What is a one-rep max?

Your one-rep max (1RM) is the heaviest weight you could lift for a single, full repetition of a given exercise with good form. It's the standard reference point for strength programming — most workout templates prescribe sets at 70–95 % of 1RM.

Why not just test my 1RM directly?

Testing a true 1RM cold is a bad idea. The lift takes a long warm-up, taxes the central nervous system, and the failure point is where injuries happen. Estimating from a sub-maximal set you can already do safely gives a working number without that risk.

Which formula should I use — Epley, Brzycki, or Lombardi?

They're three different empirical curves fit to lifter populations. Epley is roughly linear and tends to predict slightly higher than Brzycki at higher reps. Brzycki uses a hyperbolic form and reads a bit lower past 5 reps. Lombardi uses a power curve and is the most conservative across the range. In the 1–10 rep band the three usually agree within a few percent — try all three and average if you want a robust estimate.

How do I use the training-load percentages?

The percentages give you a working weight for different goals at a glance. Strength work commonly sits at 85–95 % of 1RM for low reps; hypertrophy is typically 70–85 % for moderate reps; speed and technique work runs lighter. Use the percentages as a starting point and adjust by feel — bar speed, form, and how the warm-ups moved should override the number on the bar.

How accurate is the estimate?

Within the 1–10 rep range, all three formulas typically land within ~5 % of a real tested 1RM for trained lifters. Above 10 reps the relationship between strength and endurance breaks down and the formulas systematically over-predict. Below 3 reps the numbers are very close to your tested max anyway.

HEAHealth & Fitness

One-Rep Max Calculator

Estimate your one-rep max (1RM) from a sub-maximal set. Pick Epley, Brzycki, or Lombardi, enter the weight you lifted and the reps you completed, and get your 1RM plus training-load percentages from 75 % to 95 %.

Units

Pick the weight unit you train with.

Formula

Three classic 1RM formulas. Try each — they agree within a few percent in the 1–10 rep range.

Weight lifted

Reps completed

Try an example

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How It Works

Formula

\text{1RM}_{\text{Epley}} = w \cdot \left(1 + \frac{r}{30}\right)

\text{1RM}_{\text{Brzycki}} = w \cdot \frac{36}{37 - r}

\text{1RM}_{\text{Lombardi}} = w \cdot r^{0.10}

Where

$w$: Weight lifted on the set(kg or lb)
$r$: Reps completed(reps)
$\text{1RM}$: Estimated one-rep maximum(kg or lb)

Enter the load you lifted, the number of clean reps you completed, and pick a formula. The calculator estimates the single-rep maximum that would have produced that set. From the 1RM we then derive five training-load percentages (95 / 90 / 85 / 80 / 75 %) so you can read a working weight off the same panel.

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