

Estimated 1RM · Epley

262.5 lb

225 × (1 + 5 ÷ 30)

Lifted225 lb × 5 reps
95%249.4 lb
90%236.3 lb
85%223.1 lb
80%210 lb
75%196.9 lb
70%183.8 lb
65%170.6 lb
60%157.5 lb

Lift safely. 1RM is a planning estimate. Test or train heavy with a spotter, proper warm-up, and controlled progression. New lifters should build base strength before testing maxes.

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Examples

225 lb × 5 reps (Epley)

≈ 263 lb · 80% ≈ 210 · 90% ≈ 236

100 kg × 5 reps (Brzycki)

≈ 113 kg · 80% ≈ 90 · 90% ≈ 101

315 lb × 3 reps (Average)

≈ 343 lb · 80% ≈ 275 · 90% ≈ 309

How it works

Formula · Epley: 1RM = weight × (1 + reps / 30). Brzycki: 1RM = weight / (1.0278 − 0.0278 × reps)

Three classic formulas convert a sub-max set into a 1RM estimate. The calculator also offers their average, which evens out some of the per-formula bias. Always pair max estimates with sensible training and good form.

Epley · 1RM = weight × (1 + reps ÷ 30)

Brzycki · 1RM = weight × 36 ÷ (37 − reps)

Lombardi · 1RM = weight × reps^0.10

Brzycki himself limits it to fewer than 10 reps: he wrote that beyond about ten the relationship "is not quite linear" and the formula "is only valid for predicting a 1-RM when the number of reps-to-fatigue is less than 10". It stays defined until 37 reps, where the denominator reaches zero, but that is algebra rather than evidence.

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Lifting safety. Never test heavy lifts without proper warm-up, safe equipment, and (for true 1RM tests) a spotter. Build base strength gradually and consult a coach or clinician if you have injuries or medical conditions.

Disclaimer. Educational training estimate only. This is not medical advice or a substitute for coaching, supervision, or professional care.

Related Calculators

More tools from Health

Bench Press CalculatorEstimate your bench press 1RM from any rep set and see bench-specific training percentages with bar loads, rep targets, and program-friendly intensity ranges.VO2 Max CalculatorEstimate VO2 max from two published field tests: the Cooper 12-minute run and the Rockport 1-mile walk. Shows the equation used and the group of people it was developed in. A field-test estimate, not a laboratory measurement.Max Heart Rate CalculatorEstimate your maximum heart rate (MHR) by age using the standard 220 minus age formula and the Tanaka equation.RPE CalculatorEstimate your one-rep max (1RM) and calculate training percentages using weight, reps, and Rate of Perceived Exertion (RPE).

Frequently asked questions

1RM is the most weight you can lift for one full repetition with proper form on a given lift. Strength programs use 1RM (or estimated 1RM) to set training loads as percentages, like working sets at 70 to 85 percent.

Several formulas convert a submaximal set into a 1RM estimate. Epley: weight × (1 + reps ÷ 30). Brzycki: weight × 36 ÷ (37 − reps). Lombardi: weight × reps^0.10. The calculator also offers an average of all three. None is perfect; each performs best in different rep ranges.

All three agree well for low reps (1 to 6) and diverge with higher reps. Brzycki tends to underestimate at very high reps and is undefined at 37 reps, though its author had already ruled it out above about ten. Epley and Lombardi keep returning values at higher reps but lose accuracy. For most planning use, the average of the three is a fair pick.

Most reliable when the test set is 10 reps or fewer with crisp form. Beyond 10 to 12 reps, fatigue and technique drift make estimates noisier. Beginners should also expect more variability; max tests stabilize as form and neural adaptations improve.

Once you have an estimated 1RM, you can set working sets at fixed percentages. Hypertrophy work often sits at 65 to 80%, strength work at 80 to 95%. Peaking programs cycle higher; deload weeks pull back. Use the table as a planning starting point and adjust to perceived effort.

Direct 1RM tests are useful for experienced lifters with controlled programming. They need a spotter, thorough warm-up, and good recovery. For most people, estimated 1RM from a 3 to 8 rep set is safer and informative enough for planning.