1 Rep Max Calculator
Enter a weight and the reps you hit, and we'll estimate your one-rep max (1RM) plus the training percentages to program around it. No max-out attempt required.
Average of the Epley & Brzycki formulas.
Training percentages
Use these to load your working sets. Strength work usually lives in 80–90%; hypertrophy around 65–80%.
| % of 1RM | Weight | Typical reps |
|---|
How the 1RM estimate works
Your one-rep max is the heaviest weight you could lift for a single rep with good form. Instead of risking a true max attempt, you can estimate it from a lighter set. This calculator averages two proven formulas:
- Epley: 1RM = weight × (1 + reps / 30)
- Brzycki: 1RM = weight × 36 / (37 − reps)
Averaging them smooths out the quirks each formula has at different rep ranges, so you get a steadier number to train from. Estimates are sharpest in the 2–6 rep range.
Frequently asked questions
How accurate is a 1-rep-max calculator?
Estimates are most accurate in the 2–6 rep range, usually within about 5–10% of a true max. Above 10 reps, accuracy drops because endurance and technique start to matter more than raw strength.
Which formula does this calculator use?
It averages the two most widely used formulas — Epley and Brzycki — which keeps the estimate stable across different rep ranges instead of relying on a single equation.
How do I use the percentage table?
Once you know your estimated 1RM, the table shows how much weight to load for a given percentage. Most strength programs prescribe work in the 70–90% range; hypertrophy work tends to sit around 65–80%.
Should I actually test my 1-rep max?
You don't need to. Testing a true max is taxing and carries injury risk, especially without a spotter. Estimating from a set of 3–5 reps gives you the numbers you need to program your training safely.
Programming around these numbers? See our workout plans and gear reviews.