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One Rep Max Calculator
Enter a weight and the reps you got — we'll estimate your 1RM and show what you can lift at every rep range.
Runs entirely in your browser.
Estimated one-rep max
What you can lift
| Reps | % of 1RM | Weight |
|---|
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Get the free appWhat is a one-rep max?
Your one-rep max (1RM) is the most weight you can lift for a single rep of an exercise. It's the standard way to measure strength and to set training weights — most programs prescribe loads as a percentage of 1RM. You don't have to actually test it: this calculator estimates your 1RM from a set you've already done, which is safer and just as useful for programming.
The formulas we use
We average three well-established equations rather than trusting one. Epley: 1RM = w × (1 + reps/30). Brzycki: 1RM = w × 36 / (37 − reps). Lombardi: 1RM = w × reps^0.10. They agree closely at low reps and diverge as reps climb, so averaging them smooths out each one's bias. The rep-max table below works in reverse — it shows the weight you should be able to hit for each rep count based on your estimated max.
Frequently asked questions
How do you calculate one-rep max?
Enter a weight and how many reps you got with it. The calculator estimates your one-rep max (1RM) by averaging three established formulas — Epley, Brzycki and Lombardi — which is more reliable than relying on any single one. The estimate is most accurate at 1–10 reps; above that, fatigue makes it less precise.
How accurate is a 1RM calculator?
Very accurate in the 2–5 rep range, where most strength training happens. Below that you are basically testing a true max; above 10 reps endurance starts to dominate and the estimate drifts high. For 5x5 training, your 5-rep working weight gives a clean, reliable 1RM estimate.
What is a good one-rep max?
It depends on your bodyweight, gender, and the lift. Rather than a single number, use bodyweight ratios: an intermediate male lifter benches around 1x bodyweight and squats 1.5x for a 1RM. Use our strength standards calculator to see your level from beginner to elite.
Should I actually test my 1RM?
Rarely. On a beginner program like 5x5 you make faster progress training with 5 reps than maxing out, and true 1-rep attempts carry more injury risk. Estimating your 1RM from your working sets gives you the number without the downside.