Key Takeaways
- Your leg press 1RM is estimated by averaging the Epley and Brzycki formulas — the two most validated prediction equations.[1]
- Machine angle significantly affects effective load: a 45° leg press only loads ~71% of the weight on the sled.[2]
- Strength standards compare your 1RM relative to bodyweight for meaningful cross-individual comparison.
- The working weight planner generates load suggestions for strength, hypertrophy, and endurance rep ranges.
How 1RM Estimation Works
Directly testing your one-rep max carries inherent risk. Instead, this calculator uses submaximal testing — you enter a weight and the number of reps you completed, and two validated formulas estimate your 1RM:[1]
- Epley formula: 1RM = Weight × (1 + Reps/30)
- Brzycki formula: 1RM = Weight × 36/(37 − Reps)
The calculator averages both estimates for accuracy. Both formulas are most accurate between 2–10 reps; accuracy decreases with higher rep counts. For other strength movements, try our One Rep Max Calculator.
Why Machine Angle Matters
On a 45-degree leg press, gravity only acts through the component of force parallel to the sled's track. The effective load equals the loaded weight multiplied by sin(angle):[2]
- 45° leg press: Effective load = weight × sin(45°) ≈ 71%
- Horizontal press: Effective load = 100% (you push directly against gravity)
- Hack squat (~50°): Effective load ≈ 77%
This means pressing 400 lbs on a 45° sled is roughly equivalent to pressing 284 lbs against gravity. Understanding this helps you compare performance across different machines and track genuine strength progression.
Bodyweight-Relative Strength Standards
Raw weight lifted varies enormously by body size. Relative strength (1RM ÷ bodyweight) provides a fair comparison across different individuals:[3]
| Level | Male (× BW) | Female (× BW) |
|---|---|---|
| Beginner | 1.0× | 0.75× |
| Intermediate | 1.75× | 1.25× |
| Advanced | 2.75× | 2.0× |
| Elite | 3.75× | 2.75× |
For squat-specific comparisons, see our Squat Pyramid Calculator.
Frequently Asked Questions
Sources & References
- Prediction of one repetition maximum from repetitions to fatigue. LeSuer DA, McCormick JH, Mayhew JL. Journal of Strength and Conditioning Research (1997)
- Biomechanical analysis of the leg press exercise. Escamilla RF, et al.. Medicine and Science in Sports and Exercise (2001)
- Strength training standards and norms. Rippetoe M, Kilgore L. Practical Programming for Strength Training (2014)
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Disclaimer: This tool is for informational and personal journaling purposes only. Results are estimates based on published formulas and may vary based on individual factors such as genetics, training history, and measurement technique.