One Rep Max Calculator
Enter any hard set — weight and reps — and get your estimated max plus every training percentage you will ever program with.
Why estimate instead of test?
A true max attempt is a skill and a stressor: it needs a spotter, perfect technique under grinding load, and days of recovery. An estimate from a hard set of 3–6 reps gets within a few percent of the same number with none of that cost, which is why most good programs are written in percentages of an estimated max.
The formulas
We average the two most used equations, which bracket each other nicely:
- Epley: 1RM = weight × (1 + reps ÷ 30)
- Brzycki: 1RM = weight × 36 ÷ (37 − reps)
They agree almost exactly up to 6 reps and drift apart beyond 10 — muscular endurance starts contaminating the estimate, which is why the calculator stops at 12.
Using the percentage table
| Zone | % of 1RM | Reps | Best for |
|---|---|---|---|
| Max strength | 90–100% | 1–3 | Peaking, testing |
| Strength | 80–89% | 3–6 | Getting stronger |
| Hypertrophy | 67–79% | 6–12 | Building muscle |
| Endurance/technique | <67% | 12+ | Volume, learning lifts |
Each lift has its own max. Squat, bench, deadlift and press estimates do not transfer between lifts — run the calculator per exercise, and re-estimate every 4–6 weeks as you progress.
A note for beginners
In your first months, skip max testing entirely. Your estimated 1RM will climb week to week just from technique improving — ride that progress with sets of 5–8 and let the estimate be your scoreboard. Pair it with the protein calculator so the training has something to build with.
Frequently asked questions
How accurate is the estimate?
From a true hard set of 2–6 reps, typically within 2–5% for trained lifters. The set must be honest — stopping three reps short of failure inflates nothing, it deflates the estimate.
Should beginners test their real 1RM?
Not for the first several months. Estimates carry all the programming value with none of the injury risk while technique is still settling.
How often should I recalculate?
Every 4–6 weeks, or whenever a working set suddenly feels light. Programs based on a stale max quietly become too easy.