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One Rep Max Calculator

Enter a set you have done — the weight and how many reps — to estimate your one-rep max and see suggested loads for different rep ranges.

The formulas

Both were fitted to lifting data in the 1990s. They estimate the load you could handle for a single rep given that you managed a known number of reps with a lighter weight. The fewer reps in the input set, the more reliable the estimate.

Worked example

You bench press 100 kg for 5 clean reps. Epley: 100 × (1 + 5 ÷ 30) = 116.7 kg. Brzycki: 100 × 36 ÷ (37 − 5) = 112.5 kg. Call it about 115 kg. Your hypertrophy work at 70% would then be roughly 80 kg, and a heavy triple at 90% about 104 kg.

Reps ↔ percentage of 1RM

% of 1RMReps you can usually getTypical use
100%1Testing / peaking
90%3–4Max strength
80%7–8Strength / hypertrophy
70%11–12Hypertrophy
65%13–15Volume / endurance

Using the percentages

Once you have a 1RM, strength programmes prescribe work as a percentage of it. Re-estimate every 4 to 8 weeks as you get stronger, and use the load table above the fold to plan a session. See progressive overload for how to add weight over time.

Related tools

Frequently asked questions

What is a one-rep max?
The heaviest weight you can lift for a single clean repetition of an exercise. It is the reference point strength programmes use to set training loads as a percentage.
How accurate are 1RM estimates?
Good within about 5 to 8 reps of a true max — usually within a few percent. Accuracy drops fast above 10 reps because muscular endurance, not maximal strength, becomes the limiting factor. Estimate from a set of 3 to 6 reps for the best result.
Epley or Brzycki — which should I use?
They agree closely at low reps and diverge as reps rise. Epley tends to read slightly higher above 10 reps; Brzycki becomes unstable near 37 reps by design. For typical strength work either is fine — this tool shows both.
Is it safe to test my actual 1RM?
Only with a thorough warm-up, a spotter or safety pins, and real experience with the lift. For most people, estimating from a solid 3 to 5 rep set is safer and precise enough for programming. Beginners should skip max testing entirely for the first several months.
Does the estimate work for every exercise?
It works best for compound barbell lifts — squat, bench press, deadlift, overhead press, rows. It is less reliable for isolation moves and for movements limited by balance or technique rather than raw strength, where a 'max' is more about skill than muscle.
How often should I re-estimate?
Every 4 to 8 weeks, or whenever a working set feels clearly easier than the last time. Programmes that prescribe loads as a percentage of 1RM assume the number is current; a stale 1RM makes the percentages too light and slows progress.
My Epley and Brzycki numbers differ — which is right?
Neither is 'the' answer. At 1–5 reps they are within a percent or two. Above about 10 reps they drift apart (Epley reads higher) and both become rough, because you are testing muscular endurance more than maximal strength. Estimate from a low-rep set and take the average of the two.

Last reviewed: September 2026. Figures and formulas are checked against their published sources; see the site's data notes.