Free Heat Shrink Tubing Size Calculator
Select the optimal nominal heat shrink tubing diameter and shrink ratio (2:1, 3:1, 4:1) to fit over connectors and clamp down tightly on cables.
📏 Bundle & Connector Diameters
📊 Recommended Tubing Size
Recommended Tools & Equipment
Tested hardware and components for high reliability
The 80/20 Rule of Heat Shrink Tubing
To achieve a watertight, strain-relieved seal without splitting the tubing, adhere to the 80/20 Rule:
20% Expansion Clearance
The expanded inside diameter (as supplied) should be at least 20% larger than your largest connector plug to ensure it slips over easily without snagging sharp metal pins.
20% Remaining Shrink Buffer
Never choose tubing whose fully recovered diameter exactly equals the wire diameter. Heat shrink must retain at least 10% to 20% unused shrink capacity to maintain active radial compression pressure against the cable jacket.
Frequently Asked Questions
Why should I use 3:1 adhesive-lined dual wall heat shrink?
Dual-wall tubing contains an inner layer of hot-melt adhesive that liquefies when heated, filling all voids between wires to provide a 100% waterproof, corrosion-proof IP68 seal for automotive and marine wiring.
Does heat shrink tubing shorten when heated?
Yes. Polyolefin heat shrink experiences 5% to 10% longitudinal shrinkage (it shrinks in length as its diameter contracts). Always cut your tubing slightly longer than your target splice.
What temperature is needed to shrink polyolefin tubing?
Standard single-wall polyolefin begins shrinking around 90°C (194°F) and fully recovers at 120°C (250°F). Adhesive-lined dual-wall requires roughly 110°C to 135°C to fully melt the internal glue.