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Calculate IPPT, wire size, coil count, cycle life, and find the perfect replacement spring for your garage door. Built by Calgary’s #1 rated garage door company with 20+ years of experience.
Calculate garage door spring specifications and find the right replacement
IPPT: IPPT = (E × d⁴) / (10.8 × Dm × Na) where E = 28,500,000 psi
System IPPT (Matched): IPPT × Number of Springs
System IPPT (Mismatched): Spring1 IPPT + Spring2 IPPT
Required IPPT: (Weight × Drum Radius) / (Turns × Springs)
This free torsion spring calculator helps homeowners, technicians, and DIY enthusiasts determine the correct garage door spring specifications. Whether you’re replacing a broken spring, converting to a different spring setup, or calculating requirements for a new door installation, this tool provides accurate results using industry-standard engineering formulas.
The calculator was developed by Calgary Garage Door Fix, drawing on data from over 32,000 garage door repairs completed since 2019. Every formula has been verified against real-world installations across Calgary’s demanding climate conditions.
IPPT (Inch-Pounds Per Turn) is the critical measurement for garage door springs. It tells you how much lifting torque a spring provides for each turn it’s wound. The formula is:
IPPT = (E × d⁴) / (10.8 × Dm × Na)Where:
Notice that wire diameter is raised to the fourth power. This means small changes in wire size dramatically affect lifting power. A spring with 0.2343″ wire produces roughly 18% more IPPT than one with 0.2253″ wire—even with identical ID and length.
To determine what spring you need, calculate the required IPPT based on your door:
Required IPPT = (Door Weight × Drum Radius) / (Winding Turns × Number of Springs)For a typical setup with 4″ drums (2″ radius):
For a 180 lb door, 7 feet tall, with 2 springs:
The calculator then searches for spring combinations (wire size, ID, length) that produce approximately 23.44 IPPT each.
Garage door springs have a finite lifespan measured in “cycles” (one cycle = one open + one close). The cycle rating depends on the stress level the spring operates under:
| Cycle Rating Operating Stress (psi) | Expected Lifespan | Best For |
|---|---|---|
| 10,000 cycles ~242,000 psi | 7-10 years | Average residential use (3-4 cycles/day) |
| 15,000 cycles ~220,000 psi | 10-12 years | Above-average use |
| 20,000 cycles ~210,000 psi | 12-15 years | Busy households |
| 25,000 cycles ~200,000 psi | 15-20 years | High-use residential, light commercial |
| 50,000 cycles ~175,000 psi | 25+ years | Commercial applications |
Higher cycle ratings require longer springs with more active coils to reduce per-coil stress. This calculator factors in cycle life when making spring recommendations.
Calgary’s extreme temperature swings (from -30°C in winter to +30°C in summer) accelerate metal fatigue in garage door springs. We typically see 10-15% shorter spring lifespans here compared to moderate climates. This calculator accounts for these conditions in its cycle life estimates.
To use this calculator effectively, you’ll need three measurements from your existing spring. Always measure with the door fully closed (spring unwound) for accuracy.
Measure the inside diameter of the spring coils—the empty space in the center. This is NOT the torsion bar diameter. Common residential sizes:
The most accurate method:
Example: 20 coils measuring 4.374″ total = 0.2187″ wire size
Measure the overall length of the spring body (excluding the winding and stationary cones). Round to the nearest half-inch.
⚠️ Safety Warning: Torsion springs are under extreme tension and can cause serious injury. If you’re uncomfortable measuring springs or your door has a broken spring, call a professional. Calgary Garage Door Fix offers same-day service: (403) 990-9536
While this calculator helps you understand spring specifications, garage door spring replacement is dangerous and should be performed by trained technicians. Torsion springs store enough energy to cause serious injury if mishandled.
Calgary Garage Door Fix offers same-day spring replacement throughout Calgary and surrounding areas:
Call: (403) 990-9536 | Learn more about spring replacement →
ABOUT THE AUTHOR
Stan Klugman | Founder, Calgary Garage Door Fix
Stan has over 15 years of experience in the garage door industry and has personally overseen more than 32,000 residential and commercial repairs across Calgary. Calgary Garage Door Fix is a BBB-accredited business and holds registered trademarks in both Canada (TMA1352082) and the United States (98141232).