Garage Door Torsion Spring Calculator

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Garage Door Torsion Spring Calculator

Calculate IPPT (Inch Pounds Per Turn) and required spring specifications.

Door Weight (lbs)

Door Height (Inches)

Drum Radius (Inches) Standard 4″ Drum (2.0″ Radius) Standard 5″ Drum (2.5″ Radius) Small Drum (1.5″ Radius)

Number of Springs 1 Spring 2 Springs

Calculation Results

Total Torque Required: 0 lbs-in

Total Turns Required: 0 turns

System IPPT Required: 0

IPPT Per Spring: 0

Understanding Torsion Spring Calculations

Choosing the correct torsion spring for your garage door is critical for both safety and the longevity of your garage door opener. When a door is "balanced," the springs provide the exact amount of torque needed to offset the weight of the door, allowing it to be lifted with minimal effort.

DANGER: Torsion springs are under extreme tension. Adjusting or replacing them without proper tools and training can result in severe injury or death. Always consult a professional if you are unsure.

What is IPPT?

IPPT stands for Inch Pounds Per Turn. This is the primary unit of measurement for torsion spring strength. It represents how much torque (in inch-pounds) the spring generates for every full 360-degree turn it is wound.

The Math Behind the Calculation

To find the required IPPT for your garage door, we use the following physical principles:

Total Torque: Calculated by multiplying the door weight by the radius of the cable drum. (Torque = Weight × Drum Radius).
Turns Required: Determined by the door height divided by the circumference of the drum, typically plus one "dead turn" for tension.
System IPPT: Total Torque divided by the Number of Turns.

Example Calculation

If you have a 150 lb door that is 7 feet tall (84 inches) with standard 4-inch drums (2-inch radius):

Torque: 150 lbs × 2″ = 300 Inch-Pounds.
Turns: (84″ / 12.56″ circumference) + 1 ≈ 7.7 turns.
IPPT: 300 / 7.7 ≈ 38.9 IPPT total.
If using 2 springs, each spring would need an IPPT of 19.45.

Important Considerations

When ordering new springs, you must match the IPPT as closely as possible. Changing the wire diameter, inner diameter, or length will change the IPPT. Using a spring with too much IPPT will cause the door to fly open or stay open; too little will make the door heavy and potentially burn out your opener motor.

function calculateSprings() { var weight = parseFloat(document.getElementById('doorWeight').value); var height = parseFloat(document.getElementById('doorHeight').value); var radius = parseFloat(document.getElementById('drumRadius').value); var numSprings = parseInt(document.getElementById('springCount').value); if (isNaN(weight) || isNaN(height) || weight <= 0 || height <= 0) { alert("Please enter valid positive numbers for weight and height."); return; } // 1. Calculate Torque // Torque = Weight * Radius var totalTorque = weight * radius; // 2. Calculate Turns // Drum circumference = 2 * PI * radius // Turns = (Door Height / Circumference) + 1 dead turn var circumference = 2 * Math.PI * radius; var turns = (height / circumference) + 1; // 3. Calculate IPPT // IPPT = Total Torque / Turns var systemIPPT = totalTorque / turns; var perSpringIPPT = systemIPPT / numSprings; // Display Results document.getElementById('resTorque').innerText = totalTorque.toFixed(2) + " lbs-in"; document.getElementById('resTurns').innerText = turns.toFixed(2); document.getElementById('resSystemIPPT').innerText = systemIPPT.toFixed(2); document.getElementById('resPerSpringIPPT').innerText = perSpringIPPT.toFixed(2); // Show the results container document.getElementById('resultOutput').style.display = 'block'; }