MultiConvers

One Rep Max Calculator

Estimate a one-rep max from a submaximal set. Epley is the headline figure (w × (1 + reps/30)); Brzycki sits beside it as a second published check. Reps are capped at 36. The page will not program your next cycle.

How to use

  1. Enter the weight you actually lifted — same units you use on the bar, not a converted “should have been.”
  2. Enter how many clean reps you completed. One rep is reported as that weight; reps above 36 are rejected.
  3. Read the Epley estimate as the primary 1RM. Compare Brzycki when you want a second regression.
  4. Do not walk into the gym and test that number because a website printed it. Not a training plan.

How it works

Epley says estimated 1RM = weight × (1 + reps/30). One hundred for five reps is 100 × (1 + 5/30) ≈ 116.7. Brzycki says weight × 36 / (37 − reps); at five reps that is 100 × 36 / 32 = 112.5. The two lines were fitted on different samples. They agree better at low reps and drift as the set gets long. This page shows both so you can see the spread; it does not average them.

A single completed rep is the weight itself. There is nothing to extrapolate. At 37 reps Brzycki’s denominator is zero, which is one reason the cap is 36. High-rep sets were never what these regressions were built for; a 20-rep “max” is a different quality than a heavy triple.

Neither formula sees depth, pause, bar path, spotter help, fatigue from earlier work, or whether the last rep was a grind. A sloppy five at 100 is not the same input as a crisp five. The algebra treats them identically.

This is not a percentage chart for 5×5 and not medical advice. Attempting a true max needs a plan, a spotter and a reason. Lean Body Mass and Calories Burned answer other questions; they do not estimate 1RM.

Units are whatever you typed. The output is in the same unit, to one decimal, because the equations produce a real number, not a plate combination. A worked check at the other end: 60 for 10 reps is Epley 60 × (1 + 10/30) = 80, Brzycki 60 × 36 / 27 = 80 exactly. At 12 reps the two diverge again (Epley 84, Brzycki 86.4). Use the spread as a reminder that a website 1RM is a band, not a plate to load.

Formula

Epley: 1RM = w × (1 + r/30)
Brzycki: 1RM = w × 36 / (37 − r)

Worked examples

  • Epley 100 × 5

    100 for 5 reps → about 116.7

Useful notes

  • Epley is the headline; Brzycki is a check, not an average.
  • Reps are limited to 1–36. Brzycki’s denominator hits zero at 37.
  • Not medical advice. Do not attempt a true max from a website number.

FAQ

Which formula is “correct”?

Neither is exact. Epley is the headline figure; Brzycki is a second published check.

Why cap reps at 36?

These equations were not built for very high-rep sets, and Brzycki’s denominator hits zero at 37.

Should I test that 1RM in the gym?

Only with a plan and a spotter. This page is arithmetic, not coaching.

Why do Epley and Brzycki disagree?

They are different published regressions. The gap usually widens as reps increase. This page does not pick a winner.

What if I only completed one rep?

The estimated 1RM is the weight you entered. There is no extrapolation from a single.

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