Guide
How to Measure Garage Door Torsion Springs
How to measure a garage door torsion spring — wire size, inside diameter, length, and wind direction — so your replacement can be sized before the truck rolls. Brought to you by Square One Garage Doors, (303) 994-0375.
Why Bother Measuring a Broken Spring?
When a torsion spring snaps, most homeowners describe it the same way: "my garage door spring broke." That tells a technician the symptom, but not the part. Two springs can look identical and differ by a few thousandths of an inch in wire size — enough to change how the door balances completely.
Four measurements identify a torsion spring completely: wire size, inside diameter, spring length, and wind direction. All four can be taken with a tape measure in about ten careful minutes, and having them means we can quote accurately and arrive with the right spring already on the truck.
This guide exists to make your service call faster, not to turn spring work into a DIY project. Measuring is safe. Winding, adjusting, or unwinding a spring is not — a wound torsion spring stores enough energy to cause severe injury, and that part of the job is always technician work. If you'd rather skip the tape measure entirely, send us photos through the estimate flow and we'll read the numbers for you.
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Measurement One: Wire Size — the 20-Coil Method
Wire size is the thickness of the steel the spring is wound from, and it is the number people get wrong most. Do not try to identify it by eye: common sizes like .207, .2187, and .2253 sit within a few thousandths of an inch of each other.
The standard field method is to measure a row of coils and look the size up on a chart:
1. Pick a clean stretch of spring where the coils sit tight together, away from the cones. 2. Count exactly 20 coils and mark the start of the first and the end of the twentieth. 3. Measure between the marks to the nearest 1/16 inch. 4. Count and measure again to confirm — the count is the part everyone rushes.
Then match your measurement to the standard wire chart:
- .207 wire — 10 coils at 2 1/16 in., 20 coils at 4 1/8 in.
- .2187 wire — 10 coils at 2 3/16 in., 20 coils at 4 3/8 in.
- .2253 wire — 10 coils at 2 1/4 in., 20 coils at 4 1/2 in.
- .2343 wire — 10 coils at 2 5/16 in., 20 coils at 4 5/8 in.
- .2437 wire — 10 coils at 2 7/16 in., 20 coils at 4 7/8 in.
- .250 wire — 10 coils at 2 1/2 in., 20 coils at 5 in.
- .2625 wire — 10 coils at 2 5/8 in., 20 coils at 5 1/4 in.
- .273 wire — 10 coils at 2 3/4 in., 20 coils at 5 1/2 in.
- .283 wire — 10 coils at 2 13/16 in., 20 coils at 5 5/8 in.
These values are the industry-standard measurement, identical across every spring supplier's chart — 20 coils at 4 1/2 inches is .2253 wire no matter who made the spring. If your measurement lands between rows, re-measure before picking the closer one. The spacing between sizes is exactly where sloppy counting shows up.
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Measurement Two: Inside Diameter
The inside diameter (ID) is the open diameter inside the coil — the hole the shaft passes through. Measure straight across it, not the outside of the spring, to the nearest 1/16 inch. Most residential torsion springs are 1 3/4 inches, 2 inches, or 2 5/8 inches.
Before you reach for the tape, check the cones. Many cones carry a stamped or cast number that identifies the ID: 175 means 1 3/4 inches, 200 means 2 inches, 258 means 2 5/8 inches. The stamp confirms one of the four measurements — but only one. Wire size, length, and wind direction still need to be measured.
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Measurement Three: Spring Length
Measure the coiled body of the spring from end coil to end coil, excluding the winding and stationary cones at both ends. The number is only honest when the spring is unwound — a spring under tension stretches, and a stretched measurement undersizes the replacement.
If your spring is broken, this step gets easy: the spring is already fully unwound, so measure both pieces of the coil body and add them together. A broken spring is, oddly, the most measurable spring there is.
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Measurement Four: Wind Direction
Torsion springs come in right-hand wound (RHW) and left-hand wound (LHW), and a typical two-spring door uses one of each. Standing inside the garage looking at the door, the right-hand-wound spring usually sits to the left of the center bracket and the left-hand-wound spring to the right.
Cones follow a color convention — red for right-hand wound, black for left — but paint fades, gets swapped, and is a hint rather than proof. To be certain, look at the end of the coil: if the wire runs upward and away from you clockwise, the spring is right-hand wound. If that check sounds fiddly, it is — a clear photo of each spring end sent through the estimate flow answers it for you.
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What the Measurements Tell a Technician: IPPT
Each of the three physical dimensions moves a value called IPPT — inch-pounds per turn — the torque the spring adds to the shaft for each full turn of winding. A door needs a specific total torque to balance its weight, and that total is IPPT multiplied by the number of turns:
- Thicker wire raises IPPT. Spring rate scales roughly with the fourth power of wire diameter, so a one-step wire change is a much bigger jump than it looks on a ruler.
- A longer spring lowers IPPT. More active coils make the spring less stiff, so each winding turn adds less torque.
- A larger inside diameter lowers IPPT, for the same reason.
This is why the measurements have to be accurate rather than close, and why a thicker spring is never a simple upgrade. Swap in a heavier wire size without re-engineering the length, and the door will fight the opener on the way down and slam on the way up.
It is also why high-cycle springs — the kind rated for 25,000 to 50,000 cycles instead of the standard 10,000 — are usually both thicker and longer than the spring they replace. The larger wire runs at lower stress and lasts longer, but it would overshoot the door's required torque on its own. The added length brings extra active coils, which brings the IPPT back to spec. Length alone does not create cycle life; the combination does, and the finished spring still has to fit the shaft.
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The Six Classic Measurement Mistakes
- Guessing wire size by eye. Measure coils; never estimate. Sizes a few thousandths apart look identical.
- Measuring coils near a cone. Coils spread where the spring meets the cone. Use a clean, tightly wound section.
- Measuring the outside diameter. The spec that matters is the inside diameter.
- Including the cones in the length. Spring length is the coiled body only.
- Measuring length while the spring is wound. A wound spring stretches. Broken springs are actually easier to measure accurately.
- Trusting paint color alone. Confirm wind direction from the coil itself.
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Ready for the Right Spring on the First Visit?
Square One Garage Doors works across the Denver metro, from Aurora and Centennial down through Castle Rock and into Colorado Springs. If your spring is broken — or you've got the four numbers written down and want a firm quote — the fastest path is a call or a few photos.
Call us at 303-994-0375, send photos through the estimate flow, or visit our spring repair service page to see how we handle the replacement itself. For the full step-by-step with photos guidance, see our torsion spring measuring page.