What Is a One Rep Max?
Your one rep max (1RM) is the maximum weight you can lift for a single repetition of a given exercise with proper form. It is the foundational measure of absolute strength in powerlifting, weightlifting, and strength-focused fitness training.
Rather than testing your true 1RM in training (which carries injury risk), most athletes use submaximal reps at a known weight to estimate their 1RM. Lifting 100 kg for 5 clean reps, for example, predicts an approximate 1RM of 115–117 kg using the Epley formula. This estimated 1RM then becomes the reference point for all training percentages.
Epley vs Brzycki: Which Formula Is More Accurate?
This calculator uses two of the most validated 1RM prediction formulas:
- Epley (1985): 1RM = weight × (1 + reps ÷ 30). Accurate across a broad rep range (1–10). Best general-purpose formula.
- Brzycki (1993): 1RM = weight × 36 ÷ (37 − reps). Most accurate for low-rep sets (1–6). Less reliable above 10 reps.
In practice, the two formulas agree closely for sets of 1–5 reps and diverge as rep count increases. Using the Epley estimate as a conservative working maximum is standard practice in strength programming. For sets above 10 reps, the prediction becomes less reliable regardless of formula — keep your estimation sets in the 3–8 rep range for best accuracy.
How to Use Your 1RM for Programming
Once you have your estimated 1RM, you can prescribe training loads as percentages. The standard zones for different training goals are:
| Goal | % of 1RM | Rep Range | Sets |
|---|---|---|---|
| Maximum strength | 85–97% | 1–3 reps | 3–5 |
| Strength + hypertrophy | 75–85% | 4–6 reps | 3–5 |
| Hypertrophy | 65–80% | 6–12 reps | 3–4 |
| Muscular endurance | 50–65% | 15–20+ reps | 2–3 |
For beginners and intermediates, training at 70–85% 1RM across sets of 5–10 reps provides an excellent combination of strength and muscle growth stimulus. Advanced athletes and powerlifters cycle through intensity blocks, spending periods at different percentages to develop all strength qualities.
How to Improve Your 1RM
Your 1RM increases through progressive overload — consistently challenging your muscles with slightly more weight, more reps, or higher density over time. The most effective strategies are:
- Train your main lifts 2–3× per week at varying intensities
- Use compound movements (squat, deadlift, bench press, overhead press) as your primary 1RM-building exercises
- Follow a periodised programme that cycles between accumulation (volume) and intensification (load) phases
- Prioritise protein intake of 1.6–2.2 g per kg of body weight to support muscle recovery and growth — use the Protein Calculator
- Hit your calorie target — a slight surplus (200–300 kcal above your TDEE) accelerates strength gains
For a deeper look at training structure, read the Complete Strength Training Guide.
Scientific References: Epley B. (1985). Poundage Chart. Boyd Epley Workout. University of Nebraska Lincoln. — Brzycki M. (1993). Strength Testing — Predicting a One-Rep Max from Reps-to-Fatigue. Journal of Physical Education, Recreation and Dance. 64(1):88–90. — Weakley J, et al. (2021). The Validity and Reliability of Commonly Used Methods to Assess the 1RM. Journal of Strength and Conditioning Research.