One-rep max (1RM) from a set of reps with the Epley, Brzycki, Lombardi and O'Conner equations, plus training loads from 50 % to 100 %.
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100 kg for 5 reps points to a one-rep max of about 114.8 kg (253.1 lb); the four equations range from 112.5 to 117.5 kg.
| % of 1RM | kg | lb | Reps (Epley) |
|---|---|---|---|
| 100 % | 114.8 | 253.1 | 1 |
| 95 % | 109 | 240.4 | 2 |
| 90 % | 103.3 | 227.7 | 3 |
| 85 % | 97.6 | 215.1 | 5 |
| 80 % | 91.8 | 202.4 | 8 |
| 75 % | 86.1 | 189.8 | 10 |
| 70 % | 80.3 | 177.1 | 13 |
| 65 % | 74.6 | 164.5 | 16 |
| 60 % | 68.9 | 151.8 | 20 |
| 55 % | 63.1 | 139.2 | 25 |
| 50 % | 57.4 | 126.5 | 30 |
Loads are in kilograms; pounds are converted at 1 lb = 0.45359237 kg.
A one-rep max (1RM) is the heaviest load you can lift once with good form. It is estimated here from a set taken to failure with four equations: Epley, weight × (1 + reps ÷ 30); Brzycki, weight × 36 ÷ (37 − reps); Lombardi, weight × reps^0.10; and O'Conner, weight × (1 + 0.025 × reps). The main result is their mean, shown in kilograms and pounds.
Lifters use it to set training loads without a maximal attempt. With the default 100 kg for 5 reps, the four equations give 112.5 to 117.5 kg and a mean of 114.8 kg; the table then lists loads from 50 % to 100 % of that, with the reps Epley predicts at each.
The equations were fitted to groups of lifters and lose accuracy as reps rise, especially past 10. They are lift-specific, so an estimate from the bench press says nothing about the squat.
Lift a weight for as many clean reps as you can in one set, then apply Epley's formula: 1RM = weight × (1 + reps ÷ 30). 100 kg for 5 reps gives 100 × (1 + 5 ÷ 30) = 116.7 kg. Estimates hold up best for sets of 10 reps or fewer.
Averaging four published formulas gives 114.8 kg for the same set. Lifters use the estimate to set training loads without attempting a maximal lift.
With w the weight lifted and r the reps, for 100 kg lifted 5 times:
The mean of the four is 114.8 kg. Divide kilograms by 0.45359237 for pounds: 253.1 lb.
The formulas work the same in pounds. 225 lb for 10 reps gives 300 lb by Epley and Brzycki, 283.3 lb by Lombardi and 281.25 lb by O'Conner, a mean of 291.1 lb.
Epley and Brzycki agree exactly at 10 reps. Below 10, Brzycki gives the lower figure; above 10, the higher one.
Brzycki's 1993 paper set out his equation for predicting a max from reps to fatigue. LeSuer and colleagues (1997) later tested prediction equations in the bench press, squat and deadlift.
The imperial example is 225 lb for 10 reps, and the single-rep example 140 kg lifted once.
| Scenario | Estimated mean (kg) | Estimated mean (lb) |
|---|---|---|
| Default | 114.8 | 253.1 |
| Imperial ten reps | 132.1 | 291.1 |
| Single rep | 140.0 | 308.6 |
A single completed rep is already a one-rep max, so all four formulas return the weight lifted. Epley and O'Conner would otherwise add 3.3 % and 2.5 % at one rep.
The formulas agree at low reps and pull apart as reps rise:
Brzycki's denominator, 37 − r, shrinks toward zero as reps climb, which is why it runs away at high counts. For a usable estimate, test with a heavier set of 3 to 8 reps.
Solving Epley's formula for reps gives the reps you might manage at a percentage of your max: reps = 30 × (100 ÷ percentage − 1).
For the 114.8 kg estimate, 80 % is 91.8 kg and 70 % is 80.3 kg. Real rep counts at a given percentage vary between lifts and between lifters.
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Checked against: decimal/math: 100(1 + 5/30), 100·36/32, 100·5^0.1, 100(1 + 0.125); mean of the four
Checked against: 225 lb = 102.0582833 kg; Epley 300 lb = 136.0777 kg; Lombardi 225·10^0.1 lb; mean 291.127 lb
Checked against: Convention stated in the steps: r = 1 returns the lifted weight for every equation (Brzycki and Lombardi give it exactly)
Checked against: decimal/math: 60·1.4, 60·36/25, 60·12^0.1, 60·1.3; mean 81.3313
Lift a weight for as many clean reps as possible in one set, then apply an equation. Epley's is weight × (1 + reps ÷ 30), so 100 kg for 5 reps gives 116.7 kg; Brzycki's is weight × 36 ÷ (37 − reps), giving 112.5 kg. This calculator averages Epley, Brzycki, Lombardi and O'Conner, which gives 114.8 kg for that set.
None is best for every lift or lifter, and they agree most at low reps. For 100 kg lifted 5 times the four span 112.5 to 117.5 kg, a 5 kg spread; for 60 kg lifted 12 times they span 76.9 to 86.4 kg, almost 10 kg. Estimates from sets of 10 reps or fewer are therefore more consistent, and the mean used here sits between the highest and lowest equation.
About 8, by the Epley equation solved for reps: 30 × (100 ÷ 80 − 1) = 7.5, rounded to 8. The table under the result lists loads and Epley rep estimates from 50 % to 100 %: at 90 % it gives 3 reps and at 70 % it gives 13. Real rep counts at a given percentage vary between lifts and between lifters.
For information only, not medical advice. These formulas describe populations, not you; talk to a clinician before acting on a result.
This calculator includes 4 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.