One-rep max calculator
Your one-rep max, estimated four ways.
- Epley (1985)
- 116.7 kg
- Brzycki (1993)
- 112.5 kg
- Lombardi (1989)
- 117.5 kg
- Mayhew et al. (1992)
- 119.0 kg
- Average in pounds
- 256.6 lb
| % of 1RM | Load | Reps, about |
|---|---|---|
| 100% | 116.5 kg | 1 |
| 95% | 110.5 kg | 2–3 |
| 90% | 105.0 kg | 3–5 |
| 85% | 99.0 kg | 5–6 |
| 80% | 93.0 kg | 8 |
| 75% | 87.5 kg | 10 |
| 70% | 81.5 kg | 12–13 |
| 65% | 75.5 kg | 14–16 |
| 60% | 70.0 kg | 15–20 |
| 55% | 64.0 kg | 17–25 |
| 50% | 58.0 kg | 19–30 |
Loads are your average estimate, rounded to the nearest 0.5 kg. Reps are approximate, from the Epley and Brzycki equations solved for reps; real numbers vary by exercise and person.
For adults who already lift with good technique. An estimate from one set, not a tested maximum or medical advice. If you have a medical condition or an injury, or are pregnant, ask your doctor before lifting near your maximum.
This one-rep max calculator estimates the heaviest weight you could lift once from a set you have already done: the weight and the reps you managed. It runs four published equations, Epley, Brzycki, Lombardi and Mayhew, shows their average and turns it into a percentage table for planning your training.
- Free, no sign-up
- Kilograms or pounds
- Runs in your browser; nothing is saved
How the calculator works →Coaching clients? Try Trainaq free →
What is a one-rep max?
Your one-rep max, or 1RM, is the heaviest weight you can lift once with good form in a given exercise. Testing it means lifting at your limit, so a one-rep max calculator estimates it from a lighter set taken close to failure instead. Estimates are most reliable from sets of 10 reps or fewer.
- Four equations: Epley (1985), Brzycki (1993), Lombardi (1989) and Mayhew et al. (1992)
- Each result shown, with their average as the headline figure
- A percentage table from 100% down to 50%, with about how many reps each load allows
- Kilograms or pounds, with a warning above 10 reps
How it works
How does this one-rep max calculator work?
You enter the weight and reps of one hard set. The calculator runs the set through four published equations, each relating reps to a percentage of your maximum, and averages the four answers. It then works out the loads for 100% down to 50% of that estimate, with about how many reps each allows.
Do one hard set
Pick a weight you can lift for 10 reps or fewer and do as many reps as you can with good form, stopping when the next rep would fail or your technique would slip. A set from your last session works if you took it close to failure.
- In one study, a 5-rep max predicted the 1RM better than a 10- or 20-rep max
- Count only reps with your full range of motion
Enter the weight and reps
Type the weight in kilograms or pounds and the reps you completed. The equations scale with the weight, so the unit makes no difference to the maths. One rep is taken as your 1RM itself. Above 10 reps the calculator still answers, up to 15, with a warning.
- Switching units converts the weight you typed
- Whole reps only: a rep you could not finish does not count
Four equations, one average
Epley, Brzycki, Lombardi and Mayhew each describe how the weight you can lift falls as reps rise. Up to 10 reps their answers stay within 9 kg of each other for every 100 kg lifted. The calculator shows all four and uses their average as the headline figure.
- At 15 reps the gap grows to more than 30 kg per 100 kg lifted
- The spread is a fair reminder that this is an estimate
Plan from the percentage table
The table lists the load at each 5% step from 100% down to 50% of your estimated 1RM, rounded to 0.5 kg or 1 lb, with about how many reps the Epley and Brzycki equations allow there. Use it to choose starting weights, then adjust from how the sets go.
- Measured reps at each load vary by exercise and person: see the table below
Formulas
Which formulas does the calculator use?
Four equations that a 1997 study tested on the bench press, squat and deadlift: Epley, Brzycki, Lombardi and Mayhew et al. Each takes the weight lifted and the reps completed. Epley is a straight line, Brzycki curves upwards, Lombardi is a gentle power curve and Mayhew is exponential. The headline figure is their average.
1RM = w × (1 + r ÷ 30)1RM = 100 × w ÷ (102.78 − 2.78 × r)1RM = w × r^0.101RM = 100 × w ÷ (52.2 + 41.9 × e^(−0.055 × r))1RM = (Epley + Brzycki + Lombardi + Mayhew) ÷ 4Load = 1RM × p ÷ 100- w: weight lifted, in kg or lb; the answer comes out in the same unit
- r: reps completed, 1 to 15; with one rep, 1RM = w
- e: the number 2.718…; r^0.10 is r to the power of 0.10
- p: a percentage of the 1RM
- Epley’s 1 ÷ 30 is often printed as 0.0333, and Brzycki is also written w ÷ (1.0278 − 0.0278 × r)
Percentage table
How many reps can you do at each percentage of your 1RM?
Roughly 8 reps at 80%, 10 at 75% and 12 to 13 at 70%, going by the Epley and Brzycki equations. Measured averages from a 2024 review of 269 studies run about 2 reps higher at those loads, and people vary. The exercise matters too: lifters manage fewer reps on the bench press than the leg press.
| % of 1RM | Equations (Epley–Brzycki) | Measured, all exercises | Measured, bench press |
|---|---|---|---|
| 100% | 1 | 1 | 1 |
| 95% | 2–3 | 3 | 3 |
| 90% | 3–5 | 5 | 4 |
| 85% | 5–6 | 7 | 6 |
| 80% | 8 | 10 | 9 |
| 75% | 10 | 12 | 12 |
| 70% | 12–13 | 15 | 14 |
| 65% | 14–16 | 17 | 17 |
| 60% | 15–20 | 20 | 19 |
| 55% | 17–25 | 22 | 23 |
| 50% | 19–30 | 26 | 27 |
Equations: Epley and Brzycki solved for reps, rounded. Measured: average reps to failure from the meta-regression by Nuzzo et al. (2024), its main model and bench press model, rounded; 100% is one rep by definition. People vary: one standard deviation is about 2 reps at 90% and 6 reps at 50%.
Worked example
What does a worked example look like?
Say you squat 100 kg for 5 reps. Epley gives 100 × (1 + 5 ÷ 30) = 116.7 kg, Brzycki 10,000 ÷ 88.88 = 112.5 kg, Lombardi 100 × 5^0.10 = 117.5 kg and Mayhew 119.0 kg. Their average, the headline figure, is 116.4 kg, so 80% of your estimated 1RM is about 93 kg.
- Mayhew: 52.2 + 41.9 × e^(−0.275) = 84.0%, so the 1RM is 100 ÷ 0.840 = 119.0 kg
- The average: (116.7 + 112.5 + 117.5 + 119.0) ÷ 4 = 116.4 kg
- 80% of 116.4 kg is 93.1 kg, which the table rounds to 93.0 kg; the equations allow about 8 reps there
- At 75%, 87.5 kg, they allow about 10 reps
Equations compared
How do the four equations compare?
They were published separately and bend differently as reps rise. From 2 to 7 reps Mayhew gives the highest answer and Brzycki the lowest. Epley and Brzycki almost meet at 10 reps, where Lombardi gives the lowest. Beyond 10 reps they spread far apart, which is why the calculator warns you there.
| Equation | Where it was published | At 5 reps | At 10 reps |
|---|---|---|---|
| Epley (1985) | A poundage chart in the Boyd Epley Workout | × 1.167 | × 1.333 |
| Brzycki (1993) | Journal of Physical Education, Recreation and Dance | × 1.125 | × 1.334 |
| Lombardi (1989) | The textbook Beginning Weight Training | × 1.175 | × 1.259 |
| Mayhew et al. (1992) | A study of the bench press in 435 college students | × 1.190 | × 1.309 |
Each multiplier is the estimate divided by the weight lifted. LeSuer et al. (1997) tested all four, with three other equations, against tested maxes on the bench press, squat and deadlift.
Accuracy
How accurate is an estimated one-rep max?
Reasonably, on the lifts and people studied. In Mayhew’s original bench press data the standard error was 4.8 kg. A 1997 test of seven equations found close correlations with tested maxes but statistically significant average errors on the bench press and squat for most of them, and all seven underestimated the deadlift.
- Mayhew et al. (1992): 184 men and 251 women at 55 to 95% of their 1RM; a standard error of 5.4 kg in a second group
- LeSuer et al. (1997): 67 untrained students; correlations above 0.95 for every equation
- Reynolds et al. (2006): use no more than 10 reps in linear equations; a 5-rep max predicted best
- Mayhew et al. (2008): in 103 women, the equations were more accurate with fewer than 10 reps
Exercise and experience
Why do estimates differ by exercise and training experience?
The reps you can do at a given percentage change with the exercise and with how you train. A 2024 meta-regression found more reps on the leg press than the bench press at every load, and endurance runners have managed far more reps than weightlifters at the same moderate load. One equation cannot fit everyone.
- At 80% of 1RM: about 9 reps on the bench press and 13 on the leg press (Nuzzo et al. 2024)
- Leg press at 70%: endurance runners 39.9 reps, weightlifters 17.9 (Richens and Cleather 2014)
- After 12 weeks of training, women in one study changed their reps at the same relative load by very different amounts (Mayhew et al. 2008)
- Sex, age and training status made little clear difference in the 2024 review
- Re-estimate with the same exercise, done the same way, so the numbers compare
Testing safely
How do I test a true one-rep max safely?
Only test a true maximum in a lift you have practised, after a thorough warm-up, with a spotter or safety bars set at the right height. Work up in a few heavier singles with full rest between them, and stop when your technique starts to slip. Tested carefully, a 1RM repeats well from one session to the next.
- Warm up with lighter sets of the same lift, cutting the reps as the weight climbs
- Bench press with a spotter; squat in a rack with safety bars set just below the bottom position
- A 2020 review of 32 studies found high test-retest reliability, with a median ICC of 0.97
- With a medical condition, an injury or a pregnancy, ask your doctor first
Using it
How do I use my one-rep max to plan training?
Use it to choose loads. If a program asks for sets at a percentage of your 1RM, read the load from the table. If it asks for a number of reps, start from the matching row and adjust: if the last rep came easily, add weight next time; if you missed reps, take some off.
- Re-estimate from a recent hard set as you get stronger
- Compare like with like: the same exercise, depth and range of motion
- Keep a log, so each estimate comes from real sets
For coaches
How do coaches use one-rep max estimates with clients?
Coaches use them to set starting loads and to track strength without frequent max tests. In Trainaq you put weights and reps on each set of a client’s workout. Clients log their sets in the free Trainaq app, see last time’s numbers as they train, and get an alert the moment they set a personal record.
- PR alerts cover weight, estimated 1RM, reps and duration
- Each client’s progress page charts the best estimated 1RM per day (Epley) for the lifts they train most
- You see every logged set, PR and note from their sessions
Sources
Sources
- LeSuer DA, McCormick JH, Mayhew JL, Wasserstein RL, Arnold MD. The accuracy of prediction equations for estimating 1-RM performance in the bench press, squat, and deadlift. J Strength Cond Res. 1997;11(4):211–213.
- Mayhew JL, Ball TE, Arnold MD, Bowen JC. Relative muscular endurance performance as a predictor of bench press strength in college men and women. J Appl Sport Sci Res (now J Strength Cond Res). 1992;6(4):200–206.
- Brzycki M. Strength testing: predicting a one-rep max from reps-to-fatigue. J Phys Educ Recreat Dance. 1993;64(1):88–90.
- Reynolds JM, Gordon TJ, Robergs RA. Prediction of one repetition maximum strength from multiple repetition maximum testing and anthropometry. J Strength Cond Res. 2006;20(3):584–592.
- Mayhew JL, Johnson BD, Lamonte MJ, Lauber D, Kemmler W. Accuracy of prediction equations for determining one repetition maximum bench press in women before and after resistance training. J Strength Cond Res. 2008;22(5):1570–1577.
- Nuzzo JL, Pinto MD, Nosaka K, Steele J. Maximal number of repetitions at percentages of the one repetition maximum: a meta-regression and moderator analysis of sex, age, training status, and exercise. Sports Med. 2024;54(2):303–321.
- Richens B, Cleather DJ. The relationship between the number of repetitions performed at given intensities is different in endurance and strength trained athletes. Biol Sport. 2014;31(2):157–161.
- Grgic J, Lazinica B, Schoenfeld BJ, Pedisic Z. Test-retest reliability of the one-repetition maximum (1RM) strength assessment: a systematic review. Sports Med Open. 2020;6(1):31.
FAQ
One-rep max calculator FAQ
Is an estimated 1RM as accurate as testing it?
No. A 2020 review of 32 studies found a tested 1RM highly repeatable, varying by about 4% between sessions at the median. An estimate can be off by several kilograms, more so above 10 reps or on lifts the equations were not tested on. It does spare you a maximal lift, and it is close enough for planning.
Which one-rep max formula is the most accurate?
None wins everywhere. Accuracy depends on the exercise and the people tested: in the 1997 comparison, most equations showed significant average errors on the bench press and squat, and all of them underestimated the deadlift. Averaging the four, as this calculator does, avoids leaning on any one equation’s quirks. A tested max beats them all.
Why does the calculator warn above 10 reps?
The equations lose accuracy as reps rise. Studies of the bench press and leg press found sets of 10 or fewer gave the best estimates, and the four equations drift far apart beyond that. The calculator still answers up to 15 reps with a warning, though a heavier set of 10 or fewer gives a better figure.
Why do the four formulas give different answers?
They were published separately, and each assumes a different shape for how the weight you can lift falls as reps rise. Epley is a straight line, Brzycki curves upwards, Lombardi flattens out and Mayhew is exponential. At 5 reps they differ by 6.5 kg per 100 kg lifted, and above 10 reps the gap grows quickly.
Does the calculator work for dumbbells, machines and other lifts?
Treat it as a rough guide there. Mayhew’s equation came from the bench press, and the 1997 comparison used the bench press, squat and deadlift. Reps at a given percentage also differ between exercises: a 2024 review found more on the leg press than the bench press. For other lifts, adjust from your logged sets.
How often should I re-estimate my one-rep max?
Whenever a recent hard set shows you have got stronger, or every few weeks during a training block. Use the same exercise and technique each time so the estimates compare. If you train with a coach on Trainaq, they see the best estimated 1RM of each day charted for the lifts you train most.
