The Adams 1RM Formula
The Adams formula, introduced by Dr. Gene M. Adams in 1998, is a simple and conservative method for estimating one-repetition max (1RM) using submaximal lifts—typically in the 2 to 10 rep range. It remains a popular choice in both academic and training settings due to its ease of use and emphasis on safety.
Dr. Gene M. Adams: Exercise Physiology Educator
Dr. Gene M. Adams is a respected exercise physiologist and educator known for his practical, science-based approach to strength assessment. As a professor at institutions such as the University of New Mexico, Adams co-authored the widely used Exercise Physiology Laboratory Manual with Dr. William Beam - a foundational text in exercise science programs worldwide. His work focuses on bridging the gap between theory and practice, equipping students, coaches, and athletes with reliable tools for performance testing and safety.
Origin of the Formula
The Adams formula first appeared in the 1998 third edition of the Exercise Physiology Laboratory Manual. It was designed to offer a safe alternative to direct 1RM testing - especially useful in educational settings and for individuals who should avoid maximal lifting. The formula is based on a practical guideline: for each additional repetition beyond one, the lifted weight represents approximately 2% less than the true 1RM. For instance, a 10-rep max typically represents about 80% of your actual max.
The Adams Formula
The Adams formula estimates 1RM with the equation:
1RM = w / (1 - 0.02 × r)
Where:
- w is the submaximal weight lifted
- r is the number of reps performed to fatigue
Example:
If you lift 100 kg for 5 reps:
1RM = 100 / (1 - (0.02 × 5)) = 100 / 0.90 ≈ 111.1 kg
This makes Adams one of the more conservative formulas.
Development and Rationale
Adams developed the formula using the “2% rule,” a long-standing heuristic in strength training that suggests each rep below a true 1RM reduces load by about 2%. The formula avoids complicated regressions or multiple variables, making it ideal for instructional settings, strength evaluations, and general gym use. Unlike Epley or Brzycki, which use slightly higher per-rep multipliers, Adams errs on the side of safety with lower estimates.
Accuracy and Validation
A 2008 study by Mayhew et al. tested the Adams formula in college-aged women performing the bench press. Results showed:
- Pre-training error: +0.7 kg (≈2.9%)
- Post-training error: +1.7 kg (≈5.4%)
- Correlation with actual 1RM: r ≈ 0.90
These results confirm its effectiveness for 2-10 rep sets, especially for compound lifts. However, as with any linear model, accuracy declines at higher reps or in isolation movements. In general, the Adams formula tends to underestimate the actual 1RM.
Lasting Value
The Adams formula continues to be taught in exercise physiology programs and used in strength coaching as a reliable, low-risk estimate of maximum strength. Its simplicity, safety, and academic origins make it a go-to choice for anyone needing a practical 1RM estimation method.
Ready to estimate your 1RM using the Adams formula? Use our 1RM Calculator, explore more Fitness Guides, or Suggest New Tools to enhance MaxCalculator.com!