🏋️ 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.