One Rep Max Calculator
Enter the weight you lifted and how many reps you got, and this estimates your one-rep max two different ways — plus the working weights for every rep range from that estimate.
Estimated one-rep max
114.6kg
- Epley
- 116.7 kg
- Brzycki
- 112.5 kg
- 1 reps
- 114.6 kg
- 2 reps
- 108.9 kg
- 3 reps
- 106.6 kg
- 4 reps
- 103.1 kg
- 5 reps
- 99.7 kg
- 6 reps
- 97.4 kg
- 8 reps
- 91.7 kg
- 10 reps
- 85.9 kg
- 12 reps
- 76.8 kg
- Both formulas are estimates from a single set, not a tested maximum. They agree closely at low reps and drift apart as reps rise.
- Reliable to about ten reps. Beyond that, endurance and technique matter more than strength and the estimate flatters you.
- Warm up properly and use a spotter before attempting anything near a true maximum.
About the one rep max calculator
A one-rep max is the most you can lift once with good form. Actually testing it is taxing, needs a spotter and is not something to do often, so lifters estimate it from a set they have already done and program from the estimate.
Two formulas dominate. Epley multiplies the weight by one plus reps divided by thirty; Brzycki divides by a term that shrinks as reps rise. They agree closely at low reps and drift apart as reps climb — at five reps they are within a per cent or two, at twelve they can differ noticeably.
Both are most reliable up to about ten reps. Past that you are measuring muscular endurance and technique as much as maximal strength, and the estimate starts flattering you. A set of twenty is not a useful basis for a one-rep prediction no matter which formula you use.
What it works out
- 1RM estimated by Epley and by Brzycki
- A percentage table from 1 to 12 reps
- Kilograms or pounds
- Any set from 1 to 20 reps
The formula
Epley: 1RM = w × (1 + r ÷ 30) Brzycki: 1RM = w × 36 ÷ (37 − r)
Epley scales the weight up by a fixed amount per rep — five reps adds a sixth to the weight, ten reps adds a third. It is simple and holds up well through the ranges most people train in.
Brzycki approaches it from the other direction, dividing by a term that grows as reps rise. At one rep both formulas return the weight itself, as they must. At five reps a hundred kilograms gives 116.7 by Epley and 112.5 by Brzycki — about a four per cent spread.
That spread is why both are shown. Neither is authoritative, and quoting one to a decimal place implies a precision that does not exist. The average of the two is a reasonable working figure, and the percentage table below it is what you would actually program from.
The percentages themselves are the standard chart: roughly 95% for a double, 87% for five, 80% for eight, 75% for ten. They are conventions built from experience rather than derived from the formulas, and individuals vary — some people grind out far more reps at a given percentage than others.
- w
- The weight lifted for the set.
- r
- Reps completed, to near failure with good form.
- 1RM
- The estimated maximum for a single repetition.
A worked example
A hundred kilograms lifted for five clean reps.
That works out to 114.6 kg.
- Epley
- 116.7 kg
- Brzycki
- 112.5 kg
- 1 reps
- 114.6 kg
- 2 reps
- 108.9 kg
- 3 reps
- 106.6 kg
- 4 reps
- 103.1 kg
- 5 reps
- 99.7 kg
- 6 reps
- 97.4 kg
- 8 reps
- 91.7 kg
- 10 reps
- 85.9 kg
- 12 reps
- 76.8 kg
Questions
How accurate is a one-rep max estimate?
Good to within a few per cent for sets of one to five, less reliable as reps climb. It is an estimate from a formula, not a measurement, so treat it as a programming tool rather than a number to chase.
Which formula should I use?
Either. Epley and Brzycki agree closely at low reps and differ by a few per cent higher up. Using the average of the two, as shown here, avoids arguing about which is right.
How many reps should I use for the estimate?
Three to five is the sweet spot — heavy enough to reflect maximal strength, light enough to be safe. Above ten reps you are largely measuring endurance and the estimate becomes optimistic.
Should I actually test my one-rep max?
Rarely, if at all. It is fatiguing, carries more injury risk than normal training, and needs a spotter and proper warm-up. Most people are better served by estimating from working sets and progressing the weight over time.
Why do the percentages differ from my experience?
Because the standard chart is an average. Some lifters manage many more reps at a given percentage than others, often depending on the lift and on fibre type. Adjust the chart to what you actually do rather than the other way round.
Does this work for every lift?
It works best on compound barbell lifts — squat, bench, deadlift, press — where the pattern is stable and the load is limited by strength. Isolation work and machine exercises fit the formulas less well.