Your one-rep max (1RM) is the heaviest weight you can lift once with good technique for a given exercise. You do not have to lift that weight to find it out. Formulas such as Epley and Brzycki estimate it from a lighter set done to near failure, and the estimate works best for sets of about 2 to 10 reps.
What is a one-rep max?
A 1RM is a measure of maximal strength on one exercise, such as a squat, bench press or deadlift. Coaches and lifters use it to set training weights as a percentage of that number, so that sessions stay at a sensible difficulty as strength changes.
Testing a true 1RM carries more risk than lighter work, and is tiring for the nervous system. Estimating it from a set of several reps is safer and good enough for most programmes.
The five common formulas
With weight w and reps r, the common formulas are:
- Epley: w × (1 + r ÷ 30)
- Brzycki: w × 36 ÷ (37 − r)
- Lander: 100 × w ÷ (101.3 − 2.67123 × r)
- Lombardi: w × r^0.10
- O’Conner: w × (1 + 0.025 × r)
They all give the same answer at one rep (the weight itself) and agree closely at low reps. They spread out as reps rise, which is why averaging them, as the One-rep max calculator calculator does, gives a more balanced figure. Brzycki breaks down at high reps, so estimates beyond about 12 reps are not reliable.
A worked example
Say you lift 100 kg for 5 reps. The calculator gives:
| Formula | Estimated 1RM |
|---|---|
| Epley | 116.7 kg |
| Brzycki | 112.5 kg |
| Lander | 113.7 kg |
| Lombardi | 117.5 kg |
| O’Conner | 112.5 kg |
| Average | 114.6 kg |
The spread is about 5 kg, which shows that any single number is an estimate. Take the average as your working figure and adjust it from experience.
Using percentages of your 1RM
Once you have a 1RM, training weights are set as a percentage. From the same 114.6 kg estimate:
| Percentage | Weight | Rough reps possible |
|---|---|---|
| 95% | 109 kg | about 2 |
| 90% | 103 kg | about 4 |
| 85% | 97.5 kg | about 6 |
| 80% | 91.5 kg | about 8 |
| 75% | 86 kg | about 10 |
| 70% | 80 kg | about 12 |
| 60% | 68.5 kg | about 20 |
The reps are typical averages, not promises. Some people manage more at a given percentage, especially on large leg exercises, and fewer on small isolation exercises. Heavy work around 80 to 90% builds maximal strength, while moderate weights around 65 to 75% are often used for more reps.
Getting a better estimate
- Use a set taken close to failure, where you could not do another rep with good form.
- Keep the technique the same as in your usual training, with full range of motion.
- Prefer sets of 3 to 8 reps. Sets of 12 or more drift further from your true max.
- Re-test every few weeks, because your 1RM changes as you get stronger.
- Estimates apply to one exercise at a time. Your squat 1RM tells you nothing about your bench press.
If you are also thinking about how hard you are working in cardio, see Heart rate zones explained: how to find your maximum and train by zone, and for the food side of strength training, Macros for beginners: protein, carbs and fat covers protein, carbohydrate and fat.
Note: This is general information, not medical advice. If you are new to lifting, returning after injury or have a health condition, get advice from a qualified coach or healthcare professional. Never attempt a true max without warming up, good technique and a spotter or safety bars.
Try the calculator
Enter the weight and reps from your last hard set in the One-rep max calculator calculator. You will get five estimates, their average, and a table of weights from 95% down to 50% of your 1RM.
Open the free One-rep max calculator
How to work out a 1RM by hand
You do not need a calculator to check an estimate. Two of the formulas are quick enough to do on a phone or in your head.
Epley: multiply the reps by 1/30 (divide by 30), add 1, then multiply by the weight. For 140 kg for 3 reps: 3 ÷ 30 = 0.1, so 1.1 × 140 = 154 kg.
Brzycki: subtract the reps from 37, divide 36 by that number, then multiply by the weight. For the same set: 37 − 3 = 34, 36 ÷ 34 = 1.0588, and 1.0588 × 140 = 148.2 kg.
Epley gives 154 kg and Brzycki gives 148.2 kg, a gap of nearly 6 kg from one set. That is normal, and it is the reason to look at a range rather than a single figure. A sensible rule is to plan with the lower to middle part of the range and let your next heavy session show whether the number was too high or too low.
Worked example 2: a heavy set of three
Suppose you squat 140 kg for 3 hard reps. The one-rep max calculator gives these estimates:
| Formula | Estimated 1RM |
|---|---|
| Epley | 154 kg |
| Brzycki | 148.2 kg |
| Lander | 150.1 kg |
| Lombardi | 156.3 kg |
| O’Conner | 150.5 kg |
| Average | 151.8 kg |
From the 151.8 kg average, the working weights come out as:
| Percentage of 1RM | Weight | Typical use |
|---|---|---|
| 90% | 136.5 kg | Heavy singles, doubles or triples |
| 85% | 129 kg | Sets of about 5 to 6 |
| 80% | 121.5 kg | Sets of about 6 to 8 |
| 75% | 114 kg | Moderate sets of 8 to 10 |
| 70% | 106.5 kg | Higher-rep work, up to about 12 |
Notice how little the rep count changed the picture. A set of 3 is a more reliable basis than a set of 12, because the formulas were built around lower-rep sets and have less to extrapolate.
Pounds, kilograms and loading the bar
The formulas work in any unit, so you can enter pounds directly. A 225 lb set of 5 gives an average of 257.8 lb, with Epley at 262.5 lb and Brzycki at 253.1 lb.
The result will rarely match the plates you own. Round to the nearest load you can actually put on the bar, and round down if you are unsure. Many gyms have small plates that add 1 kg or 2.5 lb per side, which makes it easy to land close to the target. Remember that the bar itself counts towards the weight, so a target of 121.5 kg means the bar plus plates adds up to that figure, not plates alone.
Using your 1RM to plan a training week
A percentage table is a starting point, not a prescription. Here is one simple way people use it:
- Heavy day: 85 to 90% for a few sets of 2 to 4 reps, with long rests of three minutes or more.
- Moderate day: 75 to 80% for sets of 5 to 8 reps.
- Lighter day: 65 to 70% for technique and volume, stopping well short of failure.
Progress is usually slow and uneven. Adding a small amount to the bar when all planned reps feel solid, and re-testing your estimate every few weeks, keeps the numbers honest. If a weight that should be 80% feels like 95%, your 1RM estimate is too high, or you are tired, under-fuelled or short of sleep. Food and recovery matter here, and Macros for beginners: protein, carbs and fat and Calories and TDEE: how many calories do you need? cover the nutrition side.
Common mistakes when estimating a 1RM
- Using a set that was not close to failure. If you stopped with five reps left in reserve, the formulas will underestimate your max.
- Counting sloppy reps. Bouncing the bar off the chest, shallow squats or a heaving back all inflate the figure. Only count reps you would accept in a competition-style lift.
- Mixing exercises. A leg press result says little about a back squat. Estimate each lift separately.
- Trusting a high-rep set. Twenty reps of a light weight tests muscular endurance, and the formulas lose accuracy well before that.
- Treating the number as fixed. Fatigue, a poor night’s sleep or a different bar can move a day’s performance by several per cent.
- Skipping the warm-up. Estimating from a cold set can both mislead you and raise the chance of injury.
Glossary
- 1RM: the most weight you can lift for one rep with good form.
- RPE: rate of perceived exertion, a 1 to 10 scale where 10 means nothing left in the tank.
- Reps in reserve (RIR): how many more reps you could have done with good form.
- Failure: the point where you cannot complete another rep without breaking form.
- Spotter: someone positioned to help if a lift goes wrong; safety bars do a similar job on a squat or bench.
Frequently asked questions
Which 1RM formula is best?
None is best for everyone. Epley and Brzycki are the most widely used, and an average of several formulas reduces the chance that one of them is badly off.
How accurate is an estimated 1RM?
Within a few per cent for most people on a well-practised lift when the set is hard, but less so for high reps or unfamiliar exercises. Treat it as a guide and adjust.
How many reps should I use to estimate it?
Between 2 and 10 reps near failure is a good range. At 1 rep the weight is your max, and above about 12 reps the formulas are less reliable.
Do I need to test my true max?
No. Most training programmes can be run from an estimate. If you do want to test, be experienced, warm up thoroughly and use a spotter or safety bars.
Can I use the 1RM formulas for bodyweight exercises like pull-ups?
Yes, if you add your body weight and any extra load together before entering the weight. For a 80 kg person doing weighted pull-ups with 20 kg added, enter 100 kg. The result is only a rough guide, because body weight is not perfectly shared across the movement.
How often should I recalculate my 1RM?
Every three to six weeks suits most people, or after a block of training where a lift has clearly moved. Beginners often improve quickly and may want to update more often.
Why does my estimated 1RM change from day to day?
Sleep, food, stress, warm-up and how fresh you are all affect performance. A single hard set is a snapshot, so look at the trend over several sessions rather than one result.
Is an estimated 1RM safe to lift?
The estimate is a prediction, not a promise, and lifting right at your maximum carries more risk than lighter work. Only test a true max if you are experienced, well warmed up and have a spotter or safety bars.