What Is a One Rep Max (1RM)?
Your one rep max (1RM) is the maximum weight you can lift for a single repetition of an exercise with proper form. It is the fundamental measure of strength and the basis for calculating training loads in virtually every serious strength program. Knowing your 1RM lets you train at the right intensity for your goals: build strength at 85-95%, build muscle at 65-80%, or build endurance at 50-65%.
1RM Formulas Explained
The Epley Formula
1RM = Weight × (1 + Reps ÷ 30)
The Epley formula is the most widely used and validated 1RM equation. Developed by Boyd Epley, it was based on data from Nebraska Cornhuskers athletes. It works best for low-to-moderate rep ranges (1-10 reps).
The Brzycki Formula
1RM = Weight × (36 ÷ (37 - Reps))
Developed by Matt Brzycki at Princeton University, this formula tends to be slightly more conservative than Epley for higher rep ranges (8-12+). Many strength coaches prefer it for hypertrophy-focused programs.
The Lombardi Formula
1RM = Weight × Reps⁰·¹
The Lombardi formula gives slightly higher estimates at low rep ranges and lower estimates at high rep ranges. It is less commonly used but provides a useful third data point.
Worked Example
For a lifter who bench presses 185 lbs for 5 reps:
- Epley: 185 × (1 + 5/30) = 185 × 1.167 = 216 lbs
- Brzycki: 185 × (36/32) = 185 × 1.125 = 208 lbs
- Lombardi: 185 × 5⁰·¹ = 185 × 1.175 = 217 lbs
- Average: 214 lbs
Training Zones Based on Your 1RM
| Zone | % of 1RM | Rep Range | Goal |
|---|---|---|---|
| Max Strength | 90-100% | 1-3 reps | Neural adaptation, peak strength |
| Strength | 80-90% | 3-5 reps | Strength development |
| Hypertrophy | 65-80% | 8-12 reps | Muscle growth, volume accumulation |
| Endurance | 50-65% | 15-25 reps | Work capacity, muscular endurance |
Tips for Safe Max Testing
- Always use a spotter for bench press and squat max attempts.
- Use a power rack with safety pins for squat and bench press.
- Warm up thoroughly with 3-5 ramping sets before your max attempt.
- Rest 3-5 minutes between heavy attempts for full recovery.
- Don't test your max more than once every 4-8 weeks.
- Use this calculator between testing cycles to estimate your 1RM from sub-maximal sets.
Sources and References
- Epley, B. (1985). Poundage Chart: Boyd Epley's Formula for One-Rep Max. National Strength and Conditioning Association Journal.
- Brzycki, M. (1993). Strength Testing: Predicting a One-Rep Max from Reps-to-Fatigue. Journal of Physical Education, Recreation & Dance, 64(1), 88-90.
- Lombardi, V.P. (1989). Beginning Weight Training: The Safe and Effective Way. Wm. C. Brown Publishers.
- Reynolds, J.M., Gordon, T.J., & Robergs, R.A. (2006). Prediction of One Repetition Maximum Strength from Multiple Repetition Maximum Testing. Journal of Strength and Conditioning Research, 20(3), 584-592.