Heat Shrink Tubing How-To: Measuring the Right Size

This entry is the first in our newest series of How-To Videos.  In these videos, we will show you the proper way to handle many common situations you can come across when dealing with wire and cable.  For instance, in this entry, we show you the proper techniques for measuring your cables before ordering heat shrink tubing to ensure a proper fit.  Check out the rest of the entry for written instructions that follow the video.  If there’s any topic you would like to see explained, let us know!

If you can’t see the heat shrink tubing video above, click here to watch it on our website, or here to see it on our YouTube Channel.


Heat Shrink Tubing is a versatile material that can be used for patching, strengthening, sealing and more.  The best part about it is the ease of installation: when heat is applied, it shrinks.  As straight forward as the name is, however, it can be confusing when it comes to ordering your tubing.  Understanding the product is essential to getting the right measurements before you choose your tubing size.

Most heat shrink tubing specs list a shrinkage ratio in one of two ways: #:# ratio, as in 2:1 or 3:1, or as a percentage.  They mean the same thing: a 2:1 shrinkage ratio means a shrink percentage of 50%, 3:1 means the finished diameter will be just 30% of the expanded diameter.  The higher the number in the ratio, the greater the shrinkage.

To choose a heat shrink tubing size, you need to take some measurements: the diameter of the smallest part you’re covering and the diameter of the widest part.  By knowing how big the heat shrink tubing has to be to start, you can choose how big the tubing has to be at its expanded diameter.  Then, you need to choose tubing that will successfully slide onto your material and shrink down enough for a snug fit.  That is where the smaller measurement comes in handy.

If you don’t measure properly, your heat shrink tubing could slide off if it’s too big or rip if it’s too tight.  The best way to measure is with a caliper, but if you don’t have one a ruler works just fine.  Just make sure you lay the ruler over the material and measure just the diameter.  Don’t use a flexible tape measure and take the circumference!

Once you have the diameter measurements, check out the sizes of the heat shrink tubing you want to purchase and choose one that is 20%-30% larger than the biggest measurement you took.  This could be a connector, or your two measurements might be the same if you’re simply covering a splice.  After you select the proper heat shrink tubing size, make sure you order enough length to cover your project.  Most manufacturers and suppliers will enforce minimums if you only need a small amount, but if you have a big project don’t order too little.  Some heat shrink tubing shrinks longitudinally, so make sure to get a little extra.

Most of the well-known brand name manufacturers of heat shrink tubing, such as Alpha, Raychem, LG, 3M, Sumitomo, will list the dimensions you’ve just determined in their catalogs. Allied Wire & Cable is an authorized distributor of these heat shrink tubing brands as well as other cost-effective heat shrink tubing alternatives.

For more information about the heat shrink tubing products you’ve seen in this demo or any other heat shrink tubing products, contact Allied Wire & Cable today. Call 1-888-325-1788, or visit our website at www.awcwire.com.

About awcwire
Allied Wire & Cable is a value-added manufacturer and distributor of electrical wire and cable, tubing, and more. We are a family owned and operated company, serving a wide range of industries, including the military, automotive, aerospace, and telecommunications markets. Allied is headquartered in Collegeville, PA. Additional locations can be found across the US, in Phoenix, AZ; Bedford, NH; Pewaukee, WI; Rochester, NY, Tampa, FL; and Mt. Juliet, TN. For more information on Allied, visit our main website at www.awcwire.com.

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