| Reps | % of 1RM | Weight |
|---|
1RM estimation in the UK gym context
Direct 1RM testing , loading a bar to your absolute maximum and attempting a single lift , is rarely done in commercial UK gyms. The risk of injury without an experienced spotter is significant, and most training programmes use submaximal sets to estimate 1RM instead. British Powerlifting (the UK federation) uses direct 1RM in competition, but training blocks rely on percentage-based work derived from estimated 1RM.
Formula comparison
| Formula | Equation | Best for |
|---|---|---|
| Epley | weight x (1 + reps/30) | General use; most common in UK gyms |
| Brzycki | weight x 36 / (37 - reps) | Accurate for 1-10 reps |
| Lander | 100 x weight / (101.3 - 2.67 x reps) | Powerlifting context |
| Lombardi | weight x reps^0.1 | Higher rep ranges (10+) |
Training zones as % of 1RM
| Zone | % 1RM | Reps | Goal |
|---|---|---|---|
| Maximal strength | 90-100 % | 1-3 | Powerlifting competition prep |
| Strength | 80-90 % | 3-5 | Strength development (British Powerlifting standard blocks) |
| Hypertrophy | 70-80 % | 6-12 | Muscle size; most common range in UK fitness gyms |
| Endurance | 60-70 % | 12-20+ | Muscular endurance; circuit training |
Accuracy and limits
Estimates are least accurate when the rep count exceeds 10, or when the exercise is highly technique-dependent (e.g. Olympic lifts). For best accuracy, use a working set of 3-6 reps at a challenging but controllable weight. The calculator averages multiple formulas to reduce individual formula bias. Results may vary 5-10% from your actual maximum.
Safety: direct 1RM testing requires a competent spotter and should not be attempted alone. Consult a qualified fitness professional before attempting maximal lifts.
For cardio-based training intensity, see the Heart Rate Zones calculator.