How the 1RM calculator works
Your one-rep max is the heaviest weight you can lift for a single clean repetition. Testing it directly is tiring and risky, so this calculator estimates it from a lighter set using the Epley formula: 1RM = weight × (1 + reps ÷ 30). Lift 80 kg for 8 reps and your estimated 1RM is 80 × (1 + 8/30) ≈ 101 kg.
Getting the most accurate estimate
- Use a set of 10 reps or fewer – the further above 10, the less accurate any formula gets.
- Take the set close to failure with good form, not a warm-up set.
- Use the same lift and equipment each time so results are comparable.
Using percentages of your 1RM
Strength programmes usually prescribe work as a percentage of 1RM: about 85–95% for heavy singles to triples, 70–80% for sets of 5–8 (the hypertrophy sweet spot) and 60% or less for technique and endurance work. Beginners can follow the plan in our strength training for beginners guide.
Frequently asked questions
What is the most accurate 1RM formula?
Epley and Brzycki give very similar results for sets under 10 reps. No formula is perfect; they estimate, they do not measure.
Is it safe to test a true 1RM?
It carries a higher injury risk, especially for beginners and without a spotter. An estimate from a 3–8 rep set is safer and nearly as useful.
How often should I recalculate my 1RM?
Every 4 to 8 weeks, or whenever you hit a new rep record on a lift.
Results are estimates for general information and are not medical advice. See our disclaimer. Talk to a doctor or registered dietitian before making major changes to your diet or training.