1-Rep Max Calculator
Enter the weight you lifted and how many clean reps you completed. The calculator estimates the heaviest single you could lift and lists the weights that correspond to common rep targets.
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Created by the Reeliy Editorial Team. Last updated: Oct 19, 2026
What is a one-rep max?
Your one-repetition maximum (1RM) is the heaviest weight you can lift for a single repetition of an exercise with proper form. It is a standard measure of maximal strength in the squat, bench press, deadlift, overhead press and similar lifts, and the reference point for percentage-based training programs.
Testing a true max takes warm-up, rest, spotters and some risk. A prediction equation avoids that: you perform a set with a lighter load, and the formula estimates the single you could have managed from the number of reps you completed.
How to use the calculator
Enter the weight you used (from 1 to 4,000, in kg or lb), the number of repetitions you completed, and choose a formula. Epley is selected first. Repetitions must be a whole number from 1 to 30; for the most reliable estimate use a set of 10 reps or fewer, with 6 to 10 working best, and stop the set when your form would break rather than at a fixed number.
The table gives the estimated 1-repetition max to one decimal place, followed by six rep targets: the 3, 5, 7, 10, 15 and 20-rep maximums. Each shows the weight you could lift for that many reps and what percentage of your 1RM it is. The weights are rounded to whole kilograms or pounds.
Because every row comes from the same formula, the table is internally consistent: if your own rep count appears in it (for example 5 or 10), that row gives back the weight you entered, and heavier rows always have fewer reps.
The 1RM formulas
All of the equations have the same shape: 1RM = weight × a factor that depends on the number of reps (r). They differ in how fast the factor grows. The calculator uses these forms:
| Formula | Estimated 1RM |
|---|---|
| Epley | weight × (1 + r ÷ 30) |
| Brzycki | weight × 36 ÷ (37 − r) |
| Lombardi | weight × r^0.10 |
| Mayhew et al. | weight × 100 ÷ (52.2 + 41.9 × e^(−0.055 r)) |
| Wathen | weight × 100 ÷ (48.8 + 53.8 × e^(−0.075 r)) |
| Adams | weight ÷ (1 − 0.02 r) |
| Baechle | weight × (1 + 0.033 r) |
| Berger | weight ÷ (1.0261 × e^(−0.0262 r)) |
| Brown | weight × (0.9849 + 0.0328 r) |
| Kemmler et al. | weight × (0.988 + 0.0104 r + 0.0019 r² + 0.0000584 r³) |
| Landers | weight × 100 ÷ (101.3 − 2.67123 r) |
| Naclerio et al. | weight ÷ (0.951 × e^(−0.021 r)) |
| O'Conner et al. | weight × (1 + 0.025 r) |
To fill the rep-max table, the calculator divides the estimated 1RM by the same factor for 3, 5, 7, 10, 15 and 20 reps, and the percentage is 100 divided by that factor.
Worked example. You squat 100 kg for 8 clean reps. With Epley the factor is 1 + 8 ÷ 30 = 1.2667, so your estimated 1RM is 126.7 kg. The 5-rep maximum is 126.67 ÷ (1 + 5 ÷ 30) = 126.67 ÷ 1.1667 = 108.6, which rounds to 109 kg and equals 86% of the 1RM. The 10-rep maximum is 126.67 ÷ 1.3333 = 95 kg, exactly 75%.
How the estimates compare
Different equations were fitted to different lifters and exercises, so they do not agree exactly. For one set of 100 kg for 8 reps they give:
| Formula | 1RM from 100 kg × 8 reps |
|---|---|
| Wathen | 127.7 kg |
| Epley | 126.7 kg |
| Baechle | 126.4 kg |
| Mayhew et al. | 126.3 kg |
| Landers | 125.1 kg |
| Brown | 124.7 kg |
| Naclerio et al. | 124.4 kg |
| Brzycki | 124.1 kg |
| Lombardi | 123.1 kg |
| Kemmler et al. | 122.3 kg |
| Berger | 120.2 kg |
| O'Conner et al. | 120.0 kg |
| Adams | 119.0 kg |
Under 10 reps the thirteen formulas stay within roughly 10% of one another. The gap widens quickly with higher reps. For 100 kg lifted 20 times, Lombardi predicts a 1RM of about 135 kg, Epley about 167 kg, Brzycki about 212 kg and Kemmler about 242 kg. Epley and Brzycki happen to agree at 10 reps (both 133.3 kg for 100 kg), but Brzycki is more conservative below that and far more aggressive above it.
In practice: keep sets under 10 reps when you want an estimate, use one formula consistently so that changes reflect your strength and not the equation, and treat the number as a planning figure rather than a record.
Testing a real one-rep max
A direct test is the benchmark if you have the experience and a spotter or safety bars. Research reviews show that 1RM testing is highly repeatable when the protocol is standardised. A typical protocol:
- Warm up with light sets of 5 to 10 reps, then a few progressively heavier singles.
- Make the first attempt at a weight you are confident of, about 85 to 90% of your estimated max.
- Rest 3 to 5 minutes between attempts and add weight in small steps.
- Stop after about 3 to 5 attempts at maximal effort; the last successful lift with good form is your 1RM.
Maximal lifts carry a risk of injury. Beginners, people returning from injury or with heart or blood pressure problems should not test a true max without professional guidance. The estimates here are for general fitness planning; see the disclaimer.
Training with your 1RM
Most strength programs prescribe loads as a percentage of 1RM. A widely used guide pairs about 85% and above with strength work (up to roughly 6 reps), 67 to 85% with muscle growth (6 to 12 reps) and about 67% or less with muscular endurance (12 or more reps). Individual response varies a lot, so use these zones as starting points.
| % of 1RM | Load for a 126.7 kg 1RM |
|---|---|
| 60% | 76.0 kg |
| 70% | 88.7 kg |
| 75% | 95.0 kg |
| 80% | 101.3 kg |
| 85% | 107.7 kg |
| 90% | 114.0 kg |
| 95% | 120.3 kg |
Re-test or re-estimate every few weeks, because your 1RM moves as you train. If you are also managing your diet around training, the TDEE calculator estimates daily Calories, and the target heart rate calculator helps with cardio sessions.
Frequently asked questions
How accurate is a 1RM calculator?
Reasonably close for sets of up to about 10 reps, where the formulas differ from each other by less than about 10%, and much less reliable beyond that. Accuracy also depends on exercise, training experience and how strictly you counted reps, so use it for planning rather than as an exact record.
Which 1RM formula is best?
No single formula wins for everyone. Epley and Brzycki are the most widely used and agree closely near 10 reps. Pick one and stay with it so that you compare like with like over time.
Why does the calculator reject my repetitions?
Repetitions must be a whole number between 1 and 30, and the weight must be between 1 and 4,000. Decimals in the repetition box are not accepted.
Does it work for any exercise?
The equations were fitted mostly to bench press, squat and similar barbell lifts, but they are used for other exercises too. They are least reliable for isolation exercises and movements that depend on body weight.
References
- Epley B. Poundage chart. Boyd Epley Workout. Body Enterprises, Lincoln, NE, 1985.
- Brzycki M. Strength testing: predicting a one-rep max from reps-to-fatigue. J Phys Educ Recreat Dance. 1993;64(1):88-90.
- 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.
- 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;6:31.
- Haff GG, Triplett NT, eds. Essentials of Strength Training and Conditioning. 4th ed. Human Kinetics, 2016.
Cite this calculator and page
If you use this page in your work, you can cite it as:
Reeliy Editorial Team. (2026). 1-Rep Max Calculator. Reeliy. https://reeliy.com/calculators/one-rep-max-calculator“1-Rep Max Calculator.” Reeliy, 2026, https://reeliy.com/calculators/one-rep-max-calculator.