One rep max
calculator.
Estimate the heaviest weight you could lift once from a set you took to failure, without testing a true maximum. See all seven published equations side by side, their average and spread, and the loads for any percentage or rep target.
From 100 kg × 5 reps, the seven equations estimate a one-rep max of 112.5 kg to 119 kg, averaging 115.5 kg.
- Epley
- 116.7 kg
- Brzycki
- 112.5 kg
- Lander
- 113.7 kg
- Lombardi
- 117.5 kg
- Mayhew et al.
- 119 kg
- O’Conner et al.
- 112.5 kg
Epley: 100 × (1 + 5 ÷ 30) = 116.7; Brzycki: 100 ÷ (1.0278 − 0.0278 × 5) = 112.5; average of 7 equations = 115.5One heavy set,
seven estimates.
- Each equation turns a weight lifted for a number of reps to failure into an estimated one-rep max (1RM): Epley w × (1 + r/30), Brzycki w ÷ (1.0278 − 0.0278r), Lander 100w ÷ (101.3 − 2.67123r), Lombardi w × r^0.10, Mayhew et al. 100w ÷ (52.2 + 41.9e^(−0.055r)), O’Conner et al. w × (1 + 0.025r) and Wathen 100w ÷ (48.8 + 53.8e^(−0.075r)).
- The headline is the plain average of the seven estimates; the lowest and highest are shown so you can see how much the equations disagree.
- One rep is your 1RM by definition, so no equation is applied. Reps from 1 to 20 are accepted, and a warning appears above 10, where the equations lose accuracy.
- The load table multiplies the average 1RM by 50% to 100%. Reps to failure at each percentage come from inverting Brzycki, r = (1.0278 − %) ÷ 0.0278, and Epley, r = 30 × (1 ÷ % − 1).
- The arithmetic does not depend on the unit, so kilograms and pounds give the same result in their own unit. Loads are shown to 0.1 and rounded to your plate step in the table.
How do you calculate your one-rep max?
Lift a weight for as many clean reps as you can, then put the weight w and the reps r into an equation. The two most common are Epley and Brzycki. For 100 kg lifted 5 times, Epley gives 100 × (1 + 5 ÷ 30) = 116.7 kg and Brzycki gives 100 ÷ (1.0278 − 0.0278 × 5) = 100 ÷ 0.8888 = 112.5 kg.
The five other published equations give 112.5 to 119.0 kg for the same set, and the average of all seven is 115.5 kg, the calculator’s default. The 6.5 kg spread is a useful reminder that every estimate is approximate.
Epley: 1RM = w × (1 + r ÷ 30)
Brzycki: 1RM = w ÷ (1.0278 − 0.0278 × r)Which one-rep max formula is the most accurate?
No equation is best for everyone. Reynolds, Gordon and Robergs (2006) tested the equations on 70 men and women aged 18 to 69 in the chest press and leg press. From 5-rep sets, the linear equations all worked with similar accuracy, and Epley’s had among the smallest mean errors. Brzycki, Lander and O’Conner underestimated leg-press strength, and the curved equations of Lombardi and Mayhew were less accurate than the linear ones.
That is why this calculator shows every equation and their average instead of a single number. If the estimates agree closely, as they do for a set of 3 to 5, you can trust the result more than when they are spread out.
How many reps should you use to estimate your 1RM?
Use a heavy set of about 3 to 10 reps. Reynolds et al. found that every equation was less accurate with a 10-rep set than with a 5-rep set, and concluded that no more than 10 repetitions should be used in these equations. The effect is easy to see: 60 kg lifted 15 times gives estimates from 78.7 kg (Lombardi) to 98.2 kg (Brzycki), a spread of almost 20 kg around an average of 89.0 kg.
Count only reps with good form, in a set where one more rep would have failed. Stopping well short of failure makes every equation underestimate.
How do you work out the weight for a set of 8 from your 1RM?
Run the equations backwards: the load for r reps is the 1RM divided by the equation’s factor for r. Enter the reps you plan in “Plan a set of” to get the average across all seven. A lifter who did 225 lb for 8 has an estimated 1RM of 280.6 lb, and the load for a set of 5 is 243.1 lb, about 245 lb on the bar.
The table does the same by percentage: at 80% of 1RM, Brzycki predicts 8.2 reps to failure and Epley 7.5. Treat these as starting points. Richens and Cleather (2014) found that at 70% of 1RM in the leg press, weightlifters managed 17.9 reps and endurance athletes 39.9, so your own number can be very different.
load for r reps = 1RM ÷ factor(r)
Brzycki reps at a fraction p of 1RM: r = (1.0278 − p) ÷ 0.0278Is it safer to estimate a one-rep max than to test it?
An estimate avoids lifting a true maximum, which is why the equations were developed: Reynolds et al. note that age and medical conditions can make 1RM testing unsuitable for some people. A heavy set to failure still needs a proper warm-up, good technique and, for barbell lifts such as the bench press or squat, a spotter or safety bars. This calculator is informational only and is not training or medical advice.
Worked examples.
A set of five
100 kg for 5 reps to failure.
115.5 kg: the seven equations range from 112.5 kg to 119 kg.
Load this examplePlanning a heavier set, in pounds
225 lb for 8 reps; what should a set of 5 weigh, rounded to 5 lb?
280.6 lb estimated 1RM; a set of 5 is about 243.1 lb, or 245 lb on the bar.
Load this exampleTen reps, where Epley and Brzycki meet
80 kg for 10 reps.
104.8 kg; Epley and Brzycki both give 106.7 kg.
Load this exampleA heavy triple
140 kg for 3 reps.
153 kg: the equations range from 148.2 kg to 159.6 kg.
Load this exampleToo many reps
60 kg for 15 reps.
89 kg, but the equations range from 78.7 kg to 98.2 kg, so a heavier set would give a better estimate.
Load this exampleWhat this calculator
does not do.
- Every equation is fitted to groups of lifters. Your true 1RM can differ, and the error grows with the number of reps, for beginners, and between exercises.
- It assumes the set was taken to failure with good form. Reps left in reserve make every estimate too low.
- The reps-per-percentage column comes from two equations, not from your own testing; real rep counts at a given percentage vary widely between people.
- It is informational only, not training or medical advice. Heavy lifting needs a warm-up, good technique and a spotter.
Common questions.
What is a one-rep max?
The heaviest weight you can lift once with good form for a given exercise. It is commonly used to set training loads as percentages, such as 80% of 1RM.
What is the Epley formula?
1RM = weight × (1 + reps ÷ 30). For 100 kg × 5 it gives 116.7 kg.
What is the Brzycki formula?
1RM = weight ÷ (1.0278 − 0.0278 × reps). For 100 kg × 5 it gives 112.5 kg. At 10 reps it gives almost the same result as Epley.
Why do the formulas give different answers?
They were fitted to different groups, lifts and rep ranges, and they curve differently as reps rise. The gap is small for 3 to 5 reps and large above 10.
Does it work for any exercise?
The studies cited here tested them on the bench press, chest press and leg press. Use the result as a rough guide for other lifts, and compare like with like over time.
- Reynolds JM, Gordon TJ, Robergs RA. Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. J Strength Cond Res 2006;20(3):584–592 — Table 1 forms of the Brzycki, Epley, Lander, O’Conner, Lombardi and Mayhew equations; comparison of their accuracy; “no more than 10 repetitions should be used”
- Beia R, et al. Developing Accurate Repetition Prediction Equations for Trained Older Adults with Osteopenia. Sports (Basel) 2024;12(9):233 — Table 1 lists the Wathen equation, 100 × rep wt ÷ (48.8 + 53.8 × exp[−0.075 × reps]), alongside the others; 5–8 reps to failure was the most accurate range
- Richens B, Cleather DJ. The relationship between the number of repetitions performed at given intensities is different in endurance and strength trained athletes. Biol Sport 2014;31(2):157–161 — reps to fatigue at 70%, 80% and 90% of 1RM in the leg press differ between endurance and strength athletes
Each estimate is the weight multiplied by the equation’s factor for the reps, using the forms printed in Reynolds et al. (2006) and, for Wathen, Beia et al. (2024). The headline is the mean of the seven. Our tests compare 500 random sets with a separately written copy of every equation, check five cases worked with 50-digit decimal arithmetic, and confirm that the estimate scales with the weight, rises with the reps, and that planned loads fall as the planned reps rise.
Built and reviewed by CalculatorLab against the sources above; every worked example on this page is re-checked by our automated test suite before each release. How we build and check calculators. Found a problem? Tell us.