Torsion Spring Calculator for Garage Doors

Garage Door Torsion Spring Calculator

Determine the required IPPT (Inches Per Pound per Turn) and spring turns based on door weight and dimensions.

Spring Specifications

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Understanding Torsion Spring Calculations

A garage door torsion spring is responsible for counterbalancing the weight of the door, allowing it to be opened manually or by an opener with minimal effort. Choosing the wrong spring can lead to a door that is too heavy to lift or one that flies open dangerously fast.

Key Metrics Explained:

• IPPT (Inches Per Pound per Turn): This is the most critical measurement. It represents the amount of torque the spring generates per turn of tension.
• Turns: The number of complete 360-degree rotations the spring must be wound to lift the door to the header.
• Drum Diameter: Most residential doors use a 4-inch drum. Larger drums change the leverage and require different spring rates.

Example Calculation:

If you have a 150 lb door that is 7 feet (84 inches) tall using a standard 4-inch drum:

1. Drum Circumference: 4″ × 3.14159 = 12.56″
2. Turns Required: 84″ / 12.56″ = 6.68 turns + 0.5 (tension) = 7.18 turns.
3. Torque Required: 150 lbs × 2″ (radius) = 300 inch-pounds.
4. Target IPPT: 300 / 7.18 ≈ 41.78 IPPT.

Safety Warning: Garage door torsion springs are under extreme tension. Adjusting or replacing them without proper tools and training can result in severe injury or death. If you are unsure, consult a professional technician.

function calculateTorsion() { var weight = parseFloat(document.getElementById('doorWeight').value); var height = parseFloat(document.getElementById('doorHeight').value); var drumDiam = parseFloat(document.getElementById('drumDiam').value); var safetyTurns = parseFloat(document.getElementById('safetyFactor').value); var resultDiv = document.getElementById('torsionResult'); var output = document.getElementById('outputContent'); if (isNaN(weight) || isNaN(height) || weight <= 0 || height <= 0) { alert("Please enter valid positive numbers for weight and height."); return; } // Calculations var radius = drumDiam / 2; var circumference = drumDiam * Math.PI; var doorTurns = height / circumference; var totalTurns = doorTurns + safetyTurns; // Torque = weight * radius var totalTorque = weight * radius; // IPPT = Torque / Turns var ipptRequired = totalTorque / totalTurns; // Display results resultDiv.style.display = 'block'; output.innerHTML = '

' + 'Target IPPT:' + '' + ipptRequired.toFixed(2) + '' + '

' + '

' + 'Required Turns:' + '' + totalTurns.toFixed(2) + ' turns' + '

' + '

' + 'Total Torque:' + '' + totalTorque.toFixed(1) + ' inch-lbs' + '

' + '

' + 'Drum Circumference:' + '' + circumference.toFixed(2) + ' inches' + '

' + '*When ordering, find a spring or spring combination that sums up to approximately ' + ipptRequired.toFixed(2) + ' IPPT.'; resultDiv.scrollIntoView({ behavior: 'smooth' }); }