🏋️ One-Rep Max (1RM) Calculator
Enter a weight and the reps you managed to estimate your one-rep max — averaged across three proven formulas, with a percentage table for programming.
Estimated 1-rep max
115.5 kg
Epley 116.7 · Brzycki 112.5 · Lombardi 117.5 kg
| Reps | % of 1RM | Weight |
|---|---|---|
| 1 | 96.8% | 111.8 kg |
| 2 | 93.8% | 108.3 kg |
| 3 | 90.9% | 105 kg |
| 5 | 85.7% | 99 kg |
| 8 | 78.9% | 91.2 kg |
| 10 | 75% | 86.7 kg |
| 12 | 71.4% | 82.5 kg |
| 15 | 66.7% | 77 kg |
Averages the Epley (w × (1 + reps⁄30)), Brzycki (w × 36⁄(37−reps)) and Lombardi (w × reps^0.1) estimates. Accuracy drops above ~10 reps. Estimates only — lift within your ability and use a spotter. 🔒 In your browser.
How the one-rep max (1rm) calculator works
A one-rep max (1RM) is the most you could lift once. Rather than testing it directly (which is risky), the tool estimates it from a lighter set: the Epley formula is weight × (1 + reps⁄30), Brzycki is weight × 36⁄(37 − reps), and Lombardi is weight × reps^0.1. It averages the three and builds a table of the weights corresponding to each rep count.
These estimates are most accurate for sets of about 1–10 reps; beyond that they tend to overestimate. Use the percentage table to pick training loads — e.g. 5×5 work is often around 80–85% of 1RM. Always warm up, lift within your ability and use a spotter.
Frequently asked questions
How do I calculate my one-rep max?
Do a set to near-failure at a known weight, then apply a formula. Epley: 1RM = weight × (1 + reps⁄30). For 100 kg × 5 reps that's 100 × (1 + 5⁄30) ≈ 116.7 kg. This tool averages Epley, Brzycki and Lombardi.
Which 1RM formula is most accurate?
No single one is best for everyone — they agree closely at low reps and diverge as reps rise. Averaging several (as this tool does) is more robust than relying on one, and all are estimates rather than a true test.
What percentage of 1RM should I train at?
It depends on the goal: strength work is often 80–95% of 1RM for low reps, hypertrophy around 65–80%, and endurance below 65%. The percentage table shows the weight for each rep count.
Is it safe to test my actual 1RM?
A true 1RM test is demanding and carries injury risk, especially without experience or a spotter. Estimating from a submaximal set is safer and accurate enough for programming for most lifters.
Why is the estimate less accurate at high reps?
The formulas are calibrated for low-rep sets. Past about 10–12 reps, fatigue, technique and endurance vary so much between people that the linear/curved models overestimate the true max.