How to use it
- Type the Weight lifted and choose kg or lb.
- Enter the number of Reps you completed, from 1 to 12. Above 10, the calculator notes "Estimates get less reliable above 10 reps".
- Read the Epley and Brzycki estimates, their average and the range across seven formulas. Below are the 50% to 95% table, a rep max table for 1 to 12 reps and the formula comparison.
- Keep the result with Copy link, Save image or Share.
How the calculation works
Both formulas turn a set of several reps into an estimated single-rep maximum (1RM). Here w is the weight lifted and r the number of reps.
Epley: 1RM = w × (1 + r ÷ 30). Each rep adds one thirtieth of the weight. It comes from a poundage chart by Boyd Epley in a 1985 training manual, not from a peer-reviewed study.
Brzycki: 1RM = w × 36 ÷ (37 − r). It was published in 1993 in the Journal of Physical Education, Recreation & Dance. It is often written as w ÷ (1.0278 − 0.0278 × r), which is the same curve with rounded numbers.
With one rep, both give the weight itself: the calculator skips the extra thirtieth that Epley's straight line would add. The average shown is simply (Epley + Brzycki) ÷ 2.
| Formula | 100 kg × 5 | 225 lb × 5 |
|---|---|---|
| Epley: w × (1 + 5 ÷ 30) | 116.7 kg | 262.5 lb |
| Brzycki: w × 36 ÷ 32 | 112.5 kg | 253.1 lb |
| Average | 114.6 kg | 257.8 lb |
How accurate is this?
Every formula is fitted on groups of lifters, so your own 1RM can differ. The seven formulas never agree exactly: with 100 kg they are closest at 5 to 7 reps (a 6.5 kg spread) and furthest apart at 12 reps (16.2 kg). At 1 rep they all give the weight itself. The one rep max formula comparison shows every rep count.
Ribeiro and colleagues (2024, International Journal of Strength and Conditioning) tested nine equations on 119 young men and women before and after training. No single equation won everywhere: Lombardi was closest for men on the bench press and squat, Brzycki and Lander for women on those lifts, and all equations missed for men on the arm curl. That is why this page shows the spread instead of one "right" number.
| Formula | Equation | 1RM |
|---|---|---|
| Epley | w × (1 + r ÷ 30) | 116.7 kg |
| Brzycki | w × 36 ÷ (37 − r) | 112.5 kg |
| Lander | w ÷ (1.013 − 0.0267123 × r) | 113.7 kg |
| Lombardi | w × r0.1 | 117.5 kg |
| Mayhew et al. | w ÷ (0.522 + 0.419 × e−0.055 r) | 119.0 kg |
| O’Conner et al. | w × (1 + 0.025 × r) | 112.5 kg |
| Wathen | w ÷ (0.488 + 0.538 × e−0.075 r) | 116.6 kg |
Where the two formulas differ
Epley grows in a straight line: every extra rep adds the same amount. Brzycki curves upward, because the gap (37 − r) shrinks as reps rise, and it would head toward infinity as reps approach 37.
So the two cross. Below 10 reps Epley reads higher (at 5 reps, 116.7 against 112.5 kg on a 100 kg lift). At exactly 10 reps both give 133.3 kg. Above 10, Brzycki reads higher, and at 12 reps it is 4.0 kg ahead. Showing both makes the difference visible instead of hiding it in one number.
What the studies found
A 2010 study in Motricidade compared six equations with a tested bench press 1RM in 31 male recreational lifters doing 4 to 10 reps. None differed significantly from the test. Epley's standard error was 2.9 kg and Brzycki's 3.1 kg.
Ribeiro and colleagues (2024) found that the best equation depended on the lift and on sex; details are under "How accurate is this?" above.
Both studies used sets that stay within roughly 10 reps. Past that there is little testing to lean on, which is why the calculator flags sets above 10.
Limits of 1RM estimates
The formulas assume the set was taken close to failure with steady technique. A set stopped well short of failure gives a low estimate.
They were checked mostly on young adults and on a few barbell lifts. Results may differ for other exercises, machines and age groups, since one equation may not fit every movement.
Reading the percentage table
The table lists 50% to 95% of the estimate. It is plain multiplication: on an estimate of 114.6 kg, 80% works out to 91.7 kg.
Strength work pairs with what you eat. The protein calculator shows the published daily reference amounts for your weight.
Questions
- Which is more accurate, Epley or Brzycki?
- In the studies above, neither clearly wins across all lifts. In one bench press study, their errors were 2.9 kg and 3.1 kg. Seeing both, plus the average, shows how wide the estimate really is.
- Why is the limit 12 reps?
- The studies behind these formulas mostly used sets of about 10 reps or fewer, and the seven formulas spread furthest at 11 and 12 reps. Above 12 the estimate says more about the formula than about you.
- What counts as a rep?
- A full repetition with your normal range of motion and technique. The formulas only know the count, so a short rep counts the same as a full one.
- Does it matter if I use kg or lb?
- No. Both formulas only multiply the weight, so the result comes out in the unit you entered. 100 kg × 5 gives 116.7 kg by Epley; 225 lb × 5 gives 262.5 lb.
- Do the formulas work for the deadlift?
- The studies cited on this page tested the bench press, squat and arm curl, not the deadlift. A deadlift estimate is the same arithmetic, but no study here checked it, so treat it with extra caution.
- What is a rep max table?
- It turns the estimate around: with a 1RM of 114.6 kg, it shows roughly what you could lift for 1, 2, 3 … 12 reps. Each row reverses Epley and Brzycki and averages them.