Knowing how much you could lift for a single repetition is the basis of most strength programmes, but testing it directly is hard on the body and risky without a spotter. A well-established alternative is to lift a lighter weight for several repetitions and estimate the max from the result. Researchers have published a number of equations for this, and they agree closely at low rep counts. This calculator applies six of them to your set and shows the training loads that correspond to common percentages of your estimated max.
The result is an estimate. How closely it matches a true max depends on the exercise, your experience and how hard the set really was.
How to use the one rep max calculator
- Enter the weight you lifted in kilograms or pounds.
- Enter the number of reps you completed with good form, taking the set to or close to failure.
- Compare the six formulas. They are similar below about 6 reps and spread out as reps increase.
- Use the average for programming, and the percentage loads for planning your sets.
One rep max formulas
W is the weight lifted and r the number of repetitions.
Brzycki: W × 36 ÷ (37 − r)
Lombardi: W × r0.10
O’Conner: W × (1 + 0.025 × r)
Mayhew: 100 × W ÷ (52.2 + 41.9 × e−0.055 r)
Wathan: 100 × W ÷ (48.8 + 53.8 × e−0.075 r)
Sources: Epley B, Poundage Chart, Boyd Epley Workout, University of Nebraska, 1985; Brzycki M, Strength testing: predicting a one-rep max from reps-to-fatigue, JOPERD 1993;64:88–90; Lombardi VP, Beginning Weight Training, 1989; O’Conner B, Simmons J, O’Shea P, Weight Training Today, 1989; Mayhew JL et al., J Appl Sport Sci Res 1992;6:200–206 (bench press); Wathan D, Load assignment, in Essentials of Strength Training and Conditioning, 1994. Their accuracy was compared by LeSuer et al., J Strength Cond Res 1997;11:211–213.
Worked example
You bench press 100 kg for 5 repetitions.
- Epley: 100 × (1 + 5 ÷ 30) = 116.7 kg
- Brzycki: 100 × 36 ÷ (37 − 5) = 112.5 kg
- Lombardi: 100 × 50.10 = 117.5 kg
- O’Conner: 100 × (1 + 0.025 × 5) = 112.5 kg
- Mayhew 119.0 kg, Wathan 116.6 kg
- Average: 115.8 kg, about 255 lb.
Training loads as a percentage of 1RM
For the example lifter, using the average estimate of 115.8 kg.
| % of 1RM | Load for the example lifter (kg) | Load (lb) |
|---|---|---|
| 95% | 110.0 kg | 243 lb |
| 90% | 104.2 kg | 230 lb |
| 85% | 98.4 kg | 217 lb |
| 80% | 92.6 kg | 204 lb |
| 75% | 86.8 kg | 191 lb |
| 70% | 81.1 kg | 179 lb |
| 65% | 75.3 kg | 166 lb |
| 60% | 69.5 kg | 153 lb |
| 50% | 57.9 kg | 128 lb |
How many reps match each percentage
The percentage of 1RM you are lifting when you reach failure at a given rep count, according to three of the formulas.
| Reps to failure | % of 1RM (Brzycki) | % of 1RM (Epley) | % of 1RM (Lombardi) |
|---|---|---|---|
| 1 | 100% | 97% | 100% |
| 2 | 97% | 94% | 93% |
| 3 | 94% | 91% | 90% |
| 4 | 92% | 88% | 87% |
| 5 | 89% | 86% | 85% |
| 6 | 86% | 83% | 84% |
| 7 | 83% | 81% | 82% |
| 8 | 81% | 79% | 81% |
| 9 | 78% | 77% | 80% |
| 10 | 75% | 75% | 79% |
| 11 | 72% | 73% | 79% |
| 12 | 69% | 71% | 78% |
Getting a good estimate
- Use a set of 2 to 8 reps. Accuracy falls as the number of repetitions rises.
- Be honest about failure. If you could have done three more reps, the estimate will be too low.
- Do not mix exercises. A bench press estimate does not carry over to a squat. Each lift has its own max, and lifts that use more muscle mass tend to be harder to predict.
- Re-test now and then, because strength changes with training.
For protein needs to support training see the Protein Intake Calculator. Lift-specific tools include the Bench Press Max Calculator, Squat Max Calculator and Deadlift Max Calculator, and the lifting-strength-calculator compares your totals with standards.
This page is for information only and is not medical advice. If you have a heart condition, take medicines that affect heart rate, or are new to exercise, check with a doctor before starting a training plan.
Sources
- Epley B. Poundage Chart. Boyd Epley Workout. University of Nebraska, Lincoln, 1985.
- Brzycki M. Strength testing — predicting a one-rep max from reps-to-fatigue. J Phys Educ Recreat Dance 1993;64:88–90.
- Mayhew JL, Ball TE, Arnold MD, Bowen JC. Relative muscular endurance performance as a predictor of bench press strength in college men and women. J Appl Sport Sci Res 1992;6:200–206.
- 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. J Strength Cond Res 1997;11:211–213.
Frequently asked questions
What is a one rep max?
Your one rep max (1RM) is the heaviest weight you can lift for a single repetition with correct form. It is the standard measure of maximal strength and the basis for setting training loads as a percentage of your max.
Which 1RM formula is most accurate?
It depends on the lift and the number of reps. A comparison of the equations for the bench press, squat and deadlift (LeSuer et al., J Strength Cond Res 1997;11:211–213) found that accuracy differed by lift and that no single equation was best for all three. That is why the calculator shows six and an average.
Why is the estimate less reliable at high reps?
Fatigue, technique and conditioning matter more as sets get longer, so the link between reps and maximal strength weakens. Estimates from sets of 10 or fewer are far more dependable than those from sets of 15 to 20, and some formulas stop working above about 36 reps.
Is it safe to test a true one rep max?
It carries more risk than submaximal training, especially for beginners. Use a spotter or safety bars, warm up thoroughly, and consider estimating your max from a 3 to 5 rep set instead of attempting it.
How do I use the percentages?
Most programmes prescribe work as a percentage of 1RM, for example 5 sets of 5 at 80 percent. Multiply your estimated 1RM by the percentage to get the load, as shown in the table, then adjust based on how the sets feel.