Leg Press Weight Calculator
The Leg Press Weight Calculator estimates effective weight lifted based on plate load, sled weight, and machine angle. This tool helps weightlifters and physical therapy patients understand the true resistance they are moving against gravity. Whether you're tracking progressive overload, comparing performance with squats, or setting specific rep ranges, this calculator provides accurate data for your training log.
How Effective Weight Is Calculated
Effective weight represents the actual load your muscles work against, taking the machine's incline into account. Because the sled moves on a track rather than straight up, gravity pulls it differently than a free weight. To find this number, we use a standard trigonometric calculation.
Effective Weight = Total Weight × sin(Angle)
Where:
- Total Weight = Weight of plates + Weight of the empty sled
- Angle = The incline of the leg press machine (e.g., 45°)
- Add the weight of the plates loaded onto the machine to the weight of the empty sled.
- Determine the sine of the machine's angle (for a standard 45-degree press, this is roughly 0.707).
- Multiply the total weight by the sine value to see the actual weight you are lifting vertically.
This method accounts for the mechanical advantage provided by the machine, giving you a true measure of your strength.
What Your Effective Weight Means
This number tells you the raw force required to move the sled, stripped of mechanical advantage. It is a standardized way to measure your leg strength regardless of the specific equipment you use. You can use this result to align your lifting with specific training goals.
Muscle Growth (Hypertrophy): Aim for an effective weight that allows you to complete 8 to 12 repetitions. The last few reps should feel very challenging to perform with good form.
Maximal Strength: Use a heavier load that corresponds to 85% to 100% of your max capability. This usually limits you to 1 to 5 repetitions per set.
Endurance or Rehabilitation: Choose a lighter effective weight, roughly 50% to 60% of your maximum. This allows for 15 to 20 smooth repetitions without straining your joints.
Disclaimer: This calculator is for informational purposes only and is not a substitute for professional medical advice. Always consult with a qualified healthcare provider or fitness professional before starting a new exercise program, especially if you have a history of injuries.
Record your effective weight in your workout log to ensure you are progressively overloading your muscles over time.