One Rep Max Calculator
Estimate your 1RM from a set, plus a full percentage table.
kg
Estimated 1RM
114.6kg
from 5 reps at 100 kg
Epley
116.7 kg
Brzycki
112.5 kg
Training percentages
95% (~1 reps)108.9 kg
90% (~1 reps)103.1 kg
85% (~1 reps)97.4 kg
80% (~1 reps)91.7 kg
75% (~1 reps)85.9 kg
70% (~1 reps)80.2 kg
ShowHide the working
- 1Epley: 100 × (1 + 5/30) = 116.7 kg
- 2Brzycki: 100 × 36/(37−5) = 112.5 kg
- 3Average = 114.6 kg
Formula
Epley: w(1 + reps/30); Brzycki: w × 36/(37 − reps)How it works
Estimates your one-rep max from a set of fewer reps, averaging two well-known formulas, with a percentage table for programming.
Example
100 kg for 5 reps estimates a 1RM of about 115 kg.
For general information only, not medical advice. Individual needs vary — consult a qualified health professional. Attempting a true 1RM without a spotter and warm-up risks injury.
About the One Rep Max Calculator
Estimate your 1RM from a set, plus a full percentage table. It sits in the Health & Fitness section of NWS Calc, a free collection of calculators that run entirely in your browser. There is no signup, no paywall and no tracking — open the page, enter your numbers, get an answer.
Frequently asked questions
- Is the One Rep Max Calculator free to use?
- Yes. Every calculator on NWS Calc is completely free, with no signup, no usage limits and no ads.
- Does my data leave my device?
- No. The One Rep Max Calculator runs entirely in your browser using JavaScript. Nothing you type is uploaded, logged or stored on a server.
- Can I use the One Rep Max Calculator on my phone?
- Yes. The page is fully responsive and works in any modern mobile or desktop browser — there is nothing to install.
- What else is in Health & Fitness?
- BMI, body fat, calories, macros, heart rate and training numbers. You can browse the full Health & Fitness category for related calculators.