One Rep Max Calculator
Estimated maximum single lift from a set, by two published formulas, with common training percentages.
Results
What this tool does
Estimating a one rep max from a working set avoids the risk of actually attempting one, which is the point. The seventy, eighty and ninety percent figures are the loads most strength programmes are written around, so they are usually more useful than the maximum itself.
Formula
1RM = weight × (1 + reps ÷ 30) (Epley)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
w | Weight lifted | kg |
rp | Repetitions | — |
RM | Estimated one-rep max | kg |
RB | Estimated one-rep max | kg |
W8 | Weight lifted | kg |
W7 | Weight lifted | kg |
W9 | Weight lifted | kg |
Worked example
- Weight lifted80 kg
- Repetitions8
- Estimated one-rep max101.33 kg
- Estimated one-rep max99.31 kg
- Weight lifted81.1 kg
- Weight lifted70.9 kg
- Weight lifted91.2 kg
Limitations
- This tool is informational only. It does not diagnose, treat or replace a qualified health professional. Speak to a doctor before making decisions about your health.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.
Frequently asked questions
Why are the two estimates different?
They are different published formulas — Epley and Brzycki — fitted to different data. They agree closely at low repetitions and drift apart above about ten, where all such estimates become unreliable anyway. Take a set to five reps or fewer if you want a meaningful number, and treat either figure as a training guide rather than a target to attempt.