Garage Door Torsion Spring Calculator
Wire size, IPPT and turns for a replacement spring.
Enter your values
4in drum = 2in radius
ⓘ Live results
Results
- Winding turns
- 6.68
- Total IPPT needed
- 44.9
- IPPT per spring
- 44.9
- Lift capacity check
- 150 lb
- Safety
- Wind springs with two proper winding bars only — never screwdrivers
Quick answer
Required IPPT = door weight × drum radius ÷ number of turns; a 7 ft door on 4-inch drums normally needs 7.5 winding turns.
IPPT = weight × drum radius ÷ turns
How to use the Garage Door Torsion Spring Calculator
- 1Weigh the door on a bathroom scale with the springs disconnected.
- 2Enter the door height and drum radius.
- 3Choose one spring or a matched pair.
Inputs explained
- Drum radius(in)
- 4in drum = 2in radius
Worked example
Using the values the calculator loads with:
Inputs
- Door weight150 lb
- Door height7 ft
- Drum radius2 in
- Number of springsSingle spring
Results
- Winding turns6.68
- Total IPPT needed44.9
- IPPT per spring44.9
- Lift capacity check150 lb
- SafetyWind springs with two proper winding bars only — never screwdrivers
Frequently asked questions
How many turns does a 7 ft garage door spring need?
About 7.5 turns on standard 400-8 drums — one quarter turn per foot of height plus 7.
Can I replace a torsion spring myself?
Only with proper winding bars and a locked door; a loaded spring stores enough energy to cause serious injury.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.