One-Rep Max Calculator
Estimate your one-rep max from a set of reps with the Epley, Brzycki, Lombardi and four other formulas, and get training loads from 50 % to 100 % of 1RM.
Estimate based on published formulas, not medical advice. Talk to a health professional about your situation.
A full set to near failure with good form, ideally 2 to 10 reps.
- Estimated one-rep max
- – kg
- Range across formulas
- –
| Formula | Equation | Estimated 1RM |
|---|
| % of 1RM | Load | ≈ Reps |
|---|
Estimates only. Warm up, use safety bars or a spotter, and stop if you feel pain. Beginners and people with heart, blood pressure or joint problems should get medical and coaching advice before lifting near-maximal loads.
How to use the one-rep max calculator
- Enter the Weight lifted and choose the Unit (kg or lb).
- Enter the Repetitions completed: a full set taken close to failure with good form. Between 2 and 10 reps gives the most reliable estimate.
- Read your Estimated one-rep max, which is the average of seven published formulas, and the Range across formulas.
- The Estimates by formula table shows each equation and its result.
- Choose the Formula for the percentage table (the average by default) and read the loads from 100 % down to 50 % of your 1RM, with the approximate number of reps you could do at each load.
All calculations run in your browser. Clear empties the fields.
What is a one-rep max?
Your one-rep max (1RM) is the heaviest load you can lift once with correct technique in a given exercise. Coaches use it to set training loads as a percentage, for example 3 sets of 5 at 80 %. Testing a true 1RM is tiring and carries some risk, so it is often estimated from a heavier set of several reps instead.
The formulas
With w = weight lifted and r = reps:
| Formula | Equation |
|---|---|
| Epley (1985) | w × (1 + r ÷ 30) |
| Brzycki (1993) | w × 36 ÷ (37 − r) |
| Lombardi (1989) | w × r^0.10 |
| Lander (1985) | 100 × w ÷ (101.3 − 2.67123 × r) |
| Mayhew et al. (1992) | 100 × w ÷ (52.2 + 41.9 × e^(−0.055 × r)) |
| O’Conner et al. (1989) | w × (1 + 0.025 × r) |
| Wathan (1994) | 100 × w ÷ (48.8 + 53.8 × e^(−0.075 × r)) |
Example: 100 kg for 5 reps gives 112.5 kg with Brzycki and O’Conner, 116.7 kg with Epley and 119.0 kg with Mayhew; the average is about 115.5 kg. With a single rep, the tool simply returns the weight lifted.
The approximate reps in the percentage table come from inverting Brzycki (r ≈ 37 − 36 × fraction of 1RM). They are shown only down to 75 %, about 10 reps, because the link between load and reps varies too much below that.
Accuracy
Studies comparing these equations with tested maximums (for example LeSuer et al., Journal of Strength and Conditioning Research, 1997) find them fairly close when the set has 10 reps or fewer, and increasingly off beyond that. Accuracy also depends on the lift: estimates are usually better for the bench press than for the squat or deadlift. Trained lifters, beginners, men and women, and fast- or slow-twitch profiles all differ, so two people with the same 5-rep set can have different real maximums. That is why the tool shows the whole range, not just one number.
Safety
Use the estimate to plan training, not as a reason to attempt a maximal lift. Warm up, use safety bars or a spotter, keep a rep or two in reserve on most sets and stop if you feel pain. Heavy lifting briefly raises blood pressure a lot: if you have a heart condition, high blood pressure, a hernia or a joint injury, or if you are new to strength training, get advice from a doctor and a qualified coach first.
Frequently asked questions
Which 1RM formula is the most accurate?
None is best for everyone. Epley and Brzycki are the most widely used and are very close up to 10 reps; the average of several formulas smooths out their individual biases.
How many reps should I use?
Between 2 and 10, ideally 3 to 6. Sets of more than 10 reps rely on muscular endurance, and the formulas start to disagree.
Why does my estimate differ from my real max?
Technique, fatigue, the exercise itself and your training history all change the relationship between reps and maximum. The formulas describe an average lifter.
Can I use it for machines or bodyweight exercises?
It works for any load you can count reps with, but most equations were built from free-weight lifts like the bench press and squat.
Should I test my real 1RM?
Only if you are experienced, healthy and supervised. For most people, working from an estimated 1RM is safer and good enough.
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