How to Use This Calculator
- Enter the weight you lifted, in kilograms or pounds.
- Enter how many reps you completed with good form, from 1 to 12.
- Click the button to see your estimated one rep max from two trusted formulas, plus a table of training weights at each percentage of that max.
This one rep max calculator estimates the heaviest weight you could lift once, based on a set you have already completed. Testing a true maximum carries real risk, especially for newer lifters, and it also drains you for days. Instead, an estimate from a normal training set gives you the same planning number, and it keeps the risk low. This page explains both formulas in plain words, and it then shows a worked example and a full percentage table.
How the One Rep Max Calculator Works
Two long-trusted formulas do the estimating, and each one reads your set in a slightly different way. First, the Epley formula multiplies your weight by one plus your reps divided by 30. In numbers, that is weight × (1 + reps/30). Next, the Brzycki formula multiplies your weight by 36 divided by (37 minus your reps). This one rep max calculator shows both results, and it then averages them for the main estimate. In general, the two formulas agree closely on short sets, and they drift apart a little as the reps climb. Because of that drift, sets of 10 reps or fewer give the closest estimates.
One Rep Max Calculator Example: 60 kg for 8 Reps
Say you bench press 60 kilograms for 8 clean reps. First, run the Epley formula: 60 × (1 + 8/30) = 60 × 1.2667, which gives 76.0 kg. Next, run the Brzycki formula: 60 × 36/(37 – 8) = 2160/29, which gives 74.5 kg. Then average the two results: (76.0 + 74.5) / 2 = 75.2 kg, so your estimated one rep max is about 75 kg. The table below shows training weights from that 75.2 kg estimate, rounded to one decimal place.
| % of 1RM | Weight | Typical reps |
|---|---|---|
| 95% | 71.5 kg | about 2 reps |
| 90% | 67.7 kg | about 3 to 4 reps |
| 85% | 64.0 kg | about 5 to 6 reps |
| 80% | 60.2 kg | about 7 to 8 reps |
| 75% | 56.4 kg | about 9 to 10 reps |
| 70% | 52.7 kg | about 11 to 12 reps |
| 65% | 48.9 kg | about 13 to 15 reps |
| 60% | 45.1 kg | about 16 to 20 reps |
| 55% | 41.4 kg | about 20 to 25 reps |
| 50% | 37.6 kg | about 25 to 30 reps |
In practice, round these weights to the nearest plate you can actually load, and treat the rep ranges as a guide rather than a rule.
Safety First: An Estimate Is Not a Test
An estimated max is a planning tool, not a challenge. Above all, never test a true one rep max without training experience, warmed-up joints and a spotter you trust. Also, stop any set when your form breaks down, because a strained muscle costs far more training time than one missed rep. Beginners gain strength quickly on moderate weights, so they rarely need percentages above 85 percent at all. If a weight ever feels wrong, rack it and reduce the load, since no formula knows your body better than you do.
Frequently Asked Questions
How accurate is the estimate?
Both formulas usually land within a few percent of a tested max for sets of about 3 to 8 reps taken close to failure. However, accuracy drops on long sets, because endurance varies a lot between lifters. Overall, enter a heavy set from this week rather than an old personal best, and you will get the closest figure.
Which formula should I trust, Epley or Brzycki?
Trust the average, because each formula leans a slightly different way. Epley tends to read a touch higher, and Brzycki a touch lower at moderate reps. The one rep max calculator shows both, so you can see the full range for yourself.
What if I only did 1 rep?
Then the weight you lifted is your one rep max for that day, and the tool simply returns that same weight. Still, remember that tiredness and poor sleep can move that number up or down from week to week.
How often should I retest or re-estimate?
Every 6 to 12 weeks is plenty for most lifters. Meanwhile, let your working sets tell the story between tests: when a weight that once felt heavy starts to feel smooth, your max has probably moved.
Can I use this for any exercise?
Yes, the formulas work for squats, presses, deadlifts, rows and machine lifts alike. However, big compound lifts give the most useful numbers, because you will actually train them by percentage. Small isolation lifts vary more from day to day, so treat their estimates loosely.
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Sources
The two formulas on this page come from Boyd Epley (1985) and Matt Brzycki, whose strength testing method appeared in the Journal of Physical Education, Recreation and Dance in 1993. The percentage and repetition ranges follow the training load chart of the National Strength and Conditioning Association (NSCA), the standard reference coaches use for percentage-based training.