Estimate Your One-Rep Max: Epley, Brzycki and Their Limits

The Epley and Brzycki formulas

Both formulas take the weight you lifted (w) and the number of reps you completed (r), and both assume the set was taken to or very near failure.

Epley: 1RM = w × (1 + r ÷ 30)Adds about 3.3% of the weight for every rep.

Brzycki: 1RM = w × 36 ÷ (37 − r)Grows faster as the reps rise, and cannot be used at 37 reps or more.

Worked example: you lift 80 kg for 5 reps. Epley gives 80 × (1 + 5 ÷ 30) = 80 × 1.1667 = 93.3 kg. Brzycki gives 80 × 36 ÷ 32 = 90.0 kg. A gap of about 3 kg is normal, so it is sensible to quote the result as a range, here roughly 90 to 93 kg.

A higher-rep set widens that gap. For 60 kg lifted 12 times, Epley gives 60 × (1 + 12 ÷ 30) = 84.0 kg, while Brzycki gives 60 × 36 ÷ 25 = 86.4 kg, already a difference of 2.4 kg from a lighter lift.

How to take a useful test set

The estimate is only as good as the set behind it. A practical routine looks like this:

1. Warm up with lighter sets, then pick a working weight you expect to lift for roughly 3 to 8 reps.
2. Perform the set with the same technique and range of motion you would use for a single, and count only clean reps.
3. Stop when the next rep would break form, and note the reps and the weight.
4. Rest for several minutes before any further heavy work.

If you stopped before you had to, a common adjustment is to add the reps you had left in reserve. Worked example: you lift 80 kg for 5 clean reps and judge that you could have done 2 more. Treat it as 7 reps: Epley gives 80 × (1 + 7 ÷ 30) = 98.7 kg, noticeably higher than the 93.3 kg from the 5-rep version. Judging reps in reserve takes practice, so the estimate is least certain for beginners.

How the two formulas compare

Here is what each formula says for a 100 kg lift at different rep counts:

Two things stand out. At one rep, Epley reports 103.3 kg for a lift of 100 kg, so it is meant for sets of two or more. And the formulas agree at 10 reps, then pull apart quickly: by 15 reps they differ by more than 13 kg.

Turning a max into training weights

Once you have an estimate, programmes usually work in percentages of it. Using a 90 kg estimate and rounding to the nearest 2.5 kg plate jump:

You can also run the formula backwards. If your estimated max is 90 kg and you want a set of 8, Epley suggests 90 ÷ (1 + 8 ÷ 30) = 71.1 kg, so a 70 kg or 72.5 kg bar is a sensible choice. For other percentages, the percentage calculator does the multiplication.

When the estimate is unreliable

• High reps. Beyond roughly 10 reps, endurance and pacing matter as much as strength, and formulas drift apart. Use sets of 3 to 8 where you can.
• Stopping short of failure. If you finished a set with reps left in reserve, the real max is higher than the formula says.
• Different lifts behave differently. The same percentage of 1RM allows more reps on some exercises than others, so a formula tuned on one lift may misjudge another.
• Form changes. Reps with a bounced bar or a shortened range of motion inflate the estimate.
• Daily variation. Sleep, food and stress all move your numbers, so one estimate is a snapshot, not a fixed value.

Use the same exercise, the same rep range and similar conditions each time you re-estimate, and compare like with like. For a quick answer from your own weight and reps, try the 1-rep max calculator.

This is general information, not coaching or medical advice. Lift heavy only with sound technique and a spotter or safety bars, and speak to a qualified coach or doctor if you are new to training or returning from injury.