Enter the weight you lifted and how many reps you got. We run all seven standard formulas and show you the range, not one confident number.
Estimated one-rep max
median of seven formulas — the full range is 253 to 268 lb
Lowest of the seven253 lb
Highest of the seven268 lb
Your set was86% of max
Every one-rep-max formula applied to this set
Formula
Equation
Estimate
Brzycki
w x 36 / (37 - r)
253 lb
O'Conner
w x (1 + r / 40)
253 lb
Lander
100w / (101.3 - 2.67123r)
256 lb
Wathan
100w / (48.8 + 53.8e^-0.075r)
262 lb
Epley
w x (1 + r / 30)
263 lb
Lombardi
w x r^0.10
264 lb
Mayhew
100w / (52.2 + 41.9e^-0.055r)
268 lb
Fitted on sets of 2 to 10 reps. Above 10 the estimates drift apart and none of them is dependable.
This calculator needs JavaScript to recalculate. The answer shown above was worked out when the page was built and is correct for the date in the address bar.
A one-rep max estimate exists so you can programme the rest of your training without testing a true max every time. Almost every strength programme is written as a percentage of 1RM: five sets of three at 80%, back-off sets at 65%, a heavy single at 92%. You need a working figure to turn those percentages into plates. You do not need that figure to be exact, and it cannot be.
Worked example: 225 lb for 5 reps
Formula
Equation
Estimate
Brzycki
w × 36 ÷ (37 − r)
253 lb
O'Conner
w × (1 + r ÷ 40)
253 lb
Lander
100w ÷ (101.3 − 2.67123r)
256 lb
Wathan
100w ÷ (48.8 + 53.8e−0.075r)
262 lb
Epley
w × (1 + r ÷ 30)
263 lb
Lombardi
w × r0.10
264 lb
Mayhew
100w ÷ (52.2 + 41.9e−0.055r)
268 lb
Median 262 lb. Spread 15 lb, about 6%. In plates that is the difference between two 45s plus a 25 a side and adding a further 10. The honest answer is “somewhere around 260”. Any calculator that prints a single number to the pound is telling you something the underlying maths does not support — which is exactly why this page prints all seven.
Which formula to trust
Brzycki is the most conservative at low rep counts and the most commonly used in coaching. Epley runs higher and pulls further away as reps climb. Wathan and Mayhew were fitted on bench-press data specifically and tend to sit in the middle. At 2 to 5 reps all seven agree within a few percent and the choice barely matters. At 8 to 10 reps they diverge by 10% or more, and that divergence is the useful information: it is telling you the estimate is getting soft.
We report the median of all seven rather than picking one, because no published comparison has established a clear winner across lifts, populations and rep ranges, and the median is robust to any single formula being a poor fit for you.
Methodology
Seven published one-rep-max equations — Epley (1985), Brzycki (1993), Lombardi (1989), O'Conner (1989), Wathan (1994), Lander (1985) and Mayhew (1992). All were derived by regression from submaximal and maximal lifts performed by trained lifters, mostly in college athletic populations, between the 1970s and the 1990s. This page computes all seven and reports the median as the headline figure.
Limitations, stated plainly
These formulas were fitted on sets of roughly 2 to 10 reps. Above 10 reps every one of them drifts, and not in a consistent direction, so the spread widens and the median stops meaning much. They also assume the set was taken close to failure with clean technique — five reps that moved fast and five that were a grind produce the same input and very different truths. Bigger, more experienced lifters tend to hold a higher percentage of their max for a given rep count than the regressions predict, so a strong lifter is often under-estimated.
Treat the output as a starting point for programming, never as a number to attempt cold. Warm up properly and use a spotter or safety bars.
This is a fitness estimate, not medical advice, and not a substitute for a professional who can actually see you.
Common questions
Which one-rep max formula is the most accurate?
There is no single winner. Brzycki is more conservative at low rep counts, Epley more generous as reps climb, and Wathan and Mayhew were fitted on bench-press data specifically. Published comparisons disagree with each other, largely because they used different lifts and different populations. That is why this page reports the median of all seven — a median is robust to any one formula being a poor fit for you, and the spread between them tells you how much confidence the estimate deserves.
Why do different websites give me different one-rep maxes?
Because they are using different equations and not telling you which. From 225 lb for 5 reps, the seven standard formulas return anywhere from 253 to 268 lb. A site that has picked Epley will always read higher than one that has picked Brzycki, and neither is wrong. It is a 6% disagreement at 5 reps and considerably worse at 10.
Why does the estimate get less reliable at higher reps?
The relationship between reps and percentage of max is not linear, and it varies far more between people at high rep counts than at low ones. At 3 reps almost everyone is somewhere near 93% of their max. At 12 reps the real figure might be 65% or 75% depending on your muscle-fibre make-up, your conditioning and how honest your definition of failure is. The formulas fit an average that fewer and fewer people match. This is why we cap our pre-built pages at 10 reps.
Is it safe to actually test my one-rep max?
Testing a true max is a normal part of strength training for experienced lifters, and it is also where most gym injuries happen. If you are going to do it: warm up thoroughly, work up in small jumps, use a spotter or set safety bars at a height that lets you fail safely, and stop when technique breaks rather than when the weight stops moving. If you are new to the lift, use the estimate and train instead. Nothing on this page is a recommendation to attempt a maximal lift.
Does this work the same for deadlifts as for bench press?
Not quite. Deadlift rep sets degrade faster than bench sets, because grip, lower back and general systemic fatigue arrive before the prime movers give out. A 10-rep deadlift set therefore tends to under-estimate your true single relative to what the formulas predict. Squats sit in between. The formulas were mostly fitted on bench press data, so treat bench estimates as the most reliable and deadlift estimates as the loosest.
Should I enter my best set or an average set?
Your best recent set, taken close to failure, with technique you would be happy to show a coach. An easy set of five under-states you; a set with two grinding reps and a bounced rep over-states you. If your last set of five felt like you had three more in the tank, the estimate below is meaningfully low.