What the 1RM is and what it is for
The 1RM, or one-rep max, is the heaviest weight you can lift once with good technique on an exercise. It is useful for programming, because many routines set the load as a percentage of 1RM (for example, 5 sets at 80%), and for tracking your strength without testing a true max, which is riskier and far more tiring.
How the 1RM is estimated from a single set
The calculator uses the average of two of the most widely used formulas:
- Epley (1985): 1RM = weight × (1 + reps / 30)
- Brzycki (1993): 1RM = weight × 36 / (37 − reps)
Both give very similar results with few reps and drift apart as reps go up. That is why it only accepts sets of 1 to 10 reps: in the study by Reynolds and colleagues (2006), with 70 people aged 18 to 69 on the bench press and leg press, the 5-rep set predicted 1RM best, and the authors advise against using more than 10 reps with this kind of equation.
| Formula | Estimated 1RM |
|---|---|
| Epley | 116.5 kg |
| Brzycki | 112.5 kg |
| Average (what the calculator gives) | 114.5 kg |
Which set to use for the estimate
- A set of 3 to 6 reps with a challenging weight, until you cannot do another rep with good technique.
- Warm up first with two or three lighter ramp-up sets.
- Always use the same exercise and technique, or the results will not be comparable.
Training loads by percentage of 1RM
With your 1RM, the calculator gives the load for each percentage and the approximate reps it allows according to the Epley formula. Treat them as a guide: the meta-analysis by Nuzzo and colleagues (2024), with 269 studies and more than 7,000 people, found substantial variation between individuals, and more reps on the leg press than on the bench press at the same percentage. Sex, age and training status barely changed that relationship.
| % of 1RM | Approximate reps |
|---|---|
| 95% | 2 |
| 90% | 3 |
| 85% | 5 |
| 80% | 8 |
| 75% | 10 |
| 70% | 13 |
| 65% | 16 |
| 60% | 20 |
To decide how close to failure to take each set, see RIR and RPE; to add load week by week, progressive overload; and if you are starting out, the beginner strength routine.
