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One Rep Max Calculator
Estimate a one rep max from a set you have actually done.
One Rep Max Calculator tool
Fewer reps gives a better estimate.
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Estimated 1RM
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Epley
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Brzycki
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Spread across formulas
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5-rep working weight
| Percentage of 1RM | Weight | Reps you should manage |
|---|
Estimates are most accurate from sets of 10 reps or fewer. Above that the relationship between reps and load varies too much between people and between lifts for any formula to be reliable.
About the One Rep Max Calculator
One Rep Max Calculator estimates the heaviest single lift you could manage, from a set you have already completed. That is safer and more practical than testing a true maximum, which needs warm-up, a spotter and a day when nothing else is planned.
Four formulas are shown because they disagree, and the spread is the useful information. Epley and Brzycki are the two most used and agree closely at low rep counts, diverging as reps rise. A set of three gives a tight estimate; a set of twelve gives a much looser one, which is why estimates from sets of ten or fewer are the ones worth trusting.
The percentage table is what the estimate is actually for. Training programmes are written in percentages of one rep max -- five sets of five at 85 per cent, say -- so the table converts the estimate into working weights and shows roughly how many reps each percentage should allow. Those rep figures are population averages, and individuals vary: some people grind out far more reps at 80 per cent than others.
This is general information and not medical advice. The formula cannot know your medical history, your medication, your body composition or anything else specific to you. Speak to a doctor or another qualified professional about any question concerning your health, and never delay seeking advice because of a figure on this page.
Your measurements are processed inside your own browser. Height, weight, age and anything else you enter never leave your device, nothing is logged, and nothing survives closing the tab.
Looking for something this does not cover? FreeToolsZone.org is more free browser-based tools, organised by job, and it is worth a look if one rep max calculator is only part of what you are working on.
How to use the One Rep Max Calculator
- Choose formula and unitsThe fields below change to match what you pick, so only the figures that matter to your case are asked for.
- Enter weight lifted and repetitions completedDecimals are fine, and thousands separators are accepted and ignored.
- Read the estimated 1rm, epley and brzyckiThe figures update as you type. The Calculate button is there if you would rather press something, but nothing waits for it.
- Copy or check the resultCopy the summary with the copy button, or open the table to check it row by row.
Features
- Shows estimated 1rm, epley, brzycki, spread across formulas and 5-rep working weight together, so you are not running it twice
- A results table you can read across
- Updates as you type, with no button to press and no page reload
- Copy the result in one click
- Free, no sign-up, and it runs entirely in your browser
Who uses this tool
The one rep max calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:
- Estimating a max without testing one
- Converting a one rep max into training percentages
- Tracking strength progress between programme blocks
- Comparing what the common formulas predict
Frequently asked questions
How many reps give the best estimate?
Between three and eight. Below three and fatigue has little effect to measure; above ten the relationship varies too much between people.
Which formula should I use?
Epley or Brzycki. They agree at low reps and are the two most widely used. The spread figure tells you how much confidence the rep count justifies.
Does it work for every lift?
Better for squats, bench press and deadlift than for isolation movements or anything technique-limited, where form fails before strength does.
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Checked and rebuilt on 2026-10-14. The method this calculator uses is described in the section above, and corrections go through the contact page.