How to Identify Your Garage Door Torsion Spring Size
A torsion spring carries the full weight of the door. If the wire size, inside diameter, or length is off by even a fraction, the door will not balance, the opener will strain, and the spring will fail early. Commercial doors run heavier cycles than residential ones, so the margin for error is smaller. Getting the numbers right before you call a supplier or a technician saves a return trip and a second service charge.
What You Need Before You Start
- A 10-inch adjustable wrench or a pair of locking pliers
- A tape measure that reads in 1/16-inch increments
- A digital caliper if you have one — it makes wire size faster and more accurate
- Safety glasses and leather gloves
- A way to mark the shaft so you can reinstall the spring in the same position if you are only measuring
Do not remove the spring until you have the measurements. A broken spring under tension can still turn the shaft violently when the set screws are loosened. If the spring is already broken and the door is on the floor, you can measure it safely on the ground.
Measure Wire Size — the 10-Coil and 20-Coil Methods
Wire size is the thickness of the spring wire itself. It determines the spring's lifting power (IPPT — inch-pounds per turn). The industry standard is to measure 10 or 20 active coils, then divide.
10-coil method: Count 10 coils from the end of the spring. Measure the compressed length of those 10 coils to the nearest 1/16 inch. Divide by 10. Example: 2 1/2 inches ÷ 10 = 0.250 wire size.
20-coil method: More accurate on worn springs. Measure 20 coils, divide by 20. Same example: 5 inches ÷ 20 = 0.250 wire size.
If your measurement falls between two standard sizes, the spring has likely worn down. Round to the nearest standard size. A caliper on a single coil gives a quick check — measure the wire diameter directly, but the coil method accounts for any coating or deformation.
Wire Size and Color Code Reference
| Wire Size (in) | DASMA Color |
|---|---|
| 0.207 | White |
| 0.218 | Yellow |
| 0.225 | Red |
| 0.234 | Brown |
| 0.243 | Green |
| 0.250 | Gold |
| 0.262 | Blue |
| 0.273 | Orange |
| 0.283 | Light Blue |
| 0.295 | Light Green |
| 0.306 | Light Red |
| 0.319 | Tan |
| 0.331 | Purple |
| 0.343–0.625 | Second color cycle repeats from white |
Color fades in sun and chemical exposure. Always verify with the coil measurement — the color is a shortcut, not a specification.
Measure Inside Diameter (ID)
The inside diameter is the hole the shaft passes through. Measure across the inside of the spring body, not the outside.
| Inside Diameter | Typical Shaft Fit |
|---|---|
| 1 3/4 in | 1-inch shaft (most common) |
| 2 in | 1-inch or 1 1/4-inch shaft, bearing-dependent |
| 2 5/8 in | 1 1/4-inch or 1 1/2-inch shaft |
| 3 3/4 in | 1 1/2-inch shaft, higher-cycle doors |
| 5 1/4 in | Heavy industrial doors |
If the spring is on the shaft, you can often read the ID stamped on the winding cone or stationary cone — look for a number like "1.75," "2.0," "2.625," "3.75," or "5.25."
Measure Spring Length
Measure the relaxed length of the spring body only — do not include the cones. If the spring is broken, measure each piece and add them together. If the spring is still wound on the shaft, you cannot get an accurate relaxed length without unwinding it, which is dangerous. In that case, use the wire size and ID to look up the spring in a supplier catalog, or call a technician with those two numbers and the door weight.
Length determines how many turns the spring can take and how much lift it provides per turn. Commercial springs typically run 20 to 60 inches relaxed.
Right-Wind vs. Left-Wind
Stand inside the building looking out at the door. The spring on your left is right-wind (coils clockwise). The spring on your right is left-wind (coils counter-clockwise). On a single-spring system, the spring is usually center-mounted and right-wind.
If you are replacing one spring on a dual-spring door, replace both. The unwound spring has lost cycles and will fail soon. Mismatched springs unbalance the door and overload the opener.
What the Numbers Look Like on a Work Order
A typical commercial spring spec reads: 0.250 x 1.75 x 36 RW — wire size 0.250, ID 1.75 inches, length 36 inches, right-wind. Left-wind is marked LW. Some suppliers list IPPT instead of length; you can convert if you know the door weight and drum size.
When to Stop Measuring and Call a Technician
- The spring is still wound and you do not have winding bars rated for the shaft diameter
- The shaft is bent, the bearings are seized, or the drums are cracked
- The door has been converted from extension to torsion and the hardware looks improvised
- You cannot get a consistent wire-size reading after three tries
- The door is a high-lift or vertical-lift configuration — drum geometry changes the spring calculation entirely
Commercial torsion springs store enough energy to break bones and shatter concrete. If any part of the counterbalance system looks damaged, the safe move is to secure the door in the closed position and wait for a tech.
What to Tell the Supplier or Technician
Give them four numbers: wire size, inside diameter, relaxed length, wind direction. Add the door weight if you know it — check the manufacturer's label on the door or the original spec sheet. If the door has no label, the tech will weigh it on site.
With those four numbers, a supplier can pull the correct spring from stock or wind a custom one. Without them, you are guessing, and a wrong spring costs more in downtime than the service call to measure it properly. CCGDS carries standard and high-cycle commercial torsion springs and replaces them in matched pairs across Metro Vancouver.
Want to understand why the spring failed in the first place? See our guide on why garage door springs break and operators fail.