Which 1RM formula should I trust?

Neither alone. A blend is safer, and the gap between Epley and Brzycki is itself information - a wide gap means too many reps for a confident estimate.

Does a 1RM calculator work for bodyweight exercises?

Only if you can add load. Weighted pull-ups work; push-ups do not, because the resistance cannot be varied finely enough.

🏋️One-rep max (1RM) calculator

Q: Is it safe to test a true 1RM?

For an experienced lifter with a spotter, occasionally. For everyone else the estimate is better: it costs nothing, carries no injury risk and is accurate enough to programme from.

Q: Why did my estimated max drop?

Usually sleep, food or fatigue rather than lost strength. One bad session is noise; three in a row on the same lift is a plateau.

Estimate your one-rep max from any set, the average of the Epley and Brzycki formulas, plus your training loads.

Weight lifted (kg)

Reps

Estimated 1RM

0 kg

Training loads

How a one-rep max is estimated

You do not need to attempt a true single to know roughly what you could lift. The relationship between the weight you use and the reps you get with it is predictable enough that a set of five tells you most of what a max attempt would.

Two formulas dominate, and Musclory uses both:

Epley:   1RM = weight x (1 + reps / 30)
Brzycki: 1RM = weight x 36 / (37 - reps)

They agree almost exactly at 10 reps and diverge either side: Epley reads higher at low reps, Brzycki at high ones. Below about 10 reps both are reliable. Above 12 the estimate drifts, because endurance starts deciding the set instead of strength.

A worked example

100 kg for 5 reps:

Epley:   100 x (1 + 5/30)      = 116.7 kg
Brzycki: 100 x 36 / (37 - 5)   = 112.5 kg

So the honest answer is "somewhere around 113-117 kg", not a single decimal. Treat the range as the answer.

What it is actually for

Programmes prescribe load as a percentage of your max, so the estimate is what turns "3 sets of 5 at 80%" into a number on the bar. It is also the cleanest way to see progress: adding reps at the same weight raises your estimated max, which is real strength even though the plates did not change.

Use a set of 3-8 reps taken close to failure. A set with five reps left in the tank estimates a max you do not have.
Estimate per lift. Your squat and bench do not share a percentage.
Re-estimate every few weeks rather than chasing it every session.

Common questions

Is it safe to test a true 1RM?

For an experienced lifter with a spotter, yes, occasionally. For everyone else the estimate is better: it costs nothing, carries no injury risk and is accurate enough to programme from.

Which formula should I trust?

Neither alone. Musclory shows a blend, and the gap between the two is itself information - a wide gap means you used too many reps for a confident estimate.

Does it work for bodyweight exercises?

Only if you can add load. Pull-ups with a belt work; push-ups do not, because the resistance cannot be varied finely enough for the relationship to hold.

Why did my estimate drop?

Usually sleep, food or accumulated fatigue rather than lost strength. One bad session is noise; three in a row on the same lift is a plateau worth acting on.

Sources

Epley B. "Poundage Chart", Boyd Epley Workout, 1985. Brzycki M. "Strength testing: predicting a one-rep max from reps to fatigue." JOPERD, 1993.

Track it in Musclory, free

Estimates for general fitness guidance, not medical advice.