Why is Brzycki considered the most accurate?

In several validation studies its predictions sat closest to tested 1RMs for sets of 2 to 10 reps, especially on the bench press and squat. The advantage is small — a percent or two over Epley — and disappears at very low reps where all formulas nearly agree.

What happens near 37 reps?

The denominator (37 − reps) approaches zero, so the estimate shoots toward infinity and then turns negative past 37. The formula is only meaningful well below that; this calculator blocks 37+ reps and suggests Epley or a lower-rep set instead.

For sets of 1 to 10 reps, Brzycki. For higher-rep sets, neither is great, but Epley degrades more gracefully. The honest answer is to estimate from a hard set of 3 to 6 reps, where the choice barely matters.

Does it work for every lift?

Best for compound barbell lifts — squat, bench, deadlift, press, row. For isolation moves and anything limited by balance or technique, a 'max' is more skill than strength and the estimate drifts.

How often should I re-test?

Every 4 to 8 weeks, or whenever a working set feels clearly lighter than last time. Percentage-based programmes assume the 1RM is current; a stale number makes every prescribed load too light.

Brzycki 1RM Calculator — One Rep Max From Reps

Training loads from your estimated 1RM
% of 1RM	Load	Typical reps
100%	—	1
95%	—	2
90%	—	3–4
85%	—	5–6
80%	—	7–8
75%	—	9–10
70%	—	11–12

The Brzycki formula

1RM = w × 36 ÷ (37 − reps), where w is the weight lifted and reps the number completed. Best suited to ≤ 10 reps.

Worked example

You squat 100 kg for 10 clean reps. Brzycki: 100 × 36 ÷ (37 − 10) = 3600 ÷ 27 = 133.3 kg. From an easier 100 kg × 5 it would read 100 × 36 ÷ 32 = 112.5 kg.

How it compares

At 5 reps Brzycki (112.5) and Epley (116.7) are about 4% apart; at 10 reps they converge near 133 kg. Above 12 reps Brzycki climbs faster and, by design, blows up as reps approach 37 — so it is a low-rep tool. For sets past 10 reps prefer Wathan or Mayhew.

Which formula for which rep range

Formula	Best for
Brzycki	≤ 10 reps
Lombardi	any rep count, conservative
O'Conner	low reps; understates at high reps
Wathan	wide range, good at 10+ reps
Lander	≤ 10 reps
Mayhew	bench press, 10+ reps
Epley	1–10 reps

Rule of thumb: Brzycki, Lander and O'Conner for sets of 10 reps or fewer; Wathan and Mayhew when the set ran longer; Lombardi as a conservative all-rounder. The safest input is a hard set of 3 to 6 reps, where every formula nearly agrees.

The other 1RM formulas

Epley formula — the default, and the parent calculator.
Lombardi — 1RM = weight × reps^0.10. A power curve rather than a straight line — stays sane at high reps.
O'Conner — 1RM = weight × (1 + 0.025 × reps). The gentlest estimate — 2.5% added per rep.
Wathan — 1RM = 100w ÷ (48.8 + 53.8 × e^(−0.075 × reps)). An exponential fit that holds up well at higher reps.
Lander — 1RM = 100w ÷ (101.3 − 2.67123 × reps). Close to Brzycki in shape; undefined near 38 reps.
Mayhew — 1RM = 100w ÷ (52.2 + 41.9 × e^(−0.055 × reps)). Derived from bench-press data; a solid pick for higher reps.

Using the number

Once you have a 1RM, programmes prescribe work as a percentage of it — use the table above the fold to plan a session. Feed your bodyweight and goal into the calorie calculator and macro calculator to support the training, and see progressive overload for adding weight over time.

Source: Brzycki, 1993; see Wikipedia, "One-repetition maximum".

Last reviewed: September 2026. Figures and formulas are checked against their published sources; see the site's data notes.

Brzycki One Rep Max Calculator

The Brzycki formula

Worked example

How it compares

Which formula for which rep range

The other 1RM formulas

Using the number

Related calculators

Related guides

Frequently asked questions