One Rep Max Calculator

Weight lifted, kg

Repetitions

Result

1RM (average)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 taxing, so most lifters estimate it from a set they already performed. The estimate is reliable up to about five reps and drifts upward beyond ten.

Epley and Brzycki are the two standard formulas and they differ by a few percent. Showing both makes the uncertainty visible rather than hiding it behind one confident-looking number.

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 accurate is an estimated 1RM?

Within a few percent for sets of 1–5 reps. Above ten reps the estimate depends more on your endurance than on maximal strength and becomes unreliable.

Should I test my actual max instead?

Rarely worth it. A true max attempt carries real injury risk and takes days to recover from; for programming, an estimate is entirely sufficient.

What are the percentages for?

Most strength programmes prescribe load as a share of 1RM — roughly 70% for volume, 80–85% for strength, 90%+ for peaking.

Why do the two formulas disagree?

They were fitted to different groups of lifters. Brzycki tends to read lower at higher reps; averaging them 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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