Epley
1RM = w × (1 + r / 30)
Published by Boyd Epley in 1985 and still one of the most used formulas. Below 10 reps it gives a little more than Brzycki. At 10 reps the two give the same result.
What is a 1RM?
Your 1RM, or one rep max, is the heaviest weight you can lift once with good form. Coaches use it to measure strength and to set training loads. A plan might say 5 sets of 5 reps at 80% of 1RM, and the 1RM tells you what weight that is.
A true max test is hard on the body and needs a long warm-up. A 1RM calculator gives you a close estimate from a normal training set, so you can plan loads without a max test.
How to use the 1RM calculator
- 1 Pick the lift. It only changes the labels, not the math.
- 2 Enter the weight you lifted and choose kg or lb.
- 3 Enter how many reps you did, from 1 to 12. Use a set that you took close to failure.
- 4 Read your estimated 1RM and the load table. Copy the link to save or share the result.
Use a recent set with good form. A set of 3 to 6 hard reps usually gives a closer estimate than a set of 10 or more.
The three 1RM formulas
The calculator uses three well-known formulas. In each one, w is the weight you lifted and r is the number of reps.
Brzycki
1RM = w × 36 / (37 − r)
Published by Matt Brzycki in 1993 in the Journal of Physical Education, Recreation and Dance. It is usually recommended for sets of up to 10 reps. Above that, the result rises fast.
Lombardi
1RM = w × r0.10
Named after V. P. Lombardi. It gives the highest estimate of the three at 2 to 5 reps and the lowest at 8 reps or more, so it pulls the average down for long sets.
Example: 80 kg for 8 reps
- Epley
- 101.3 kg
- Brzycki
- 99.3 kg
- Lombardi
- 98.5 kg
- Average
- 99.7 kg
Why the main number is an average
No single formula fits every lifter. The calculator shows the average of the three as your estimated 1RM, and each result below it, so you can see how far apart they are. Above 8 reps, the results move further apart with each extra rep, and the estimate gets less certain.
How accurate are 1RM formulas?
A formula gives an estimate, not a test result. LeSuer and colleagues (1997, Journal of Strength and Conditioning Research) compared seven formulas, including Epley, Brzycki and Lombardi, in the bench press, squat and deadlift. The estimates were closest for the bench press. For the deadlift, the formulas tended to give values below the real 1RM.
All formulas lose accuracy as the reps go up. That is why this calculator accepts up to 12 reps and shows a note above 10.
How trainers use 1RM percentages
Most strength programs give loads as a percentage of 1RM. The same plan then fits a beginner and an advanced lifter, because each person's loads come from their own max. When the 1RM goes up, the loads go up with it.
The table shows common rep ranges for each percentage. Use them as a starting point. The number of reps a person can do at a given percentage is different for each lift and each person, and it is harder to predict at lower percentages.
| % of 1RM | Typical reps | Typical use |
|---|---|---|
| 100% | 1 | Maximum strength |
| 95% | 2 | Maximum strength |
| 90% | 3–4 | Maximum strength |
| 85% | 5–6 | Strength |
| 80% | 7–8 | Strength |
| 75% | 9–10 | Muscle growth |
| 70% | 11–12 | Muscle growth |
| 65% | 13–15 | Muscle growth |
| 60% | 16–20 | Warm-ups and technique |
| 55% | 21–24 | Warm-ups and technique |
| 50% | 25+ | Warm-ups and technique |
The typical use column is a guide, not a rule. Muscles also grow with lighter loads when the sets are hard.
Many coaches also adjust loads by how the sets feel, with RPE (rate of perceived exertion) or reps in reserve. On a bad day the load comes down, on a good day it can go up. Update the 1RM every 4 to 8 weeks, or at the end of a training block, so the percentages stay correct.
How to test a true 1RM safely
A real max test gives the most exact number, but it needs good technique, a careful warm-up and safety equipment. A common way to do it:
- 1 Warm up for 5 to 10 minutes with light cardio and mobility work for the lift.
- 2 Do a light set of 5 to 10 reps at about 50% of your expected max. Rest 1 to 2 minutes.
- 3 Do 3 to 5 reps at about 70%, then 1 to 2 reps at about 80 to 85%. Rest 2 to 3 minutes.
- 4 Do a single rep at about 90%. Rest 3 to 5 minutes.
- 5 Try your max. If it moves well, add a small amount and try again. Stop after 3 to 5 heavy attempts, or when your form gets worse.
Use a spotter on the bench press and safety bars in the squat rack. Count only the heaviest lift that you finished with a full range of motion and good form.
When not to test a true 1RM
- You are new to the lift, or your technique is not stable yet.
- You have pain or an injury, or you are coming back from one.
- You are tired, short on sleep or in a hard diet phase.
- You have no spotter or safety bars.
- You have a health condition and no approval from a doctor.
In these cases, use this calculator with a set of 3 to 6 reps. For most training plans, a good estimate is enough.
Frequently asked questions
What does 1RM mean?
1RM stands for one rep max, or one-repetition maximum. It is the heaviest weight you can lift once with good form in a given exercise.
How accurate is a 1RM calculator?
For a hard set of up to 10 reps, the estimate is usually close to your real max, but it can be off by a few kilograms. It depends on the lift, your training experience and how close to failure you took the set. Use it to plan training, not as a competition result.
Which 1RM formula is the most accurate?
No formula is the best for everyone. Studies that compared formulas found that the accuracy depends on the lift and on the number of reps. That is why this calculator shows the average of Epley, Brzycki and Lombardi, and each result on its own.
How many reps should I enter for the best estimate?
Use a hard set of about 3 to 6 reps with good form. The formulas get less accurate as the reps go up, especially above 10. A set that you stopped long before failure gives a 1RM that is too low.
Does the calculator work for bench press, squat and deadlift?
Yes. The formulas are the same for every lift, and the lift you pick only changes the labels. In research, the estimates were closest for the bench press, and for the deadlift the formulas tended to give values below the real 1RM.
Can I use RPE or reps in reserve with this calculator?
The formulas expect a set close to failure. If you stopped with reps left, add them to the reps you did for a rough estimate. For example, 5 reps at RPE 8 (2 reps left) count as about 7 reps.
How often should I check my 1RM again?
Many coaches update it every 4 to 8 weeks, or at the end of a training block. Enter a recent hard set to update the estimate without a max test.
Should beginners test their 1RM?
Usually not. Beginners get stronger quickly and are still learning the technique, so a max test adds risk for little benefit. An estimate from a set of 5 to 8 reps is enough to plan the loads.
Disclaimer
This calculator gives estimates for training only. It is not medical advice. If you have an injury, pain or a health condition, talk to a doctor before hard training, and use safety equipment for heavy lifts.
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