How to measure heatshrink tubing diameter

Posted by Lucas Smith on

We are often contacted by Customers thinking they have been shipped the wrong-sized heat shrink tubing. When working with the Customer, we often find that they have accidentally, measured the heat shrink tubing incorrectly.

Lets discuss the best way to measure heat shrink tubing to ensure that the correct size is ordered.

To begin, flatten out the heat shrink tubing. Measure the width of the flattened piece with a calliper or ruler, and multiply that figure by 2. Divide this figure by 3.1416 (pi) and the result will be the diameter of your heat shrink tubing.

In the first example picture, below, the heat shrink tubing is measured flat at 1.57" (40mm). Take this number 1.57 (40mm), then multiple by 2. 1.57 (40mm) x 2 = 3.14" (80mm). Then divide it by 3.1416, which comes out to 0.9994" (25.38mm)). Allowing for rounding and measurement errors, this example turns out to be a 1" (25.4mm) nominal diameter piece of heat shrink tubing. This is the correct way to measure.

Calipers measuring flat heatsrink


The second example below is measured measured the same way. The flattened heat shrink’s width is 0.118" (3mm). The math breaks down as follows: 0.118(3mm) X 2 = 0.236 (6mm). Then, 0.236" (6mm) / 3.1416 = 0.075" (1.90mm). Nominal supplied diameter for this tubing is 0.075".

How to measure heat shrink with a ruler

The third example below is showing the wrong way to measure the supplied heat shrink tubing. Please don’t do this, it’s almost impossible to get an accurate measurement this way.

How NOT to measure heat shrink tubing with calipers

If you have any questions on heatshrink measurements or specifications please Contact Us.  

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