How the 1RM calculator works
A one-rep max, or 1RM, is the heaviest weight you can lift for one clean rep. Testing it takes a heavy single and a spotter. The calculator estimates it from a set you already did: the weight, and the reps you got before you could not do another.
The headline number uses the Epley formula
1RM = weight × (1 + reps ÷ 30). A set of 100 kg for 5 reps gives 116.7 kg. Each extra rep adds a thirtieth of the weight to the estimate. Trackist estimates your max in the app with the same formula, counting at most 12 reps.
A single is already a max, so 1 rep returns the weight itself. The Epley formula is meant for 2 reps or more.
It runs 7 formulas side by side
Rep-max formulas come from coaches’ charts and small studies, so they disagree. The calculator shows 7 widely used ones. In each, w is the weight and r the reps. For 100 kg × 5:
| Formula | Year | Equation | 100 kg × 5 |
|---|---|---|---|
| Epley | 1985 | w × (1 + r ÷ 30) | 116.7 kg |
| Brzycki | 1993 | w × 36 ÷ (37 − r) | 112.5 kg |
| Lander | 1985 | 100 × w ÷ (101.3 − 2.67123 × r) | 113.7 kg |
| Lombardi | 1989 | w × r^0.1 | 117.5 kg |
| Mayhew | 1992 | 100 × w ÷ (52.2 + 41.9 × e^(−0.055 × r)) | 119 kg |
| O’Conner | 1989 | w × (1 + r ÷ 40) | 112.5 kg |
| Wathen | 1994 | 100 × w ÷ (48.8 + 53.8 × e^(−0.075 × r)) | 116.6 kg |
At 10 reps, Epley and Brzycki give the same answer: 133.3 kg from 100 kg. Under 10 reps Brzycki reads lower, and over 10 it reads higher.
Past 10 reps, the formulas split
Up to 10 reps, the 7 formulas stay within 10 kg of each other on a 100 kg set. Past 10, the gap grows fast:
| Reps with 100 kg | Lowest to highest 1RM | Gap |
|---|---|---|
| 3 | 105.9 kg to 114 kg | 8.1 kg |
| 5 | 112.5 kg to 119 kg | 6.5 kg |
| 8 | 120 kg to 127.7 kg | 7.7 kg |
| 10 | 125 kg to 134.7 kg | 9.7 kg |
| 12 | 128.2 kg to 144.4 kg | 16.2 kg |
| 15 | 131.1 kg to 163.6 kg | 32.5 kg |
| 20 | 134.9 kg to 211.8 kg | 76.8 kg |
Studies find the same. Mayhew and colleagues (2008) saw the formulas work better under 10 reps to failure. Reynolds and colleagues (2006) predicted the 1RM best from a 5-rep max, and worse from 10 and 20. The calculator takes up to 20 reps and warns you past 10.
Let the app work out the weight
From your second session of an exercise, Trackist suggests what to try from your last session, in steps your gym can load: 2.5 kg on a barbell, 2 kg on dumbbells and 5 kg on a machine or cable.
Percentages of your one-rep max
Programs often write the weight as a share of your 1RM: 5 sets of 5 at 80% means 80 kg if your max is 100 kg. For a 1RM of 120 kg:
| % of 1RM | Weight |
|---|---|
| 100% | 120 kg |
| 95% | 114 kg |
| 90% | 108 kg |
| 85% | 102 kg |
| 80% | 96 kg |
| 75% | 90 kg |
| 70% | 84 kg |
| 65% | 78 kg |
| 60% | 72 kg |
| 55% | 66 kg |
| 50% | 60 kg |
The calculator above fills in this table from your own set.
How much you can lift for a number of reps
Run the Epley formula backwards and you get the weight for any number of reps: weight = 1RM ÷ (1 + reps ÷ 30). For a 1RM of 120 kg:
| Reps | Weight | % of 1RM |
|---|---|---|
| 1 | 120 kg | 100% |
| 2 | 112.5 kg | 93.8% |
| 3 | 109.1 kg | 90.9% |
| 4 | 105.9 kg | 88.2% |
| 5 | 102.9 kg | 85.7% |
| 6 | 100 kg | 83.3% |
| 7 | 97.3 kg | 81.1% |
| 8 | 94.7 kg | 78.9% |
| 9 | 92.3 kg | 76.9% |
| 10 | 90 kg | 75% |
| 11 | 87.8 kg | 73.2% |
| 12 | 85.7 kg | 71.4% |
This is why a set of 5 sits at about 85.7% of your max, and a set of 10 at 75%.
What the calculator cannot tell you
- Reps must be hard. The formulas assume you stopped because you could not do another rep. A set you ended with 3 reps left in the tank reads low.
- The formulas were written mostly from young, trained men on the bench press. LeSuer and colleagues (1997) tested 7 formulas on the bench press, squat and deadlift, and every one underestimated the deadlift.
- One set is one day. A good night’s sleep or a bad one moves the estimate.
- It says nothing about your health. If something hurts when you lift, the number is not worth chasing: read what to do when a lift hurts.
To see how your max compares with lifters of your sex and age, try the strength calculator. To raise it, add weight in small steps: progressive overload explains how.
FAQ
Questions, answered.
How do I calculate my one-rep max?
Take a hard set you finished, and use the Epley formula: 1RM = weight × (1 + reps ÷ 30). A set of 100 kg for 5 reps gives an estimated 1RM of 116.7 kg. A single is already your max, so 1 rep gives the weight itself.
Which 1RM formula is the most accurate?
No formula wins on every lift. LeSuer and colleagues (1997) tested 7 formulas on the bench press, squat and deadlift. Every estimate correlated closely with the tested max, but each formula underestimated the deadlift. Pick one formula and stick with it, so this month’s estimate compares with last month’s. Use a set of 10 reps or fewer.
How many reps should I use to estimate my 1RM?
A hard set of 3 to 10 reps. In Reynolds and colleagues’ 2006 study, a 5-rep max predicted the 1RM best. Past 10 reps the formulas drift apart: from a set of 100 kg × 20, they range from 134.9 kg to 211.8 kg.
Is the Epley or the Brzycki formula better?
They agree at 10 reps, where both turn 100 kg into 133.3 kg. Under 10 reps Brzycki gives a slightly lower estimate, and over 10 a higher one. Neither is more accurate on every lift.
What percentage of my 1RM can I lift for 5 reps?
About 85.7%, by the Epley formula. For 3 reps it is about 90.9%, for 8 reps 78.9% and for 10 reps 75%.
Does the 1RM calculator work in pounds?
Yes. Switch the units to pounds and type the weight in pounds. Every formula gives the same answer in either unit.
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