RM Conversion Calculator
Instantly convert any working Rep Max (1RM, 3RM, 5RM, 10RM) to any other rep max with scientific precision.
Known Repetition Max
Repetition Maximum Conversion Mechanics
Converting between rep maxes (e.g. 5RM to 1RM, or 10RM to 3RM) operates on the inverse relationship between maximum force production and anaerobic muscular endurance.
Rep Max Conversion Percentage Table
| Rep Max | % of 1RM | Primary Adaptation | Conversion Multiplier to 1RM |
|---|---|---|---|
| 1RM | 100.0% | Maximal Neuromuscular Force | 1.000 |
| 3RM | 92.5% | Functional Strength & Density | 1.081 |
| 5RM | 85.7% | Strength-Hypertrophy Pivot | 1.167 |
| 8RM | 78.5% | Myofibrillar Hypertrophy | 1.274 |
| 10RM | 75.0% | Sarcoplasmic Hypertrophy | 1.333 |
| 12RM | 70.0% | Muscular Endurance & Glycogen | 1.428 |
Formula Step-by-Step: Converting 5RM to 3RM
Suppose you know your 5RM is 120 kg, and want to know your estimated 3RM:
- Derive Estimated 1RM:
1RM = 120 × (1 + 5 / 30) = 120 × 1.167 = 140.0 kg. - Derive 3RM from 1RM: At 3 reps, the standard intensity is 92.5%:
3RM = 140.0 × 0.925 = 129.5 kg. - This direct two-step mathematical pipeline prevents compounding rounding errors.
Frequently Asked Questions
Answers to common questions regarding Rep Max conversions and program design.
Using the validated Epley formula: 1RM = 5RM Weight × (1 + 5 / 30). This equates to multiplying your 5RM by 1.167. A 100 kg 5RM corresponds to a 116.7 kg 1RM.
Yes. The calculator first resolves your 10RM to a standardized 1RM baseline (multiplying by 1.333), then scales the load to the 3RM intensity coefficient (0.925). For example, an 80 kg 10RM becomes a 98.6 kg 3RM.
Sets above 10 reps introduce cardiovascular endurance, lactic acid accumulation, and mental fatigue as confounding factors. For maximum conversion accuracy, base calculations on sets of 2 to 8 repetitions.