Understanding your 1RM result
The table below shows the widely published relationship between percentage of 1RM and the number of repetitions most lifters can perform at that load (NSCA, Essentials of Strength Training and Conditioning). It is a population average — individual repetition ability at a given percentage varies.
| % of 1RM | Approximate repetitions possible |
|---|---|
| 100% | 1 |
| 95% | 2 |
| 90% | 4 |
| 85% | 6 |
| 80% | 8 |
| 75% | 10 |
| 70% | 12 |
| 65% | 15 |
- Prediction equations are most accurate for sets of 10 repetitions or fewer; above 10 repetitions the estimates become increasingly unreliable.
- Accuracy differs by exercise: equations validated on the bench press do not transfer perfectly to squats, deadlifts or isolation movements.
- An estimated 1RM is not a demonstrated 1RM. Actual maximal attempts involve technique and preparation demands that a formula cannot capture, and heavier singles should only be attempted with appropriate experience, warm-up and supervision.
- Training status matters: LeSuer et al. (1997) found equations tend to underestimate 1RM in the deadlift and squat more than in the bench press.
What is a one-rep max (1RM)?
A one-repetition maximum (1RM) is the maximum weight that can be lifted for a single repetition with proper form in a specific exercise. It is the standard reference for expressing resistance-training loads: strength and conditioning programs typically prescribe intensity as a percentage of 1RM, a convention documented in the NSCA's Essentials of Strength Training and Conditioning.
Testing a true 1RM requires lifting maximal loads, which demands experienced technique, adequate warm-up and appropriate supervision. Prediction equations offer an alternative: they estimate 1RM from a set taken to (or near) repetition failure at a submaximal weight. Research comparing prediction equations to measured maxes — for example LeSuer and colleagues (1997) in the bench press, squat and deadlift — found that the common equations estimate 1RM reasonably well when the test set is 10 repetitions or fewer.
All 1RM equations lose accuracy as repetitions increase, because the relationship between repetitions and load varies between individuals and exercises. Estimates from sets of more than 10 repetitions should be treated as rough approximations, and estimates from low-repetition sets (2–5 reps) are generally the most reliable.
How to use this 1RM calculator
- Enter the weight you lifted in a recent set, using the Metric/Imperial toggle if needed.
- Enter the number of repetitions you completed with good form (1–15; estimates are most reliable at 10 or fewer).
- Read the estimated 1RM from the Epley equation, alongside the Brzycki, Lombardi and Mayhew estimates for comparison.
- Use the 90%, 80% and 70% figures to see how common training-load percentages of the estimate translate into actual weight.
The formulas behind 1RM estimation
The Epley formula (1985) adds one thirtieth of the load per repetition performed. The Brzycki formula (1993) uses a linear relationship between repetitions and percentage of maximum. Lombardi applies a power function of the repetition count, and Mayhew and colleagues fitted an exponential curve to bench-press data. The four equations agree closely at low repetitions and diverge as repetitions increase.
Worked example: 80 kg lifted for 5 repetitions gives an Epley estimate of 80 × (1 + 5/30) ≈ 93.3 kg and a Brzycki estimate of 80 ÷ (1.0278 − 0.0278 × 5) ≈ 90.0 kg. When 1 repetition is entered, the entered weight is itself the demonstrated maximum, so the Epley and Brzycki results equal the input.
The percentage outputs multiply the Epley estimate by 0.9, 0.8 and 0.7. In the repetition-maximum convention published in the NSCA literature, these loads correspond to approximately 4, 8 and 12 repetitions respectively for most lifters, though the true reps-to-load relationship varies by individual and exercise.
Common mistakes
- Estimating 1RM from a high-repetition set (more than 10 reps), where all formulas lose accuracy.
- Using a set that was not close to repetition failure — the equations assume the set was near-maximal effort.
- Treating the estimate as a demonstrated max and attempting it without progressive warm-up singles or a spotter.
- Applying an estimate from one exercise to another — the reps-to-load relationship differs between lifts.
- Comparing estimates from different formulas as if they were independent measurements; they are different curves fitted to the same kind of data.
Часто задаваемые вопросы
How accurate are 1RM calculators?
Validation research such as LeSuer et al. (1997) found that common prediction equations estimate one-rep max reasonably well from sets of 10 repetitions or fewer, typically within a few percent for trained lifters in the bench press. Accuracy decreases as repetitions increase and varies by exercise and training experience, so the result is an estimate, not a guarantee of what can actually be lifted.
Which 1RM formula is best?
No single formula is best in every situation. Epley (1985) and Brzycki (1993) are the most widely used and agree closely at low repetitions — they are mathematically identical at 10 reps and diverge slightly elsewhere. Lombardi and Mayhew provide alternative curve fits. Comparing all four, as this calculator does, shows the realistic range of the estimate.
How many reps should I use for the most reliable estimate?
Sets of 2 to 5 repetitions taken close to repetition failure give the most reliable estimates, because the prediction curves are steepest and best validated in that range. Estimates from sets above 10 repetitions are considerably less accurate, which is why many coaches cap estimation sets at 10 reps.
What is 80% of 1RM used for?
In the repetition-maximum table published by the NSCA, 80% of 1RM corresponds to a load most lifters can move for about 8 repetitions. Percentages in the 70–85% range are commonly associated with general strength and hypertrophy work in published training literature, while loads at or above 85% are associated with maximal-strength training. Individual programming is best guided by a qualified coach.
Is it safe to test a true 1RM?
Maximal testing places high demands on technique and tissue tolerance. Sports-medicine and strength organizations advise that true 1RM tests be performed only after adequate technical practice, with a thorough warm-up, appropriate equipment and supervision such as a spotter. Estimating 1RM from submaximal sets, as this calculator does, avoids those demands entirely.
Why do the four formulas give different numbers?
Each formula is a different mathematical curve fitted to observed reps-to-load data: Epley is linear in repetitions, Brzycki is linear in percentage terms, Lombardi is a power function and Mayhew is exponential. They converge at very low repetitions and spread apart as repetitions rise, which reflects genuine uncertainty in predicting a maximum from a submaximal set.
Источники
- Epley B. Poundage chart. Boyd Epley Workout. Lincoln, NE: Body Enterprises, 1985.
- Brzycki M. Strength testing — predicting a one-rep max from reps-to-fatigue. Journal of Physical Education, Recreation & Dance 1993; 64(1): 88–90.
- Mayhew JL, Ball TE, Arnold MD, Bowen JC. Relative muscular endurance performance as a predictor of bench press strength in college men and women. Journal of Applied Sport Science Research 1992; 6(4): 200–206.
- 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. Journal of Strength and Conditioning Research 1997; 11(4): 211–213.
- Haff GG, Triplett NT (eds). Essentials of Strength Training and Conditioning, 4th edition. NSCA / Human Kinetics, 2016 — %1RM repetition-maximum relationships.
- American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription, 11th edition. Wolters Kluwer, 2021.