One Rep Max Calculator

Written byOleh Soloninupdated 25 September 2026

Weight lifted, kg

Repetitions

Result

One-rep max, kg

91.7

Epley formula93.3
Brzycki formula90
90% of 1RM82.5
80% of 1RM73.3
70% of 1RM64.2

This result is informational only and is not professional advice.

Two formulas, because they disagree

Estimate a one-rep max from a set you have actually completed, with Epley and Brzycki shown separately, plus training percentages.

Testing a true one-rep max is risky and draining, so it is estimated from a set you have already done. The estimate is tightest for sets of up to five reps: beyond that endurance plays a bigger part and the formulas drift apart — by more than 13 kg at 15 reps with 100 kg.

Epley and Brzycki are the two standard formulas, and they differ by a few percent. Showing both is more honest than hiding the uncertainty behind one confident number.

How to use

Enter the weight on the bar in kilograms.
Enter how many reps you managed in a set taken to or near failure — 1 to 20, most accurate up to five.
The result gives the 1RM by Epley, by Brzycki and their average.
Below it are working weights at 90, 80 and 70 percent of the 1RM for programming.

The same 100 kg for different reps

Epley: 1RM = weight × (1 + reps / 30). Brzycki: 1RM = weight × 36 / (37 − reps). For a single rep the calculator returns the weight itself, since that set was the one-rep max. Below ten reps Brzycki reads lower, at ten the two agree, and above ten Brzycki climbs faster — by fifteen reps the gap is 13.6 kg.

Every row comes from the calculator on this page.
Reps with 100 kg	Epley, kg	Brzycki, kg	Average, kg
1	100	100	100
2	106.7	102.9	104.8
3	110	105.9	107.9
5	116.7	112.5	114.6
8	126.7	124.1	125.4
10	133.3	133.3	133.3
12	140	144	142
15	150	163.6	156.8

Working weights from a 1RM

Percentage-based programmes set loads as a share of the one-rep max; which share, how many reps and how many sets is up to the programme. The calculator shows 90, 80 and 70 percent of the average of the two formulas — by the reversed Epley formula, about three, eight and thirteen reps to failure.

Every row comes from the calculator on this page, weights in kilograms.
Set	1RM, kg	90%	80%	70%
60 kg × 8	75.2	67.7	60.2	52.7
80 kg × 5	91.7	82.5	73.3	64.2
100 kg × 3	107.9	97.1	86.4	75.6
100 kg × 5	114.6	103.1	91.7	80.2
120 kg × 5	137.5	123.8	110	96.3
140 kg × 2	146.7	132	117.3	102.7

What this calculator shows

An estimated 1RM averaged from both formulas
The Epley and Brzycki figures separately
Working weights at 90%, 80% and 70% for programming

What to keep in mind

Accuracy is best at 1–5 reps; high-rep sets depend heavily on endurance rather than strength.
Assumes the set was taken close to failure with clean technique.

FAQs

How do I calculate a 1RM with the Epley formula?

Multiply the weight by (1 + reps / 30). 80 kg for 5 reps is 80 × 1.167 = 93.3 kg. Brzycki gives 80 × 36 / 32 = 90 kg for the same set, and the average is 91.7.

What is my max if I bench 100 kg for 5?

About 114.6 kg: 116.7 by Epley and 112.5 by Brzycki. If the same 100 kg goes for 3 reps, the estimate is 107.9 kg.

How accurate is an estimated 1RM?

Tightest for sets of 1–5 reps. Above ten reps the result says more about endurance, and the formulas diverge further.

Should I test my actual max instead?

For programming an estimate is usually enough. A true max attempt takes recovery and carries injury risk if technique slips, so it is worth doing deliberately rather than for the number.

What are the percentages for?

Percentage-based programmes prescribe load as a share of 1RM, and the programme decides which share. The calculator shows 70, 80 and 90 percent: for a 1RM of 91.7 kg that is 64.2, 73.3 and 82.5 kg.

Why do the two formulas disagree?

They were fitted to different groups of lifters and grow at different rates. Below ten reps Brzycki reads lower than Epley, at ten they match, above ten it reads higher. The average is a reasonable middle ground.

Worked example

Five reps at 80 kg

Input: 80 kg × 5

Output: About 92 kg (Epley 93.3, Brzycki 90)

Note: The two formulas differ by more than 3 kg here, which is a fair reminder that this is an estimate rather than a measurement.

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One Rep Max Calculator

Result

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