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One Rep Max Calculator

Enter a set you have already done and get your estimated 1RM, averaged across seven published formulas, with the percentage table and every rep max underneath it.

115.5 kg

Estimated one rep max, averaged across 7 formulas. Individually they range from 112.5 to 119 kg.

Formulas used

Every one of these is a curve fit to population averages, not a law. Averaging several is more reliable than picking a favorite. Untick any you do not want in the average.

  • 116.7
  • 112.5
  • 117.5
  • 119
  • 113.7
  • 112.5
  • 116.6

Want to keep this number? The One Rep Max app saves every calculation and charts it over time.

Download One Rep Max Calculator on the App StoreGet One Rep Max Calculator on Google Play

One rep max percentage chart

What to load for a set written as a percentage of your max.

PercentWeightTypical use
125%144.4Overload, partials, rack pulls
120%138.6
115%132.8
110%127.1
105%121.3
100%115.5One rep max
95%109.7Heavy single or double
90%104Sets of 2 to 3
85%98.2Sets of 4 to 5
80%92.4Sets of 6 to 8
75%86.6Sets of 8 to 10
70%80.9Sets of 10 to 12
65%75.1Warm ups and technique work
60%69.3
55%63.5Bar speed and recovery work
50%57.8

Rep max chart

The heaviest you should expect to manage for a given number of reps.

RepsWeight
2109
3105.7
4102.8
5100.1
697.5
795
892.6
990.4
1088.2
1186.1
1284.1

How the estimate is made

Every formula here takes the same two inputs, the weight on the bar and the reps you managed, and fits them to a curve drawn from population averages. None of them is a law of physics, and they disagree with each other by a few percent, which is the honest measure of how precise this can be.

Rather than pick a favorite, the calculator runs all seven and averages the results. Averaging cancels out the direction each one happens to lean. If you would rather use a single formula, untick the rest under Formulas used and the average follows your selection.

The two you will see quoted most often are Epley, 1RM = weight × (1 + reps ÷ 30), and Brzycki, 1RM = weight × 36 ÷ (37 − reps). Below about six reps they agree closely. Above ten they scatter, because rep performance starts to depend on conditioning and pain tolerance rather than pure strength.

Why the RPE question matters

Every one of these formulas assumes you took the set to failure. Almost nobody does, and a set of six you could have taken to eight is not the same set at all.

Rate of Perceived Exertion fixes that. The number is really a statement about reps in reserve: 10 means nothing left, 9 means one more rep was there, 8 means two, in half point steps. Tell the calculator how hard the set felt and it works from the reps you could have done rather than only the ones you did.

It moves the answer more than you would expect. 80 kg for 6 comes out at 95 kg as a true grinder at RPE 10, and 100 kg if you stopped with two in the tank at RPE 8. If you never train to failure and you ignore RPE, you have been underselling yourself by around five percent for years.

Which number should you train off?

Use the averaged figure, and treat it as a starting point rather than a verdict. Most programs are written as percentages of a max, so the table above is the part you will actually use week to week. 5/3/1, Smolov and 5×5 are all prescribed that way, and the barbell plate calculator turns any percentage into the plates to load on each side. If 85% does not feel like a five rep set when you get under it, trust the bar over the arithmetic and adjust the estimate down.

Keep whichever approach you choose fixed. The value is in comparing your own numbers over time, not in the absolute figure, and a consistent method beats an accurate one that changes every month.

Do you need to test a real max?

If you compete, yes. You need to know what happens under a genuine single, with the nerves and the commands and a third attempt you are not sure about.

Otherwise it is rarely worth the fatigue or the risk. An estimate off a heavy set of three to five gives you everything you need to program, costs nothing extra, and can be updated every session. Do that for a few months and the trend tells you far more than one tested single ever would. A tested max is one data point. A logged estimate is a graph.

There is more on the reasoning, the research history behind each formula and where they break down in our guide to how to calculate your one rep max.

Common questions

How accurate is a one rep max calculator?
Within a few percent for sets of three to six taken close to failure. Accuracy falls away above ten reps, where endurance starts to matter more than maximal strength. The spread between the seven formulas shown here is a fair estimate of the uncertainty.
Which one rep max formula is the most accurate?
None of them individually. They are all curve fits to population averages, and which one fits you best depends on your training history and fiber makeup. Averaging several is more reliable than picking a favorite, and staying consistent matters more than either.
What is the Epley formula?
1RM = weight × (1 + reps ÷ 30). A set of 100 kg for 5 reps gives 116.7 kg. Published by Boyd Epley in 1985, it is the one most often quoted, and it is linear, so it keeps climbing at a steady rate as the reps rise.
What is the Brzycki formula?
1RM = weight × 36 ÷ (37 − reps). A set of 100 kg for 5 reps gives 112.5 kg, about four kilos below Epley. Matt Brzycki published it in 1993. It is the most conservative of the seven at moderate rep counts, and it breaks down entirely at 37 reps, where the divisor reaches zero.
What is the Lombardi formula?
1RM = weight × reps^0.1. A set of 100 kg for 5 reps gives 117.5 kg. Lombardi published it in 1989. Being a power curve rather than a straight line, it flattens off at high rep counts instead of running away.
What is the Mayhew formula?
1RM = weight ÷ (0.522 + 0.419 × e^(−0.055 × reps)), where e is Euler's number, roughly 2.718. A set of 100 kg for 5 reps gives 119 kg, the highest of the seven. Mayhew and colleagues published it in 1992 from bench press data.
What is the McGlothin formula?
1RM = weight × 100 ÷ (101.3 − 2.67123 × reps). A set of 100 kg for 5 reps gives 113.7 kg. Published by McGlothin in 1984, it sits near the conservative end, between Brzycki and Wathan.
What is the O'Conner formula?
1RM = weight × (1 + 0.025 × reps). A set of 100 kg for 5 reps gives 112.5 kg. O'Conner published it in 1989. It is the simplest of the seven, adding a flat 2.5% per rep, which makes it easy to do in your head and increasingly optimistic past about ten reps.
What is the Wathan formula?
1RM = weight ÷ (0.488 + 0.538 × e^(−0.075 × reps)), again with e as Euler's number. A set of 100 kg for 5 reps gives 116.6 kg, almost identical to Epley at that rep count. Wathan published it in 1994, and it holds up better than the linear formulas at high reps.
How many reps give the most accurate estimate?
Three to six, taken close to failure. Much below that and you are nearly testing a max anyway; much above it and the prediction is closer to guesswork.
Does the calculator work in pounds?
Yes. The formulas are unit agnostic, so switch the toggle to lb and every number on the page, including the percentages and rep maxes, is in pounds.
How often should I recalculate my one rep max?
Any time you hit a set that felt notably strong. Because the estimate comes from ordinary working sets, you can update it every session without ever peaking or deloading for a test.

Keep the number, not just the answer

The One Rep Max app does everything on this page and remembers it. Log the set and it charts every lift over time, so you can see whether a max is still climbing or peaked in March. Free on iPhone and Android.

Download One Rep Max Calculator on the App StoreGet One Rep Max Calculator on Google Play