What is a one rep max (1RM)?
Your one rep max, or 1RM, is the heaviest weight you can lift once with good form. It is the standard way to describe strength in a lift, and most strength programs set their working weights as a percentage of it.
Testing a true 1RM is tiring and carries more risk than normal training, so most lifters estimate it from a heavier set of 2 to 10 reps instead. That is what the calculator above does.
How to calculate your 1RM
The calculator uses two of the most widely used formulas, which work best for sets of 10 reps or fewer, and shows the average of the two:
| Formula | Calculation | Best for |
|---|---|---|
| Epley | weight × (1 + reps / 30) | Sets of 4 to 10 reps |
| Brzycki | weight × 36 / (37 - reps) | Sets of 2 to 6 reps |
Example: you bench press 100 kg for 5 reps. Epley gives 116.7 kg and Brzycki gives 112.5 kg, so your estimated 1RM is about 114.5 kg.
- Pick a recent hard setUse a set you took close to failure, ideally 3 to 6 reps. The closer to a true max effort, the better the estimate.
- Enter the weight and repsCount only clean reps. A rep with a bounce, a half lockout or a spotter's help does not count.
- Use the percentagesRead the chart under the result to find your working weights, for example 75 % for sets of 8 to 10.
1RM percentage chart: how many reps at each percentage
Most lifters can do roughly the following number of reps at each percentage of their 1RM. Use it to choose weights for a program, or to check whether a set was as hard as it should be.
| % of 1RM | Typical reps | Training effect |
|---|---|---|
| 100 % | 1 | Max strength, testing |
| 95 % | 2 | Max strength |
| 90 % | 3 to 4 | Strength |
| 85 % | 5 to 6 | Strength |
| 80 % | 7 to 8 | Strength and muscle growth |
| 75 % | 9 to 10 | Muscle growth |
| 70 % | 11 to 12 | Muscle growth |
| 65 % | 13 to 15 | Muscle growth, technique |
| 60 % | 16 to 20 | Endurance, warm up sets |
These are averages. People with more endurance, or lifts that use more muscle mass like the squat, often get more reps at a given percentage than the chart shows.
How accurate is an estimated 1RM?
From a set of 2 to 6 reps, the estimate usually lands within a few percent of a tested max. The error grows with higher reps, because fatigue and conditioning start to matter more than strength. That is why the calculator warns you above 10 reps.
- Beginners often get a high estimate, because they cannot yet use all their strength in a single rep.
- Squats and deadlifts tend to allow more reps at the same percentage than presses.
- Sets taken to true failure give better estimates than sets that stopped with two reps left. If you rate effort by reps in reserve, the RPE calculator adjusts for the reps you had left.
How to use your 1RM in training
Percentage based programs like Wendler 5/3/1 set every working weight from your max. A common setup for muscle growth is 3 to 4 sets at 70 to 80 % of your 1RM, and for strength 3 to 5 sets at 80 to 90 %. Linear beginner programs like StrongLifts 5x5 skip percentages and add weight every session instead.
You do not need to retest your max to get stronger. Add a little weight or one more rep at the same weight, session after session. That is progressive overload, and it is the reason your 1RM goes up.
Want a lift specific number? The bench press calculator shows how your bench compares, and the bench press standards show what counts as a good bench for your bodyweight. For the lower body, see the squat standards and deadlift standards.
Gripp estimates your 1RM after every set
Log your sets and Gripp keeps your estimated max for every exercise up to date, shows it as a chart over time, and tells you what to lift next session to keep it climbing.
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