One Rep Max Calculator
Enter a hard set you did and see the most you could likely lift for one rep, plus the weights to use for every training percentage.
Plan a set by RPE
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Plate calculator
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How your one rep max is worked out
A hard set tells a formula how strong you are, so it can estimate the most you could lift once.
- 1
Your set
100 kg × 5 reps
to failure - 2
Epley formula
100 × (1 + 5 ÷ 30)
weight × rep factor - 3
Your 1RM
≈ 116.7 kg
range 112.5–119 - 4
Train by %
80% = 92.5 kg
about 8 reps
Read more: the formulas, a worked example and the RPE chart
Your one rep max (1RM) is the heaviest weight you can lift once, with good form, for one exercise. Testing it directly is tiring and carries more risk, so most lifters estimate it from a harder set of a few reps. Each formula below was fitted to lifters' real results: it turns "this weight for this many reps" into the weight you could most likely lift once. In Advanced you can compare all seven, use RPE (how many reps you had left), plan your next set and see the plates to load.
The formula
One rep max (Epley) = weight × (1 + reps ÷ 30)
Training weight = one rep max × percentage
With RPE: reps used = reps done + reps you had left
| Formula | One rep max from weight w and reps r |
|---|---|
| Epley (1985) | w × (1 + r ÷ 30) |
| Brzycki (1993) | w × 36 ÷ (37 − r) |
| Lombardi (1989) | w × r^0.10 |
| Mayhew (1992) | 100w ÷ (52.2 + 41.9e^(−0.055r)) |
| O'Conner (1989) | w × (1 + 0.025r) |
| Wathan (1994) | 100w ÷ (48.8 + 53.8e^(−0.075r)) |
| Lander (1985) | 100w ÷ (101.3 − 2.67123r) |
A single rep is already a one rep max, so for 1 rep every formula here gives the weight you lifted. Epley and O'Conner are straight lines; Brzycki and Lander climb faster at high reps; Mayhew and Wathan curve; Lombardi grows slowly.
Worked example
You bench 100 kg for 5 reps, with nothing left (RPE 10). Epley gives 100 × (1 + 5 ÷ 30) = 100 × 1.1667 = 116.7 kg. The others: Brzycki 100 × 36 ÷ 32 = 112.5 kg; Lombardi 100 × 5^0.1 = 117.5 kg; Mayhew 10,000 ÷ (52.2 + 41.9 × 0.7596) = 10,000 ÷ 84.03 = 119.0 kg; O'Conner 100 × 1.125 = 112.5 kg; Wathan 10,000 ÷ (48.8 + 53.8 × 0.6873) = 10,000 ÷ 85.78 = 116.6 kg; Lander 10,000 ÷ (101.3 − 13.36) = 10,000 ÷ 87.94 = 113.7 kg. The average of all seven is 115.5 kg, and the spread is 112.5 to 119.0 kg.
Your set was 100 ÷ 116.7 = 86% of your max. For sets of about 8 you'd use 80%: 116.7 × 0.8 = 93.3 kg, rounded to 92.5 kg so it can be loaded. On a 20 kg bar that's (92.5 − 20) ÷ 2 = 36.25 kg a side: 25 + 10 + 1.25.
If those 5 reps were at RPE 8 (2 reps left), every formula works from 5 + 2 = 7 reps instead: Epley gives 100 × (1 + 7 ÷ 30) = 123.3 kg. The RPE chart says 5 reps at RPE 8 is 81.1% of max, so 100 ÷ 0.811 = 123.3 kg too.
Percentage of 1RM chart
| % of 1RM | Reps most people can do |
|---|---|
| 100% | 1 |
| 95% | 2 |
| 90% | 3 |
| 85% | 5 |
| 80% | 8 |
| 75% | 10 |
| 70% | 13 |
| 65% | 16 |
| 60% | 20 |
| 55% | 25 |
| 50% | 30 |
Reps come from turning Epley around: reps = 30 × (100 ÷ percentage − 1), rounded. Real results vary with the lift, your training and your muscle fibre mix: many people can do more reps on squats and leg press than on bench press at the same percentage.
The RPE chart
RPE (rate of perceived exertion) rates a set from 1 to 10 by how many reps you had left: RPE 10 = none, 9 = one, 8 = two, and half points for "maybe one more". This is the commonly used chart popularised by powerlifting coach Mike Tuchscherer (Reactive Training Systems). It is one sequence: 5 reps at RPE 8 sits in the same place as 7 reps at RPE 10.
| RPE | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 10 | 100.0 | 95.5 | 92.2 | 89.2 | 86.3 | 83.7 | 81.1 | 78.6 | 76.2 | 73.9 | 70.7 | 68.0 |
| 9.5 | 97.8 | 93.9 | 90.7 | 87.8 | 85.0 | 82.4 | 79.9 | 77.4 | 75.1 | 72.3 | 69.4 | 66.7 |
| 9 | 95.5 | 92.2 | 89.2 | 86.3 | 83.7 | 81.1 | 78.6 | 76.2 | 73.9 | 70.7 | 68.0 | 65.3 |
| 8.5 | 93.9 | 90.7 | 87.8 | 85.0 | 82.4 | 79.9 | 77.4 | 75.1 | 72.3 | 69.4 | 66.7 | 64.0 |
| 8 | 92.2 | 89.2 | 86.3 | 83.7 | 81.1 | 78.6 | 76.2 | 73.9 | 70.7 | 68.0 | 65.3 | 62.6 |
| 7.5 | 90.7 | 87.8 | 85.0 | 82.4 | 79.9 | 77.4 | 75.1 | 72.3 | 69.4 | 66.7 | 64.0 | 61.3 |
| 7 | 89.2 | 86.3 | 83.7 | 81.1 | 78.6 | 76.2 | 73.9 | 70.7 | 68.0 | 65.3 | 62.6 | 59.9 |
| 6.5 | 87.8 | 85.0 | 82.4 | 79.9 | 77.4 | 75.1 | 72.3 | 69.4 | 66.7 | 64.0 | 61.3 | 58.6 |
Columns are reps, cells are % of one rep max. Your e1RM = weight ÷ (cell ÷ 100). To plan a set, multiply your e1RM by the cell for the reps and RPE you want.
Plates and bars
A standard Olympic bar weighs 20 kg (45 lb in pound gyms); women's bars are 15 kg and technique bars 10 kg or 15 lb. Competition collars add 2.5 kg each. The plate calculator finds the closest weight you can load with the plates you have, using the fewest plates, and shows what goes on each side. Plates are drawn in the usual competition colours (25 kg red, 20 blue, 15 yellow, 10 green); colours in your gym may differ.
Estimates for healthy adults who already lift. They're least reliable above 10 reps and for beginners. Warm up, use good form, and use a spotter or safety bars for heavy sets.
Common questions
What is a one rep max (1RM)?
Your one rep max is the heaviest weight you can lift once with good form for a given exercise. Lifters use it to set training weights as a percentage, such as 80% of 1RM for sets of about 8. You don't have to test it: a calculator estimates it from a hard set, so 100 kg for 5 reps gives about 116.7 kg by the Epley formula.
How accurate is a one rep max calculator?
Estimates are closest for sets of about 1 to 10 reps taken close to failure. Past 10 reps the formulas spread apart and people differ a lot, so the guess gets rougher. Even for 100 kg × 5 reps the seven formulas on this page range from 112.5 to 119 kg. Treat the result as a training guide, not an exact number.
What is the Epley formula?
The Epley formula estimates your one rep max as weight × (1 + reps ÷ 30). For 100 kg lifted 5 times that is 100 × (1 + 5 ÷ 30) = 116.7 kg. It is the most widely used 1RM formula and the default here. Brzycki, weight × 36 ÷ (37 − reps), gives a little less for the same set: 112.5 kg.
What does RPE mean in lifting?
RPE is the rate of perceived exertion on a 1 to 10 scale. RPE 10 means you had no reps left, RPE 9 means one more was possible and RPE 8 means two. A commonly used RPE chart turns reps and RPE into a percentage of 1RM: 5 reps at RPE 8 is 81.1%, so a 100 kg set points to about 123.3 kg.
What percentage of my 1RM should I train at?
Common guidance is 85 to 100% for 1 to 5 reps when training for strength, about 67 to 85% for 6 to 12 reps for muscle growth, and 50 to 67% for 12 reps or more for muscular endurance. These ranges overlap and are rules of thumb; any rep range builds some strength and muscle if the sets are hard enough.
Is it safe to test a true one rep max?
Max attempts carry more risk than normal sets, so warm up well, use good form, and have a spotter or safety bars, especially on bench press and squat. Many lifters prefer to estimate their max from a set of 3 to 5 reps instead, which is what this calculator does.
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