How Much
Heat Shrink Do
I Need?
Allow about 2″ of tubing per butt splice, 1.5″ per terminal and 3″ per battery lug — then add 10% for waste. Each piece is the connector plus at least ½″ onto the insulation at both ends; that overlap is the seal.
Tell it the wire gauge and how many joints. It returns the correct size, the total footage and the exact rolls to order — costed, so you can compare a long roll against short packs before you buy.
Connector plus ~½" onto the insulation each side
Sized from the published AWG chart · rolls rounded up
Shop 3:1 line →Tubing
per piece
by job.
Starting lengths for one piece of tubing. They are working defaults, not standards — measure your own connector and add at least ½″ of overlap onto the insulation at each end.
| Job | Per piece | Why |
|---|---|---|
| Butt splice / inline joint | 2″ (51 mm) | Connector plus ~½" onto the insulation each side |
| Ring or spade terminal | 1.5″ (38 mm) | Barrel plus overlap onto the wire |
| Battery lug / large connector | 3″ (76 mm) | Heavy cable lugs need a longer sleeve |
| Strain relief / bundle wrap | 4″ (102 mm) | Longer runs over a bundle or entry point |
Shrinking it once you have it? Get the heat gun settings.
How the
maths
works.
Total tubing is simply the length of one piece multiplied by the number of pieces, plus a waste allowance. The part people get wrong is the length of one piece: it is not the length of the connector, it is the connector plus the overlap onto the insulation at each end.
That overlap is doing real work. On adhesive-lined dual wall tubing the melted adhesive has to bond to sound insulation either side of the joint — that bond is the waterproof seal. Cut the tubing flush to the connector and you have insulation but no seal, which is the single most common reason a “waterproof” splice wicks moisture down the conductor and fails months later.
Rolls are always rounded up, because you cannot buy two-thirds of a spool. That is why the cheapest option is not always the largest roll: for a handful of joints a 10ft pack often wins on total spend even though it costs more per foot. The comparison above shows both so you can see the crossover for your own job.
Sizes come from the same published AWG chart used by our size calculator and size chart, so all three always agree. We stock 13 sizes from 3/32" to 2" — see the full range.
Length
& quantity
questions.
How much heat shrink tubing do I need per splice?
For a standard butt splice, allow about 2 inches: the length of the connector plus roughly half an inch of overlap onto the wire insulation at each end. Ring and spade terminals need less — around 1.5 inches. Battery lugs and large connectors need 3 inches or more. Always add a waste allowance, since offcuts and mis-cuts are unavoidable on a real job.
How much overlap should heat shrink have on each side?
Aim for at least half an inch (13mm) of tubing sitting on the wire insulation either side of the joint. On adhesive-lined dual wall tubing that overlap is what forms the waterproof seal — the melted adhesive needs undamaged insulation to bond to. Less overlap means the seal can wick moisture along the conductor.
How much extra should I buy for waste?
Ten percent is a sensible default for straightforward work. Increase it to 20 percent if you are cutting many short pieces, working in an awkward position, or if a failed joint would mean pulling the loom apart again. Tubing is cheap relative to the labour of a second trip.
Is it cheaper to buy one long roll or several short packs?
Longer rolls almost always cost less per foot, but only if you use them. For a one-off repair of a handful of joints, a 10ft pack is usually the cheaper total spend even though the per-foot price is higher. The calculator above compares both and shows the lowest total cost for your actual job.
Got your
footage? Order
direct.
- Size Calculator — which tube size fits your wire
- Heat Gun Calculator — gun temperature, distance & nozzle
- How to use heat shrink tubing — the full step-by-step install