One rep max calculator

Epley and Brzycki estimates, in kg or lb. Updated 9 November 2026.

Enter the weight you lifted and how many reps you completed. The calculator returns an estimated one rep max (1RM) from two common formulas, Epley and Brzycki, and a table of loads from 95% down to 60% of that estimate.

How the estimate works

Both formulas take the weight you lifted and the reps you completed, and scale the weight up to the load you could lift for one rep.

For 2 or more reps, use the formulas as written. For 1 rep this calculator returns the weight you lifted, which is also what Brzycki's formula gives. Epley's formula applied to 1 rep gives 3.3% more, and RepMark shows that raw value. For 100 kg × 5 reps, Epley gives 100 × (1 + 5 ÷ 30) = 116.7 kg and Brzycki gives 100 × 36 ÷ 32 = 112.5 kg. From 2 to 9 reps Epley is higher than Brzycki, the two are equal at 10 reps, and above 10 Brzycki is higher. Brzycki stops working at 37 reps, where the divisor reaches zero.

Epley's formula is credited to Boyd Epley (1985). Brzycki's was published by Matt Brzycki in 1993 as "Strength Testing—Predicting a One-Rep Max from Reps-to-Fatigue".

The percentage table multiplies each estimate by 95%, 90% and so on down to 60%, then rounds to the nearest 2.5 kg or 5 lb. 80% of the unrounded Epley estimate for that set (116.67 kg) is 93.3 kg, which rounds to 92.5 kg.

When the estimate is rough

Above about 10 reps the estimate is a ballpark. At that length a set is limited by endurance, breathing and grip as much as by strength, and the two formulas move apart. For a closer number, use a heavy set of 2 to 5 reps.

The result also depends on the set. If you stopped with several reps left, the estimate comes out low. If your technique changed during the set, it can come out high. Different lifts and different people drop off at different rates, so the same formula can overshoot on one lift and undershoot on another. Use the result to plan loads. It does not prove what you can lift for a single.

Questions

What is a one rep max?

A one rep max (1RM) is the heaviest weight you can lift for a single repetition of an exercise with the technique you normally use. A calculator estimates it from a lighter set so you do not have to attempt a max single.

How do you calculate a one rep max from reps?

Enter the weight and the number of reps you completed. The Epley formula multiplies the weight by (1 + reps ÷ 30). The Brzycki formula multiplies the weight by 36 ÷ (37 − reps). For 100 kg for 5 reps, Epley gives 116.7 kg and Brzycki gives 112.5 kg.

What is the difference between the Epley and Brzycki formulas?

Both turn a weight and a rep count into an estimate. From 2 to 9 reps Epley gives the higher number, the two match at 10 reps (both multiply the weight by 1.333), and above 10 reps Brzycki gives the higher number. For sets of 2 to 8 reps the two estimates are within about 4% of each other.

How accurate is a one rep max calculator?

It is an estimate. The formulas are rules of thumb, so your own max can land above or below the result. They are less reliable as reps go up, and rough above about 10 reps. A set stopped well short of failure also gives a low estimate.

Which set should I use to estimate my one rep max?

Use a hard set on the lift you want to estimate, taken close to the most reps you could do, with the same technique on every rep. A heavy set of 2 to 5 reps asks the formula to extrapolate the least.

How are the percentage loads calculated?

Each row multiplies the estimated 1RM by the percentage, from 95% down to 60% in steps of 5%, and rounds the load to the nearest 2.5 kg or 5 lb. The table shows one column for the Epley estimate and one for the Brzycki estimate.

Does RepMark use the Epley formula?

Yes. RepMark logs your sets by weight and reps and shows an Epley estimated 1RM for each loaded set and each exercise. It applies the formula as written to every set, so a single rep shows about 3% above the weight lifted, where this page returns the weight itself. The estimated 1RM trend chart is part of the optional Supporter purchase.

Does this page save or send my numbers?

No. The calculation runs in your browser with a few lines of JavaScript on this page, and nothing you type is sent or stored.

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