One Rep Max (1RM) Calculator
Your one-rep max (1RM) is the heaviest weight you can lift for a single repetition of an exercise. Testing it directly is risky and demanding, so most lifters estimate it from a submaximal set. This calculator uses the Epley formula to predict your 1RM from the weight and number of reps you completed, and then builds a percentage table so you can pick the right load for strength, hypertrophy, or endurance work.
Your estimated 1RM
1RM percentages
This is an estimate using the Epley formula; it does not replace a trainer’s judgment. Warm up properly before attempting maximal loads.
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How it works
Epley formula: 1RM = weight × (1 + reps / 30). For a single rep the weight itself is your 1RM. The table then applies standard training percentages to that estimate: 1 rep at 100%, 2 reps at 95%, 3 reps at 90%, 5 reps at 87%, 8 reps at 80%, 10 reps at 75% and 12 reps at 70%. Lifting 100 kg for 10 reps gives an estimated 1RM of about 133.3 kg.
1RM percentage table
Once you know your 1RM, you can derive the approximate load for any number of repetitions. These percentages come from the standard strength charts (Brzycki and Epley coefficients) and are the basis for programming sets. The last column shows the weight that matches each target if your 1RM were 100 kg; scale those values to your own maximum.
| Repetitions | % of 1RM | Load (100 kg 1RM) |
|---|---|---|
| 1 | 100% | 100 kg |
| 2 | 95% | 95 kg |
| 3 | 90% | 90 kg |
| 4 | 88% | 88 kg |
| 5 | 87% | 87 kg |
| 6 | 85% | 85 kg |
| 8 | 80% | 80 kg |
| 10 | 75% | 75 kg |
| 12 | 70% | 70 kg |
| 15 | 65% | 65 kg |
Using your 1RM to program training
The percentage of your 1RM defines the stimulus. To build maximal strength you train heavy, between 85 and 100% (1 to 5 reps) with long rests of 3 to 5 minutes. Hypertrophy (muscle growth) is targeted in the 70 to 85% range with 6 to 12 reps and pauses of 1 to 2 minutes. Muscular endurance uses light loads below 70% and sets of 15 or more reps. Reassess your 1RM every 4 to 8 weeks.
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Preguntas frecuentes
- What is a one-rep max (1RM)?
- It is the maximum weight you can lift for a single, complete repetition of a given exercise with good form. It is the most common benchmark of pure strength and is used to prescribe training loads as a percentage of that maximum.
- What is the Epley formula?
- The Epley formula estimates your 1RM as weight × (1 + reps / 30). It is one of the most widely used equations because it is simple and accurate for sets in roughly the 1–10 rep range.
- How accurate is an estimated 1RM?
- Estimates are most reliable when the set is close to failure and uses about 10 reps or fewer. As the number of reps grows, the prediction drifts, because endurance and fatigue play a bigger role than raw strength. Treat the number as a guide, not an exact figure.
- What are the 1RM percentages for?
- Training programs are often written as a percentage of your 1RM. Heavy sets near 85–100% build maximal strength, the 70–85% range favors hypertrophy, and lighter loads below 70% build muscular endurance. The table gives you a ready-made load for each rep target.
- Is it safe to test my real 1RM?
- Testing a true 1RM is demanding on joints and the nervous system and should only be attempted by experienced lifters, well warmed up, with a spotter and proper technique. For most people, estimating from a submaximal set is safer and accurate enough.