One Rep Max Calculator (1RM)
Enter the weight you lift and how many reps you can do with it to see your estimated one rep max (1RM), plus a chart of the weight for every rep count from 1 to 20.
Weight for each number of reps
| Reps | Weight (lb) | % of 1RM |
|---|---|---|
| 1 | — | — |
| 2 | — | — |
| 3 | — | — |
| 4 | — | — |
| 5 | — | — |
| 6 | — | — |
| 7 | — | — |
| 8 | — | — |
| 9 | — | — |
| 10 | — | — |
| 11 | — | — |
| 12 | — | — |
| 13 | — | — |
| 14 | — | — |
| 15 | — | — |
| 16 | — | — |
| 17 | — | — |
| 18 | — | — |
| 19 | — | — |
| 20 | — | — |
In gray, 13 to 20 reps: the formulas lose accuracy and the figure is only a rough guide.
Plates from 45 lb to 2.5 lb per side, not counting collars.
Results are estimates. Solvemis accepts no responsibility for the results obtained or for how they are used. Always double-check the result and talk to a qualified professional before making decisions.
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How it works
How to use it
- Pick an exercise and a recent set you took close to failure.
- Enter the weight in pounds (or kilograms, one tap away) and the number of reps (1 to 20; 10 or fewer works best).
- Read your estimated 1RM and what each formula gives.
- Use the chart to see the weight for each number of reps.
How it is calculated
The 1RM is the average of Epley's (1985) formula, weight × (1 + reps / 30), and Brzycki's (1993), weight × 36 / (37 − reps). With one rep, the 1RM is the weight itself. The chart applies both formulas in reverse for each rep count and rounds to 1 lb (or 0.5 kg). For the plates (under the 1RM and in the chart), it takes the nearest weight you can load on the chosen bar, with plates from 45 to 2.5 lb or from 25 to 1.25 kg (those in the IPF technical rules), per side from heaviest to lightest, not counting collars. You can pick another formula to match your app (Epley, Brzycki, Wathen 1994 or Mayhew et al. 1992), and the chart uses the same one. The exercise doesn't change the calculation; for the deadlift, the formulas tend to fall short (LeSuer et al., 1997).
Sources
- Strength Testing: Predicting a One-Rep Max from Reps-to-Fatigue (Brzycki, 1993) — Journal of Physical Education, Recreation & Dance
- The Accuracy of Prediction Equations for Estimating 1-RM Performance in the Bench Press, Squat, and Deadlift (LeSuer et al., 1997) — Journal of Strength and Conditioning Research
- IPF Technical Rulebook (2026), 2.3 Bars and discs — International Powerlifting Federation (IPF)
- Relative Muscular Endurance Performance as a Predictor of Bench Press Strength in College Men and Women (Mayhew et al., 1992) — Journal of Applied Sport Science Research
- A Weight-Dependent 1RM Prediction Equation Optimized on 303,494 Near-Failure Sets Across 388 Exercises (2026, preprint; Wathen, 1994) — arXiv
About this calculator
Your max without the risk
Testing the heaviest weight you can lift once (1RM) is demanding and carries some risk. That’s why it is usually estimated from a set with more reps: if you lift 175 lb for 10 reps, your 1RM is around 233 lb. For a good estimate, use a set taken close to failure, one where you couldn’t have done one or two more reps.
The rep chart
For your 1RM, the chart gives the weight you could lift for each number of reps and what percentage of your max it is. Many strength programs work like that: “4 sets of 6 at 85%”. Your rep count is highlighted, and the bar shows the percentage.
Why it gets less accurate with more reps
The formulas work well up to about 10 reps. Beyond that, each person’s endurance and form on the last reps come into play: two people with the same 1RM can do 15 or 25 reps with the same weight. That’s why rows 13 to 20 are gray and, above 20 reps, the calculator gives no result. It also varies with the exercise: people tend to do more reps at the same percentage in the squat and deadlift than in the bench press.
The two formulas
| Reps | Epley | Brzycki |
|---|---|---|
| 3 | 110% | 106% |
| 5 | 117% | 113% |
| 10 | 133% | 133% |
| 15 | 150% | 164% |
(Estimated 1RM as a percentage of the weight lifted.) They agree at 10 reps; above that they drift further apart, which is exactly the least reliable zone.
Train smart
It is an estimate for planning your training, not a record. Warm up before heavy sets, use a spotter or safety bars, and if you are new or have an injury, check with a coach or a healthcare professional.
Frequently asked questions
What is a one rep max?
It is the heaviest weight you can lift once with good form in an exercise. Many strength programs use it as a reference and set loads as a percentage of your 1RM.
How accurate is it?
It is an estimate. With sets of up to about 10 reps it usually lands close to the real max; with more reps the error grows, which is why those rows are gray. It also depends on the exercise and the person: someone with more endurance does more reps at the same percentage.
Which formula does it use?
The average of two widely used formulas: Epley (weight × (1 + reps / 30)) and Brzycki (weight × 36 / (37 − reps)). They agree at 10 reps; below that Epley gives a little more, and above it, less.
Should I test my real 1RM?
You don't need to in order to train: the estimate is enough to work out loads. If you test it, warm up well, use a spotter or safety bars, and check with a coach if you are new or have an injury.
Updated October 19, 2026
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