Strength
One Rep Max Formula
Updated 1 Nov 2026 · Source: Epley, Brzycki and Lombardi formulas ↗
Enter a set to see what all seven classic one rep max formulas predict, side by side and sorted from highest to lowest.
Worked example
- Epley: 100 × (1 + 8 ÷ 30) = 126.7 lb
- Brzycki: 100 × 36 ÷ (37 − 8) = 124.1 lb
- Lombardi: 100 × 8^0.10 = 123.1 lb
- Average of the three: (126.7 + 124.1 + 123.1) ÷ 3 = 124.6, shown as 125 lb
Estimated max from a 100 lb set, by formula and reps
| Reps | Epley | Brzycki | Lombardi | Mayhew | O'Conner | Wathen | Lander |
|---|---|---|---|---|---|---|---|
| 2 | 106.7 | 102.9 | 107.2 | 111.4 | 105.0 | 105.1 | 104.2 |
| 3 | 110.0 | 105.9 | 111.6 | 114.0 | 107.5 | 109.0 | 107.2 |
| 5 | 116.7 | 112.5 | 117.5 | 119.0 | 112.5 | 116.6 | 113.7 |
| 8 | 126.7 | 124.1 | 123.1 | 126.3 | 120.0 | 127.7 | 125.1 |
| 10 | 133.3 | 133.3 | 125.9 | 130.9 | 125.0 | 134.7 | 134.1 |
| 12 | 140.0 | 144.0 | 128.2 | 135.4 | 130.0 | 141.5 | 144.4 |
| 15 | 150.0 | 163.6 | 131.1 | 141.7 | 137.5 | 150.9 | 163.3 |
The seven formulas
In each formula, w is the weight lifted and r is the number of reps completed. All of them were published between 1985 and 1994.
- Epley (1985): w × (1 + r ÷ 30). It began as a poundage chart in a college training manual, not a research paper.
- Lander (1985): 100 × w ÷ (101.3 − 2.67123 × r).
- O'Conner and colleagues (1989): w × (1 + 0.025 × r).
- Lombardi (1989): w × r raised to the power 0.10.
- Mayhew and colleagues (1992): 100 × w ÷ (52.2 + 41.9 × e to the power −0.055 × r), fitted on 435 college students in the bench press.
- Brzycki (1993): w × 36 ÷ (37 − r).
- Wathen (1994): 100 × w ÷ (48.8 + 53.8 × e to the power −0.075 × r), from a strength coaching textbook.
Why they disagree
The formulas have different shapes. Epley and O'Conner add a fixed share of the weight for every rep, Brzycki and Lander bend upward as reps climb, and Lombardi flattens out. Mayhew and Wathen use a curve that levels off at high reps.
At low reps the shapes stay close together. For 100 lb lifted 8 times they range from 120.0 lb (O'Conner) to 127.7 lb (Wathen). At 15 reps the gap grows to 131.1 lb (Lombardi) versus 163.6 lb (Brzycki).
What the studies found
A 1997 study tested seven equations on 67 untrained college students in the bench press, squat and deadlift. Predictions tracked real maxes closely (correlations above 0.95), yet every equation underestimated the deadlift.
Later work pointed the same way on rep range. A 2008 study of 103 women found the equations more accurate when sets had fewer than 10 reps, and a 2006 study found a 5 rep max gave the best prediction.
Which formula to use where
No single formula wins for every lift and lifter. Under about 10 reps most of them land within a few pounds of each other, so the choice matters less than the quality of the set. Above 10 reps, pick a heavier set rather than a different formula.
Epley and Brzycki meet at exactly 10 reps: 100 lb for 10 gives about 133 lb with both. Below 10 reps Epley runs slightly higher.
Why we average three
Our calculators report the mean of Epley, Brzycki and Lombardi. Brzycki tends to read low at moderate reps and Lombardi tends to read low at high reps, so the average softens the extremes of any one equation. Full details are on our method page and the papers are listed under sources.
Related pages
One Rep Max Calculator, Rep Max Chart, How Many Sets and Reps, RPE Calculator
Questions
Is it spelled Wathen or Wathan?
Wathen. The formula comes from a 1994 strength coaching textbook chapter; the spelling with an a is a common mistake.
What does Epley give for a single rep?
Taken literally, it adds 3.3% even at one rep. Most calculators, ours included, return the lifted weight when reps equal 1.
Which formula is the most accurate?
Studies have not found one that is best for every exercise. Using a set under 10 reps does more for accuracy than switching formulas.
Where can I use these formulas on my own sets?
The one rep max calculator runs all seven and shows the range next to our average.
How we calculate: every formula, with its author and year, is on our method page; data sources and their licenses are on sources.
gymnical.com gives estimates from published formulas and public data. It is not medical advice and not a training prescription. Last reviewed November 2026.