One Rep Max Calculator
Estimate your 1RM from a set of 1 to 20 reps with Epley, Brzycki, Lombardi and four more formulas, then get a percentage chart, rep maxes and plate loads.
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About this toolWhat is the One Rep Max Calculator?
The One Rep Max Calculator estimates the heaviest weight you could lift once from a set you have already done. Enter the weight and the number of clean reps and the page runs seven published equations, Epley, Brzycki, Lombardi, O'Conner, Lander, Mayhew and Wathan, shows each result, and averages them into one working estimate.
From that estimate it builds the two tables most programmes need: loads at 50 to 100% of your 1RM, rounded to the nearest loadable weight with the plates for each side of the bar, and a rep max table showing roughly what you could manage for 1 to 12 reps. Switch between kilograms and pounds, and change the bar weight if you use a 15 kg or 35 lb bar.
It all runs in your browser. There is nothing to sign up for and nothing is uploaded.
- Seven published 1RM formulas with their equations shown
- Average, lowest and highest estimate
- Percentage of 1RM chart from 50 to 100%
- Rep max table for 1 to 12 reps
- Plates per side for kg or lb bars
- Copy a text summary or a link with your numbers
How to use the One Rep Max Calculator
- Choose kg or lb.
- Enter the weight you lifted and how many full reps you completed with good form.
- Optionally change the bar weight from the default 20 kg or 45 lb for the plate column.
- Read the average 1RM, the lowest and highest formula, and the per-formula table.
- Use the percentage table to set training loads and the rep max table to choose weights for a given rep target.
Worked examples
100 kg for 5 reps
Input
100 kg × 5
Output
Estimated 1RM 115.5 kg (formulas range 112.5 to 119.0 kg)
Epley gives 116.7, Brzycki and O'Conner 112.5, Mayhew 119.0. Eighty per cent of 115.5 is 92.4 kg, which rounds to 92.5 kg: 25 + 10 + 1.25 kg per side on a 20 kg bar.
Bench press in pounds
Input
225 lb × 8
Output
Estimated 1RM 280.6 lb (formulas range 270.0 to 287.3 lb)
At 8 reps the spread is 17 lb, about 6%. The average is a sensible working number; a first attempt at 270 lb on test day would be cautious.
High-rep set
Input
60 kg × 15
Output
Formulas range from 78.7 kg (Lombardi) to 98.2 kg (Brzycki)
A 20 kg spread shows why the page warns above 10 reps. Retest with a heavier set of 3 to 6 reps for a usable number.
Background and insight
Testing a true single is slow and carries some risk, so coaches have estimated it from heavier multi-rep sets for decades. Boyd Epley, the first strength coach at the University of Nebraska, published w × (1 + r / 30) in 1985. Matt Brzycki's 1993 equation, w × 36 / (37 − r), gives exactly the same answer at 10 reps and a slightly lower one below that. Lombardi (w × r^0.1) and O'Conner (w × (1 + 0.025 r)) are more conservative, while Mayhew and Wathan use exponential curves fitted to college athletes and tend to come out higher.
All of them assume the set was taken to, or within one rep of, failure. The errors grow with the number of reps. Between 1 and about 6 reps, the formulas usually sit within 3% of each other; at 15 reps they can disagree by 25%, because endurance, technique and fibre type start to dominate. Brzycki in particular breaks down past about 10 reps and becomes undefined at 37.
The rep max table inverts the Epley and Brzycki equations and averages them. It lands close to the well-known reference that 5 reps is about 87% of maximum and 10 reps about 75%. Plate maths uses standard plates (25, 20, 15, 10, 5, 2.5 and 1.25 kg, or 45, 35, 25, 10, 5 and 2.5 lb) and works greedily from the heaviest.
Common use cases
Programming percentage-based training
Set loads for 5/3/1, Texas Method or any plan written as percentages of 1RM without testing a single.
Tracking strength without maxing out
Log the estimated 1RM from your top set each week to see progress safely.
Choosing weights for a rep target
Use the rep max table to pick a starting load for sets of 8 or 12.
Loading the bar quickly
Read the plates per side for every percentage instead of doing the sums between sets.
Tips and limitations
- Only count reps that met your normal standard of depth and lockout. Grinding out a rep with bad form inflates the estimate.
- Sets of 3 to 6 reps give the most reliable estimate. Above 10 reps treat the result as a rough guide.
- Estimates for squat and deadlift are often less accurate than for bench press, because fatigue builds faster in big lower-body lifts.
- Use a training max of about 90% of the estimate for programmes that ask for one.
- If you test a true single, work up in 3 to 5 jumps after a thorough warm-up, with a spotter or safety bars.
Frequently asked questions
Which one rep max formula is most accurate?
Studies disagree, and accuracy depends on the lift and the lifter. Epley and Brzycki are the most used and agree closely below 10 reps. Averaging several formulas, as this page does, smooths out the quirks of any single one.
How do I calculate my 1RM by hand?
With Epley: weight × (1 + reps / 30). For 100 kg × 5: 100 × (1 + 5 / 30) = 116.7 kg. With Brzycki: weight × 36 / (37 − reps) = 100 × 36 / 32 = 112.5 kg.
What percentage of my 1RM should I train at?
Common ranges are 85 to 100% for maximal strength (1 to 5 reps), 67 to 85% for hypertrophy (6 to 12 reps) and below 67% for muscular endurance. Beginners progress well on 70 to 80% loads.
How many reps can I do at 80% of my max?
Most people manage about 7 to 8 reps at 80%. The rep max table here puts 8 reps at about 80% of 1RM. Trained powerlifters often get fewer, endurance athletes more.
Is it safe to test a real one rep max?
For healthy, experienced lifters with good technique, a spotter and safety bars, it is reasonably safe. Beginners gain little from it and are better served by estimates from sets of 3 to 6.
Why do the formulas disagree so much at high reps?
They were fitted to different groups over different rep ranges. Past about 10 reps, local muscular endurance and pacing affect how many reps you get more than maximum strength does, so each curve extrapolates differently.
Is there an in-depth guide to the One Rep Max Calculator?
Yes. “Training Numbers Explained: Pace, Heart Rate Zones, 1RM and METs” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
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