How to Check Torsion Spring Size Before You Order (A Buyer's Checklist)

Measure Four Things, Write Them Down, Measure Again

If you're replacing a torsion spring — garage door, industrial counterbalance, whatever — here's the whole answer in one sentence: you need wire diameter, inside diameter, overall length, and wind direction (left-hand or right-hand). Get any one of those wrong and the spring either won't fit or won't counterbalance the load. Wire diameter is the one people screw up most, because a 0.010-inch difference isn't visible to the eye but changes the torque rating by roughly 10–15%.

That's it. If you only read this far, you have what you need. What follows is why I know that, what happens when you skip a step, and when you should stop trying to measure it yourself.

Why You Should Probably Trust This

I'm an office administrator for a 180-person company. I handle facilities and MRO purchasing — roughly $340,000 a year across 14 vendors. Torsion springs aren't my main category, but they show up: overhead doors at two warehouse bays, a counterbalance in the shipping dock lift, and a couple of spring check valves on the air compressor lines that I order as spares.

In early 2024, I ordered what I thought were matching replacement springs for the bay 3 overhead door. The door came down hard on a pallet jack. Nobody was hurt (thankfully), but we paid $1,100 in labor, an emergency service call, and a replacement spring that we then had to return because I'd guessed the wire gauge off a photo. I still kick myself for that one.

The Four Measurements, In Order

1. Wire diameter

Use digital calipers, not a ruler. Measure at three points along the coil and average them. Standard garage door torsion springs run anywhere from 0.1875" to 0.375" wire diameter, and manufacturers spec in increments of 0.0001". A cheap pair of calipers costs $25 on Amazon and will save you a return shipping fee every single time.

What I mean is, the wire diameter is not just about physical fit — it's directly tied to how much torque the spring produces at a given number of turns, along with the coil count and inside diameter. Change one number and the door balance changes.

2. Inside diameter (ID)

Measure the inside of the coil, not the outside. Standard IDs are 1-3/4" and 2" for residential, 2-5/8" for heavier commercial doors. If the spring has a worn or stretched coil, measure near the middle, not the ends.

3. Overall length of the coiled section

Not the whole assembly — just the coil body, without the cones or winding bars attached. Some suppliers quote "length" as the relaxed coil length; others quote it installed. Always ask. I've been burned by this twice, and now I write "relaxed coil length in inches" in every RFQ.

4. Wind direction

This is the one that trips everybody up. Stand facing the spring from the side. If the wire wraps away from you at the top of the coil when you trace it counterclockwise, it's a left-hand wind. If it wraps toward you, it's right-hand. When in doubt, lay the spring next to a known reference or photograph it from two angles and send it to your supplier.

Roughly 60% of torsion spring returns come from wrong wind direction or wire diameter, according to conversations I've had with three different spring suppliers over the past two years. None of them could give me a documented figure, so treat that as a vendor-side estimate, not a published stat.

The Decision That Kept Me Up For A Week

After the bay 3 incident, I went back and forth between ordering OEM replacements through the door manufacturer and going through a general spring supplier. OEM offered a documented fit and a warranty tied to the door; the general supplier offered about 30% savings and a faster lead time. Ultimately I chose OEM for the two high-traffic doors and the general supplier for the rarely-used dock lift, because if the cheap one failed, the consequences were small. That split worked for us. It might not for you.

Where Spring Check Valves Fit In

Different animal, same principle. A spring check valve uses a light compression spring to hold the disc closed against low back-pressure. If you're replacing one on an air compressor pump or a hydraulic line, you usually don't measure the spring — you replace the whole valve body, because the spring rating is matched to the cracking pressure and flow characteristics of the valve. Trying to source just the spring inside a check valve is a waste of time for a non-engineer. Buy the valve.

Same logic with air compressor pumps. The valve springs inside the head are tuned to the pump's compression ratio. Order the OEM service kit, not a generic spring.

When Not To DIY This

A few honest limits:

• If the door or the load has more than two springs, call a technician. The torque and cycle-life math gets real, and mismatched springs on the same shaft will eat themselves.
• If you can't safely wind down the existing spring, stop. Torsion springs under load carry serious stored energy. Two people in my industry network have been to urgent care over this. I'm not exaggerating.
• If the manufacturer's label is still on the spring or the door frame, read it first. It usually lists wire diameter, ID, and length. That saves you three of the four measurements.
• If the spring is more than 10 years old and you're replacing one side, replace both. They wear together, and a new-and-old pair will unbalance.

Pricing reference for what to expect: residential torsion springs typically run $30–65 each for standard sizes, and commercial-grade springs run $60–180 depending on wire diameter and cycle rating (based on publicly listed supplier catalogs, early 2025; verify current pricing with your vendor — steel prices moved a lot in 2024).

If you're an admin buyer like me and not an engineer, the four-measurement checklist plus a photo from two angles is genuinely enough to get the right part 95% of the time. The other 5% is why you keep the technician's number on speed dial.