Garage Door Torsion Spring Calculator
Wire size, IPPT and turns for a replacement spring.
Enter your values
Enter the door weight in lb.
Enter the door height in ft.
4in drum = 2in radius
Choose one of: Single spring, Pair of springs.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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
At a glance
| What it does | Wire size, IPPT and turns for a replacement spring. |
|---|---|
| Category | Home & DIY |
| Inputs needed | Door weight, Door height, Drum radius, Number of springs |
| Main output | Winding turns |
| Formula | IPPT = weight × drum radius ÷ turns |
| Cost | Free — no sign-up, no download |
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
- Door weight(lb)
- Enter the door weight in lb.
- Door height(ft)
- Enter the door height in ft.
- Drum radius(in)
- 4in drum = 2in radius
- Number of springs
- Choose one of: Single spring, Pair of springs.
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.
What do I need to enter into the Garage Door Torsion Spring Calculator?
Just 4 values: door weight, door height, drum radius, number of springs. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Garage Door Torsion Spring Calculator work out the answer?
Required IPPT = door weight × drum radius ÷ number of turns; a 7 ft door on 4-inch drums normally needs 7.5 winding turns. It applies the formula IPPT = weight × drum radius ÷ turns and shows the working so you can check each step by hand.
Is the Garage Door Torsion Spring Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.