One-Rep Max (1RM) Calculator
Estimate the most you can lift for a single rep from any set, plus working weights for every rep range.
Enter your details to see your result.
How the one-rep max calculator works
Testing a true one-rep max is tiring and carries injury risk. Instead, we estimate it from a heavy set you’ve already done, by averaging two of the most widely used formulas:
1RM = weight × (1 + reps ÷ 30)1RM = weight × 36 ÷ (37 − reps)Example: 80 kg × 8 reps → Epley 101.3 kg, Brzycki 99.3 kg → estimated 1RM 100.3 kg.
Reading your result
The chart lists percentages of your 1RM and the reps you can typically do at each. Use it to pick weights for your programme:
| Goal | % of 1RM | Reps |
|---|---|---|
| Strength | 80–95% | 1–6 |
| Muscle growth | 65–80% | 6–15 |
| Muscular endurance | 50–65% | 15+ |
Working weights are rounded to the nearest 2.5 kg so they match real plates.
Tips & limitations
- Use a set taken close to failure with good form; estimates are most accurate between 2 and 10 reps.
- Above 12 reps the formulas become unreliable — test a heavier set for a better estimate.
- Re-test every 4–6 weeks to keep your training weights up to date.
- Always use a spotter or safety bars for heavy bench press and squats.
Frequently asked questions
How accurate is a 1RM calculator?
With sets of 2–10 reps taken close to failure, estimates are usually within about 5% of a tested max. Accuracy drops as reps increase.
Which formula is best?
No single formula is best for everyone. Epley tends to read slightly higher and Brzycki slightly lower at moderate reps, so we average them for a balanced estimate.
Should beginners test their one-rep max?
Beginners don’t need to max out. Estimating from a set of 5–8 reps is safer and accurate enough to plan training.
Does the calculator work for all exercises?
It works best for big compound lifts like squat, bench press, deadlift and overhead press. It is less reliable for small isolation exercises.
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These calculators give estimates for general fitness guidance only and aren’t medical advice. Speak to a doctor before making major diet or training changes, especially if you are pregnant, under 18 or have a medical condition.