Gas Strut Calculator

Determine the Newtons (N) required for your lid, hatch, or door.

The total weight of the object being lifted.

Distance from the hinge to the far edge of the lid.

Usually half of the lid length for uniform lids.

How far along the lid the gas strut will attach.

1 Strut 2 Struts

Calculation Results

Required Force Per Strut:

— N

Total Force Required: — N

Recommended Rating: — N

*Results include a 15% safety margin to account for friction and gas loss over time.

How to Calculate Gas Strut Force

Choosing the correct gas strut (also known as a gas spring) is critical for both safety and functionality. If the force is too low, the lid won't stay open; if it's too high, you might damage the hinges or find it impossible to close the hatch.

The Physics of Gas Struts

The calculation is based on the principle of moments (torque). To calculate the force needed, we use the following formula:

Force (N) = ((W x G x CG) / (D x N)) x 1.15

• W: Mass of the lid (kg)
• G: Acceleration due to gravity (9.81 m/s²)
• CG: Distance from hinge to the Center of Gravity of the lid (mm)
• D: Distance from hinge to the mounting point of the strut on the lid (mm)
• N: Number of struts being used
• 1.15: 15% safety factor

Practical Example

Imagine a heavy storage box lid weighing 40kg that is 1200mm long. You plan to use two struts and mount them 300mm from the hinges. Since the lid is uniform, the center of gravity is at 600mm (half the length).

The math would be: (40kg x 9.81 x 600mm) / (300mm x 2 struts) x 1.15 = 451.26 Newtons. In this case, you would likely purchase 450N or 500N rated struts.

Important Mounting Tips

1. Rod Down: Always mount gas struts with the rod pointing downwards in the closed position to ensure the internal oil lubricates the seals.
2. Mounting Distance: Moving the mounting point (D) closer to the hinge increases the force required significantly. Moving it further away reduces the force required but requires a longer strut stroke.
3. Safety: Always use a safety prop when working under a lid held by gas struts until they are fully installed and tested.

function calculateGasStrut() { var W = parseFloat(document.getElementById('lidWeight').value); var L = parseFloat(document.getElementById('lidLength').value); var CG = parseFloat(document.getElementById('distCG').value); var D = parseFloat(document.getElementById('mountDist').value); var N = parseInt(document.getElementById('numStruts').value); // Validation if (isNaN(W) || isNaN(L) || isNaN(CG) || isNaN(D) || W <= 0 || D <= 0) { alert("Please enter valid positive numbers for all fields."); return; } // G (gravity) = 9.81 // Formula: F = (W * 9.81 * CG) / (D * N) // Adding a 15% safety factor for real-world friction and wear var forcePerStrut = (W * 9.81 * CG) / (D * N); var forceWithSafety = forcePerStrut * 1.15; var totalForceNeeded = W * 9.81 * (CG / D) * 1.15; // Display Results document.getElementById('strutForceResult').innerHTML = Math.round(forceWithSafety) + " N"; document.getElementById('totalForce').innerHTML = Math.round(totalForceNeeded); // Recommendation logic (rounding up to nearest 50N common sizes) var recommended = Math.ceil(forceWithSafety / 50) * 50; document.getElementById('recRating').innerHTML = recommended; } // Initialize calculation once on load window.onload = function() { calculateGasStrut(); };