Epley Formula 1RM Calculator
Plug in any working set and get your one-rep max from the Epley formula, the equation behind most gym rep charts and fitness apps. Results show in kg or lb, with Brzycki alongside as a cross-check and a training percentage chart for your next block.
| % of 1RM | Weight | Typical Reps |
|---|---|---|
| 100% | 114.5 kg | 1 rep (your max) |
| 95% | 109 kg | 2 reps |
| 90% | 103 kg | 3-4 reps |
| 85% | 97.5 kg | 5-6 reps |
| 80% | 91.5 kg | 7-8 reps |
| 75% | 86 kg | 9-10 reps |
| 70% | 80 kg | 10-12 reps |
| 65% | 74.5 kg | 12-14 reps |
| 60% | 69 kg | 15+ reps |
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What Is the Epley Formula?
The Epley formula estimates your one-rep max (1RM) from a set of more than one rep: 1RM = weight × (1 + reps ÷ 30). Put simply, every rep you complete is treated as worth about 3.3% of your max on top of the weight on the bar. Five reps adds about 16.7%, ten reps adds 33.3%.
It comes from Boyd Epley, the strength coach at the University of Nebraska who built one of the first full-time college strength programs and went on to help found the NSCA. He published the equation in 1985 in his training material for Husker athletes. Because it is simple enough to run in your head between sets, it spread into nearly every gym chart, spreadsheet, and app that followed.
One detail worth knowing: taken literally, the formula says a single at 100 kg means a 103.3 kg max, which makes no sense. This calculator, like most, treats a 1 rep set as your actual 1RM and only applies the equation from 2 reps up.
Epley Formula Worked Example in kg
Say you squat 100 kg for 5 clean reps. Divide 5 by 30 to get 0.167, add 1 to get 1.167, then multiply by 100. Your Epley estimate is 116.7 kg, or about 257 lb.
Run the same set through Brzycki and you get 100 × 36 ÷ (37 - 5) = 112.5 kg. That gap of about 4 kg is typical in the 3 to 8 rep range, where Epley reads a little more optimistic. Push the set to 10 reps at 100 kg and the two formulas land on the same number, 133.3 kg. Past 10 reps, Brzycki climbs faster and Epley becomes the more conservative of the two.
That crossing point is the key to reading Epley: slightly high on low-rep sets, level with Brzycki at 10, slightly low at 11 and 12. Here is how it stacks up against the other common equations, each run on the same 100 kg × 5 set.
Epley vs Brzycki, Lombardi, O'Conner, Wathan and Lander
- Epley (1985): 1RM = w × (1 + r ÷ 30). 116.7 kg. Linear, so each added rep adds the same amount. Slightly generous under 10 reps.
- Brzycki (1993): 1RM = w × 36 ÷ (37 - r). 112.5 kg. Lower than Epley under 10 reps, equal at 10, higher above. Often the closer fit for sets of 3 to 8.
- Lombardi: 1RM = w × r^0.10. 117.5 kg at 5 reps but only 125.9 kg at 10, so it flattens out and reads low on higher-rep sets compared with Epley.
- O'Conner: 1RM = w × (1 + 0.025 × r). 112.5 kg. The most conservative linear option, about 8 kg under Epley on a set of 10 (125 kg vs 133.3 kg).
- Wathan: 1RM = 100 × w ÷ (48.8 + 53.8 × e^(-0.075 × r)). 116.6 kg, almost identical to Epley at 5 reps and slightly higher at 10 (134.7 kg).
- Lander: 1RM = 100 × w ÷ (101.3 - 2.67123 × r). 113.7 kg, between Brzycki and Epley at 5 reps, and 134.1 kg at 10.
Epley Accuracy by Rep Range
Every rep-max formula gets less reliable the further your set drifts from a true single. Here is how much weight to put on an Epley estimate depending on the set you feed it.
- 1 to 5 reps: the tightest range. Studies comparing prediction equations usually find estimates within about 2 to 4% of a tested max here, and the formulas barely disagree with each other. A hard set of 3 to 5 is the best input you can give the calculator.
- 6 to 10 reps: still useful, but expect error closer to 5% for many lifters. Epley reads a touch high compared with Brzycki in this band, and the gap between the two cards in the calculator is a good picture of that uncertainty.
- 11 to 12 reps: muscular endurance starts to drive the result more than max strength. Some lifters can do 15 reps at 70% and others stall at 9. The calculator stops at 12 because past that point the number says more about your conditioning than your 1RM.
- Your training history: lifters who live in high-rep work can squeeze out more reps at a given percentage, so Epley tends to overestimate their max. Powerlifters who mostly train triples often get fewer reps at the same percentage, so a set of 10 tends to undershoot them.
Using Your Epley Estimate for Percentage-Based Programming
Treat the Epley number as a training reference, not a meet total. Many coaches set a training max at 90% of the estimated 1RM for programs like 5/3/1. That buffer absorbs bad sleep and rough days and keeps every working set moving with good bar speed.
Using the 116.7 kg estimate from the example above, a 90% training max is 105 kg. A week that calls for 5 reps at 75% puts 78.75 kg on the bar, which you can load exactly with 1.25 kg plates or round to 80 kg. In pounds, the same training max is about 231 lb.
Re-run the calculator every 3 to 4 weeks from a hard top set instead of testing a true max. If the Epley estimate climbs while your working sets feel the same, the program is doing its job. If it stalls for a full block, that is your cue to change something, not to test harder.
Why This Calculator Shows Brzycki Too
Epley is the focus of this page, and you can read the pure Epley result straight from its card in the calculator. The tool also shows Brzycki and the average of both because no single equation fits every lifter. When the two agree within a kilo or two, you can trust the estimate. When they spread apart, which happens as reps move away from 10, that spread tells you how much uncertainty the set carries.
For day-to-day programming, the average is a sensible middle ground. It trims some of Epley's optimism on low-rep sets without leaning fully on Brzycki's steeper curve at 11 and 12 reps.
Epley Formula FAQ
Is the Epley formula accurate?
For sets of 1 to 10 reps it usually lands within about 2 to 5% of a tested max, which is plenty for setting training weights. It gets less reliable past 10 to 12 reps, on sets that were not close to failure, and for lifters whose rep endurance is unusually high or low.
Epley vs Brzycki, which is better?
Neither wins everywhere. Brzycki is often slightly closer in the 3 to 8 rep range, where Epley tends to read a little high. The two match exactly at 10 reps, and above that Epley is the more conservative. Averaging both, as this calculator does, is a practical compromise.
What is the Epley formula for 1RM?
1RM = weight × (1 + reps ÷ 30). For 100 kg × 5 reps: 100 × (1 + 5 ÷ 30) = 116.7 kg, about 257 lb. A single rep counts as your 1RM, so the formula only applies from 2 reps up.
How many reps should I use with the Epley formula?
A hard set of 3 to 6 reps taken close to failure gives the most reliable estimate. Sets of 7 to 10 still work but carry more error, and anything past 12 reps reflects endurance more than strength.
Does the Epley formula work for deadlift?
Yes, with a caveat. Grip, lower back fatigue, and resetting between reps mean many lifters lose reps on the deadlift faster than on squat or bench, so a set of 8 or more can mislead. Keep deadlift estimates to sets of 2 to 5 and use the deadlift calculator for lift-specific standards.
Why do calculators give different 1RMs?
Each formula was fit to a different group of lifters and models fatigue across reps a little differently. Epley is linear, Brzycki curves upward, Lombardi flattens out. At low reps they agree closely, at higher reps they drift apart, which is why two calculators can disagree by 5 kg or more on a set of 10.
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