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 grey, 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 and rounds to 0.5 kg (or 1 lb). 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 25 to 1.25 kg (those in the IPF technical rules) or from 45 to 2.5 lb, 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, so it is usually estimated from a set with more reps: if you lift 80 kg for 10 reps, your 1RM is around 106.5 kg. Use a set taken close to failure.
The rep chart
For your 1RM, the chart gives the weight for each number of reps and its percentage of your max. Many programmes work like that: “4 sets of 6 at 85%”.
Why it gets less accurate with more reps
The formulas work well up to about 10 reps. Beyond that, endurance and form on the last reps come into play, so rows 13 to 20 are greyed out and, above 20 reps, there is no result. It also varies with the exercise.
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 and drift apart above it.
Train smart
It is an estimate for planning, not a record. Warm up, use a spotter or safety bars and, if you are new or injured, check with a coach or a health 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 programmes 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 greyed out.
Which formula does it use?
The average of Epley (weight × (1 + reps / 30)) and Brzycki (weight × 36 / (37 − reps)). They agree at 10 reps.
Should I test my real 1RM?
You don't need to in order to train. If you do, warm up well, use a spotter or safety bars, and check with a coach if you are new or injured.
Updated October 19, 2026
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