Garage Door Spring Calculator (Torsion and Extension)
Enter door weight and height, or measure your old spring, to get the exact replacement spec.
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- 150 lb, 84" door
- 0.218" wire size
- 7.50 (30 quarter turns) turns
Cut list: Garage Door Spring Calculator (Torsion and Extension)
- Each of 2 springs0.218" x 1.75" ID x 33-3/4" long
- Spring rate needed20.0 IPPT each (40.1 total)
- Turns to wind7.50 turns (30 quarter turns)
- Cycle rating10,000 cycles, about 6.8 years at 4 a day
- Also fits0.218" x 2" ID x 30" long
- Also fits0.218" x 2.25" ID x 27-1/4" long
- Torque at the drum300 in-lb
- Spring weightAbout 10.1 lb each
- [ ] Torsion springs, 0.218" x 1.75" ID
- [ ] Lift cables
- [ ] Garage door lubricant
- [ ] Bottom brackets
- [ ] Center bearing
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Garage door torsion springs, 150 lb door
A matched pair of 0.218" x 1.75" ID x 34" torsion springs (20.0 IPPT each) for a 150 lb, 84" tall door on 4" drums, rated about 10,000 cycles and wound 7.50 turns (30 quarter turns). Torsion springs store enough energy to break bones; if anything here is unfamiliar, hire a garage door tech.
- Materials
- $120
- Time
- 1 afternoon
- Level
- Advanced
- 1
Decide if this is a DIY job
Torsion spring replacement is one of the most dangerous home repairs. You need proper winding bars, a solid ladder and a methodical approach. Extension springs without safety cables, or doors over 300 lb, are a call to a pro.
- Have a real pair of winding bars
- Door is a standard residential torsion setup
- Willing to stop and call a tech if anything binds
- 2
Measure and order matched springs
Measure the old springs (wire size, inside diameter, length, wind direction) and confirm against the calculator: about 0.218" wire, 2" ID, for a 150 lb door. Always replace both springs together.
- Measure 10 and 20 coil lengths for wire size
- Note left and right wind
- Order a matched pair
- 3
Lock the door down
Close the door, unplug the opener and pull the release, then clamp locking pliers on the track just above a roller on both sides so the door cannot fly up.
- Door closed
- Opener unplugged and disengaged
- Both tracks clamped
- Door
- 150 lb, 84"
- Wire size
- 0.218"
- Turns
- 7.50 (30 quarter turns)
- Est. cost
- $120
8 steps · 7 tools · 5 materials
5 more steps, the full tool list and a shopping list you can check off as you go.
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3/5Garage door torsion springs, 150 lb door
Finished in 1 afternoon · $120 DIY
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How to measure a torsion spring
- Count and measure 10 coils. Push 10 coils tight together and measure them. 2-1/4 in over 10 coils is a 0.225 wire; 20 coils over 4-1/2 in is the same.
- Measure the inside diameter. Read it off the winding cone (most residential springs are 1-3/4 or 2 in) or measure across the inside of the coil.
- Measure the length. Measure the coils only, not the cones, on the unwound spring. On a broken spring, measure both pieces and add them.
- Note the wind. Look at the end of the wire: pointing up and to the right from the near end is right wound. Left-wound springs have red cones and go right of center.
- Enter the numbers. Switch the calculator to Match my old spring for the spec, the door weight it balances, and swaps to another ID or spring count.
How the spring is sized
Turns = door height / (pi x drum diameter) + about 0.8 for the cable. IPPT per spring = door weight x drum radius / (springs x turns). For a 150 lb, 7 ft door on 4 in drums with two springs: turns = 84 / 12.57 + 0.8 = 7.48, IPPT = 150 x 2 / (2 x 7.48) = 20.0. The wire and length then come from the spring rate formula, and the cycle life from the stress in the wire at full wind.
Turns by door height
| Door height | Turns | Quarter turns |
|---|---|---|
| 7 ft | 7.5 | 30 |
| 8 ft | 8.5 | 34 |
| 10 ft | 10.5 | 41 |
| 12 ft | 12.5 | 49 |
| 14 ft | 14.0 | 57 |
Garage door weight chart
| Door | Steel, non-insulated | Steel, insulated | Composite or faux wood | Solid wood |
|---|---|---|---|---|
| 8 x 7 ft | 65 lb | 90 lb | 135 lb | 195 lb |
| 9 x 7 ft | 75 lb | 100 lb | 150 lb | 220 lb |
| 16 x 7 ft | 135 lb | 180 lb | 270 lb | 390 lb |
| 16 x 8 ft | 155 lb | 205 lb | 305 lb | 450 lb |
Torsion spring IPPT chart
| Wire | 1.75" ID | 2" ID | 2.25" ID | 2.625" ID |
|---|---|---|---|---|
| 0.207 | 17.6 | 15.6 | 14.0 | 12.1 |
| 0.218 | 22.7 | 20.1 | 18.1 | 15.7 |
| 0.225 | 26.5 | 23.5 | 21.1 | 18.3 |
| 0.234 | 32.1 | 28.5 | 25.6 | 22.3 |
| 0.243 | 38.6 | 34.3 | 30.9 | 26.9 |
| 0.250 | 44.4 | 39.5 | 35.5 | 30.9 |
| 0.262 | 55.9 | 49.7 | 44.8 | 39.0 |
| 0.273 | 68.4 | 60.9 | 54.9 | 47.8 |
Extension springs
Extension springs are sized by pull weight, not IPPT: each one is rated for about half the door's weight, sold in 10 lb steps and marked with a color code on the end. A 140 lb door takes a pair of 70 lb springs. Buy them as a pair, match the length, and always run a safety cable through each spring.
When to call a pro
Winding a torsion spring stores the door's full weight in a twisted bar of steel. If the bars, set screws or cones are unfamiliar, a garage door tech will swap a pair for about $200 to $350. Opener trouble after the swap is usually balance: see the garage electrical cheat sheet for the opener circuit.
Garage door spring FAQ
How many turns do I wind on a garage door torsion spring?
What size spring for a 16x7 door?
What is IPPT?
How do I measure a garage door spring?
How long do garage door springs last?
Should I replace both springs at once?
How much does it cost to replace garage door springs?
Torsion vs extension springs: what's the difference?
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