What is the Epley formula for 1RM?

The Epley (1985) formula is 1RM = w × (1 + r ÷ 30), where w is the weight lifted and r is the number of reps performed. For a single rep it returns the lifted weight exactly. For a set of 5 at 100 kg it predicts 100 × (1 + 5/30) = 116.7 kg.

How accurate is the Epley 1RM estimate?

Research shows all single-set 1RM prediction formulas have a mean error of roughly ±5–10 % compared with an actual tested maximum. Accuracy is highest when reps are kept between 2 and 10; sets above 10 reps introduce more variability because fatigue and technique breakdown have a larger effect. Use the estimate as a planning guide, not a certified maximum.

Which formula is most accurate — Epley, Brzycki or Lander?

No formula wins universally. Epley and Brzycki give almost identical results for low-rep sets (2–6) and are the most cited in peer-reviewed strength research. Brzycki tends to be slightly more conservative at high rep counts (>10). Lander and Mayhew were validated on different populations. The comparison bar chart on this page shows all five formulas side by side so you can see how much they diverge for your specific lift.

Should I test my 1RM directly or use a prediction formula?

A direct 1RM test is more precise but requires a proper warm-up, a spotter and carries injury risk. Predicted 1RMs let you programme percentages safely without attempting true maximal loads every training cycle — most powerlifting and weightlifting programmes use predicted 1RMs for daily work sets and only test actual maxima at competitions or every 8–12 weeks.

What do the training zones in the loading table mean?

Maximal (90–100 % 1RM) targets absolute strength with very low reps (1–4). Strength (80–89 %) builds maximal force at 4–8 reps. Hypertrophy (70–79 %) drives muscle growth at 8–12 reps. Endurance (60–69 %) develops muscular endurance at 15–20 reps. Most strength programmes rotate through these zones in a periodised block structure.

Can I use this for bench press, squat and deadlift?

Yes — the formulas are lift-agnostic. They were originally validated on the bench press but are routinely applied to squat, deadlift, overhead press and most other barbell movements. Accuracy may be slightly lower for technical lifts (e.g. Olympic lifts) where skill and technique limit the rep count independently of muscular strength.

Epley 1RM Calculator

The Epley 1RM calculator lets you predict your one-rep maximum (1RM) from a submaximal effort — meaning you never have to attempt a potentially risky single maximum lift just to set your training percentages. Enter the weight you moved and how many reps you completed, and the tool instantly returns your estimated 1RM along with a complete training-load table covering every standard intensity zone from 60 % to 100 %.

The calculator supports five peer-reviewed formulas — Epley (1985), Brzycki (1993), Lander (1985), Lombardi (1989) and Mayhew et al. (1992) — displayed side by side in a live comparison bar chart so you can see how much the estimates diverge for your specific lift. Two additional solve-for modes let you work the formula in reverse: find the exact bar load for a prescribed set given a target 1RM, or predict how many reps you should hit at any given weight.

How it works

The original Epley formula published in 1985 is:

1RM = w × (1 + r ÷ 30)

where w is the weight lifted (kg or lb) and r is the number of reps completed. The derivation assumes a linear relationship between the load lifted and the rep count, with the coefficient 1/30 ≈ 0.033 representing the fractional strength loss per additional repetition. When r = 1 the formula collapses to 1RM = w, which is trivially correct.

The Brzycki formula (1993) uses a slightly different model:

1RM = w × 36 ÷ (37 − r)

This gives nearly identical results for low-rep sets but diverges at higher rep counts (above 10), where Brzycki is generally considered more conservative and slightly more accurate.

The remaining formulas each use different empirical constants derived from their validation populations:

Formula	Expression
Epley (1985)	w × (1 + r/30)
Brzycki (1993)	w × 36 / (37 − r)
Lander (1985)	(100 × w) / (101.3 − 2.67 × r)
Lombardi (1989)	w × r^0.10
Mayhew et al. (1992)	(100 × w) / (52.2 + 41.9 × e^(−0.055 × r))

For the solve-for-weight and solve-for-reps modes, each formula is algebraically inverted where a closed-form solution exists. Mayhew (which contains an exponential) is solved numerically by bisection over the range 1–36 reps.

Worked example

A lifter bench presses 100 kg for 5 reps. Applying the Epley formula:

1RM = 100 × (1 + 5 ÷ 30)
    = 100 × 1.1667
    = 116.7 kg

Their training load table then becomes:

% 1RM	Weight (kg)	Zone
100 %	116.7	Maximal
90 %	105.0	Maximal
85 %	99.2	Strength
80 %	93.3	Strength
75 %	87.5	Hypertrophy
70 %	81.7	Hypertrophy

Using solve-for-weight in reverse: to work at 80 % of a 120 kg target 1RM for 3 reps, the required bar load is 120 ÷ (1 + 3/30) = 120 ÷ 1.1 = 109.1 kg.

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