What Is a One-Rep Max?
Your one-rep max (1RM) is the maximum weight you can lift for exactly one repetition with good form. It's the gold standard for measuring strength, but it's also a dangerous number to test directly. Attempting a true max lift risks injury, especially for beginners or when fatigue is a factor.
The solution: estimate your 1RM from submaximal lifts. If you can bench press 185 pounds for 5 reps, your actual 1RM is probably somewhere around 210 pounds. Several validated formulas let you calculate this without ever testing a true max.
The Brzycki Formula
The most commonly used 1RM estimation formula is Brzycki's: 1RM = weight × (36 / (37 − reps)). This works best for rep ranges of 1-10. Beyond 10 reps, the formula becomes less accurate because fatigue patterns change.
Example: 100kg for 5 reps → 100 × (36 / 32) = 112.5kg estimated 1RM.
Why 1RM Matters for Training
Once you know your 1RM, you can use percentage-based programming — a cornerstone of periodized training. Common percentages:
- 100% — True 1RM (only tested occasionally)
- 90-95% — Heavy singles and doubles
- 80-85% — Strength range (3-5 reps)
- 70-75% — Hypertrophy range (6-10 reps)
- 60-65% — Volume range (10-15 reps)
- 50-60% — Warm-up and technique work
Use our 1RM calculator to find your max from any rep range.
Important Caveats
1RM estimation formulas are estimates. They assume you've lifted with good form and aren't near muscular failure on the rep count. Individual variation exists — some people are better at singles, others at grinding out high reps. Use the number as a training guide, not a precise measurement. And never ego-lift to "find your max" — the injury risk isn't worth it.