Why is Mayhew tied to the bench press?

Mayhew and colleagues (1992) built it from a large set of bench-press reps-to-fatigue tests, including the NFL combine's 225 lb bench test. The curve reflects how bench endurance specifically decays with reps, so it is most accurate there.

Can I use it for squats?

You can, but expect it to read slightly high — the squat usually allows more reps at a given percentage than the bench, and Mayhew's curve is calibrated to bench decay. Use Wathan or Lombardi for lower-body lifts.

Both are exponential and both handle high reps well. Mayhew is a touch more conservative and bench-specific; Wathan is the better all-round default. If they disagree by more than a few percent, your set was probably too long to estimate from.

Is there a pounds version?

The formula is unit-agnostic — put weight in kg or lb and the result comes back in the same unit. The 225 lb combine test is just the most famous application.

How many reps is too many for this?

Past about 15 reps even Mayhew is a rough guide, because you are testing conditioning. Use it to set an opening weight, then re-estimate from a set of 5 to 8.

Mayhew 1RM Calculator — One Rep Max (Bench Press Fit)

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 Mayhew formula

1RM = 100w ÷ (52.2 + 41.9 · e^(−0.055 · reps)), where w is the weight lifted and reps the number completed. Best suited to bench press, 10+ reps.

Worked example

Bench 100 kg for 10 reps. Mayhew: (100 × 100) ÷ (52.2 + 41.9 × e^(−0.55)) = 10000 ÷ 76.37 = 130.9 kg. For 100 kg × 5: 10000 ÷ (52.2 + 41.9 × e^(−0.275)) = 10000 ÷ 84.02 ≈ 119.0 kg.

How it compares

Mayhew sits a little below Wathan across most rep counts (about 131 vs 135 kg at 10 reps) and well above the linear formulas at high reps. It is the natural choice for the bench press, where it was validated — for the squat and deadlift, Wathan or Lombardi is a better match.

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.
Brzycki — 1RM = weight × 36 ÷ (37 − reps). The other standard; the most accurate of the set at low reps.
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.

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: Mayhew et al., 1992; see Wikipedia, "One-repetition maximum".

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

Mayhew One Rep Max Calculator

The Mayhew 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