Shrink ratio
The shrink ratio indicates how much heat shrink tubing contracts when heated. This is important when choosing the right type of shrink tubing. Different types of heat shrink tubing have different shrink ratios — these are listed in the product name as “2:1” (2 to 1), “3:1” (3 to 1), and so on. All available variants of these types (different sizes, shapes, and packaging options) share the same shrink ratio.
Available shrink ratios
Heat shrink tubing is available in six different shrink ratios:
The shrink ratio represents the relationship between the inner diameter of the tubing before and after shrinking. These are indicated as the "as supplied" inner diameter and the "after shrink" inner diameter. For example, if a heat shrink tube has an inner diameter of 30 millimeters before shrinking, the resulting inner diameters after shrinking are as follows:
- 1.5:1 → inner diameter after shrink: 20 mm
- 2:1 → inner diameter after shrink: 15 mm
- 2.5:1 → inner diameter after shrink: 12 mm
- 3:1 → inner diameter after shrink: 10 mm
- 4:1 → inner diameter after shrink: 7.5 mm
- 6:1 → inner diameter after shrink: 5 mm
How to choose the right shrink ratio
To select the right shrink ratio, first determine the diameter of the object the tubing will be used on — for example, the diameter of a cable. Then choose a shrink tube with a post-shrink inner diameter that is slightly smaller than the diameter of the object. For example:
Suppose you have a cable with a diameter of 0.5 millimeters. Then choose a heat shrink tube with an inner diameter after shrink of 0.4 millimeters. If the shrink tube has a 3:1 shrink ratio, the pre-shrink diameter needs to be 1.2 millimeters (0.4 × 3).
Need help determining the right size and shrink ratio? Feel free to contact our advisors — they’ll be happy to assist you.
