Helixal — Professional Heat Shrink Tubing
Helixal — Professional Heat Shrink Tubing
Enter your wire gauge (AWG), a measured diameter in inches or mm, or the width and height of a rectangular part like a connector body or bus bar. Select the shrink ratio — 2:1, 3:1, or 4:1 — and see every compatible standard heat shrink size with the pre-shrink expanded ID, post-shrink recovered ID, and a best-fit recommendation. No registration, no download. Covers 3/32” to 6” expanded ID.
Not sure how much you need? Work out the length
| Size | Expanded ID | Shrunk ÷3 | Grip |
|---|---|---|---|
| 5/8" | 15.9 mm | 5.3 mm | ✓ grips |
| 3/4" | 19.1 mm | 6.4 mm | ✓ grips |
| 1" | 25.4 mm | 8.5 mm | ✓ grips |
| 1-1/4" | 31.8 mm | 10.6 mm | ✓ grips |
| 1-1/2" | 38.1 mm | 12.7 mm | loose |
| 2" | 50.8 mm | 16.9 mm | loose |
| 2-1/2" | 63.5 mm | 21.2 mm | loose |
| 3" | 76.2 mm | 25.4 mm | loose |
| 4" | 101.6 mm | 33.9 mm | loose |
| 6" | 152.4 mm | 50.8 mm | loose |
Conductor diameters: ASTM B258 (AWG), ASTM B496 (MCM, compact-stranded), IEC 60228 Class 2 (mm²). Insulated OD: NEC Ch.9 Table 5 (THHN) and H07V-K single-core PVC. Crimp barrels and lugs are wider than the wire — size those to the barrel, not the gauge.
Rule: expanded ≥ object × 1.1 · recovered = expanded ÷ 3
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Get the embed code →Core Formula
Recovered ID = Expanded ID ÷ Shrink Ratio
Example (3:1): 6.4 mm ÷ 3 = 2.1 mm recovered ID
Heat shrink tubing is always sized by its expanded (pre-shrink) inner diameter — the diameter before heat is applied. When heated, the tubing shrinks radially by the rated ratio. A 3:1 tube with a 9.5 mm expanded ID will recover to 9.5 ÷ 3 = 3.2 mm inner diameter.
For the tubing to slide over your wire or connector, the expanded ID must be at least 10% larger than the object outer diameter. This is the minimum clearance that allows easy installation without forcing the tubing. For sharp connector edges or irregular profiles, use 15–20% clearance.
For the tubing to grip after shrinking, the recovered ID must be smaller than the object outer diameter. If the recovered ID is larger than or equal to the object OD, the tubing will shrink against the surface but not constrict around it — the fit will be loose. In that case, either switch to a higher ratio (2:1 → 3:1 → 4:1) or size down one increment.
The calculator above applies these rules automatically and marks results as GRIPS (recovered ID < object OD) or LOOSE (recovered ID ≥ object OD) for each compatible size.
Shrink ratio determines how much the tubing contracts in diameter. Higher ratios provide more recovery — which means you can cover a wider range of object sizes and get a tighter grip on smaller diameters.
2:1
Shrinks to 50% of original diameter
Wall Type
Single wall, no adhesive
Best For
Basic electrical insulation, colour coding, abrasion protection on uniform-diameter wire. Best when the wire OD is close to the expanded ID.
Example
1/2" (12.7 mm) tubing → 6.4 mm recovered
3:1
Shrinks to 33% of original diameter
Wall Type
Dual wall with adhesive inner layer (standard for marine/auto)
Best For
Waterproof butt splices, crimp connectors, battery terminal insulation, marine wiring, automotive harnesses. The 3:1 ratio covers wide connector-to-wire transitions in a single piece.
Example
1/2" (12.7 mm) tubing → 4.2 mm recovered
4:1
Shrinks to 25% of original diameter
Wall Type
Single or dual wall depending on manufacturer and spec
Best For
Large connector bodies, MIL-spec cable assemblies, battery lug insulation on large conductors (4/0–500 MCM), cable jacket repair, high-ratio transitions from thick to thin profiles.
Example
1/2" (12.7 mm) tubing → 3.2 mm recovered
Recommended heat shrink tubing size for each AWG wire gauge. The bare conductor diameters are listed for reference, but the recommendation sizes for typical insulated wire of that gauge — which is what you actually sleeve. If you have measured the real outer diameter of your wire or connector, enter it directly in the calculator above instead.
This chart sizes tubing to bare conductor. If you are sealing a crimped butt splice, ring terminal, or lug — which is most repair work — size to the barrel OD instead, because that is the widest point the tube must pass over. Sizing to the wire alone gives you a tube that will not slide over the connector.
Measure the barrel with calipers, allow roughly 20% clearance so the tube slides on cold, then confirm the recovered diameter is smaller than the narrowest thing it must grip. Over a crimp in automotive, marine, or outdoor work, use 3:1 adhesive-lined dual wall — single-wall tubing lets water wick along the strands.
| Wire Gauge | Bare Conductor OD (mm) | Bare Conductor OD (in) | 2:1 Size (insulated wire) | 3:1 Size (insulated wire) |
|---|---|---|---|---|
| 28 AWG | 0.33 mm | 0.013” | 3/32" | 3/32" |
| 26 AWG | 0.41 mm | 0.016” | 3/32" | 3/32" |
| 24 AWG | 0.51 mm | 0.020” | 3/32" | 3/32" |
| 22 AWG | 0.64 mm | 0.025” | 3/32" | 3/32" |
| 20 AWG | 0.81 mm | 0.032” | 1/8" | 3/32" |
| 18 AWG | 1.02 mm | 0.040” | 1/8" | 1/8" |
| 16 AWG | 1.29 mm | 0.051” | 3/16" | 1/8" |
| 14 AWG | 1.63 mm | 0.064” | 3/16" | 3/16" |
| 12 AWG | 2.05 mm | 0.081” | 1/4" | 1/4" |
| 10 AWG | 2.59 mm | 0.102” | 5/16" | 1/4" |
| 8 AWG | 3.26 mm | 0.128” | 3/8" | 5/16" |
| 6 AWG | 4.11 mm | 0.162” | 1/2" | 3/8" |
| 4 AWG | 5.19 mm | 0.204” | 5/8" | 1/2" |
| 2 AWG | 6.54 mm | 0.258” | 3/4" | 5/8" |
| 1 AWG | 7.35 mm | 0.289” | 3/4" | 5/8" |
| 1/0 AWG | 8.25 mm | 0.325” | 1" | 3/4" |
| 2/0 AWG | 9.27 mm | 0.365” | 1" | 3/4" |
| 3/0 AWG | 10.4 mm | 0.410” | 1-1/4" | 1" |
| 4/0 AWG | 11.68 mm | 0.460” | 1-1/4" | 1" |
| 250 MCM | 13.41 mm | 0.528” | 1-1/2" | 1-1/4" |
| 350 MCM | 15.78 mm | 0.621” | 2" | 1-1/2" |
| 500 MCM | 18.9 mm | 0.745” | 2" | 2" |
mm² is a cross-sectional area, not a diameter. 35 mm² cable measures about 12.4 mm across the insulation — sizing tubing as if “35 mm” were the width lands three sizes too big.
| Cable (mm²) | Nearest AWG | Conductor OD (mm) | Insulated OD (mm) | 2:1 Size | 3:1 Size |
|---|---|---|---|---|---|
| 0.5 mm² | 20 AWG | 0.9 | 2.6 | 1/8" | 1/8" |
| 0.75 mm² | 18 AWG | 1.1 | 2.8 | 3/16" | 3/16" |
| 1 mm² | 17 AWG | 1.2 | 3 | 3/16" | 3/16" |
| 1.5 mm² | 16 AWG | 1.5 | 3.4 | 3/16" | 3/16" |
| 2.5 mm² | 14 AWG | 1.9 | 4 | 3/16" | 3/16" |
| 4 mm² | 12 AWG | 2.4 | 4.8 | 1/4" | 1/4" |
| 6 mm² | 10 AWG | 2.9 | 5.6 | 5/16" | 5/16" |
| 10 mm² | 8 AWG | 3.9 | 7.2 | 3/8" | 3/8" |
| 16 mm² | 6 AWG | 4.9 | 8.6 | 1/2" | 1/2" |
| 25 mm² | 4 AWG | 6.2 | 10.8 | 1/2" | 1/2" |
| 35 mm² | 2 AWG | 7.3 | 12.4 | 5/8" | 5/8" |
| 50 mm² | 1/0 AWG | 8.7 | 14.8 | 3/4" | 3/4" |
| 70 mm² | 2/0 AWG | 10.4 | 17 | 1" | 1" |
| 95 mm² | 3/0 AWG | 12.1 | 19.6 | 1" | 1" |
| 120 mm² | 4/0 AWG | 13.6 | 21.6 | 1" | 1" |
| 150 mm² | 300 MCM | 15.2 | 23.8 | 1-1/4" | 1-1/4" |
| 185 mm² | 350 MCM | 16.9 | 26.4 | 1-1/4" | 1-1/4" |
| 240 mm² | 500 MCM | 19.2 | 30 | 1-1/2" | 1-1/2" |
| 300 mm² | 600 MCM | 21.6 | 33.2 | 2" | 2" |
Sources & method
Size heat shrink to the crimp barrel OD — not the wire. Insulated barrel for 22–18 AWG: ~5–6 mm → use 1/4" (6.4 mm) 3:1 dual-wall. For 16–14 AWG barrels (~7–8 mm): use 3/8" (9.5 mm). For 12–10 AWG barrels (~9–11 mm): use 1/2" (12.7 mm). Always use 3:1 adhesive-lined tubing over crimp splices for waterproof marine, automotive, and outdoor work. The adhesive flows past the crimp barrel edges for a hermetic seal.
Recommended ratio: 3:1 Dual WallFor ring lugs and cable end terminals, measure the barrel OD of the lug. A 4 AWG lug barrel is typically 8–9 mm — use 3/4" (19.1 mm) or 1" (25.4 mm) 3:1 to cover the barrel and transition onto the cable insulation. For 2/0 and larger cables with big lug barrels, 4:1 heat shrink covers both the lug body and the smaller cable jacket in a single piece without needing two sizes. ABYC E-11 requires all battery connections to be insulated and protected from accidental short-circuit.
Recommended ratio: 3:1 or 4:1ABYC E-11 Table XI wire sizing applies to all marine electrical work. For below-deck splices, every connection must be waterproof — 3:1 dual-wall adhesive-lined heat shrink is the standard. Use tinned copper wire and 3:1 heat shrink over all butt splices, ring terminal barrels, and inline connections. Size the heat shrink to the crimp barrel or connector body OD, not the wire OD. Allow 12–20 mm of overlap past each connection edge to ensure the adhesive creates a seal beyond the splice point.
Recommended ratio: 3:1 Dual WallFor multi-conductor cable bundles and industrial harnesses, measure the bundle OD after bundling. For strain relief at cable entry points, use 2:1 or 3:1 heat shrink sized to the outer jacket or conduit connector OD. For environmental sealing on panel entry grommets, 3:1 adhesive-lined is preferred — the adhesive fills gaps between jacket and fitting. For large-diameter industrial cables (250–500 MCM), 4:1 tubing in 2"–4" sizes provides reliable insulation on cable splices and lug connections rated for heavy industrial current.
Recommended ratio: 2:1 or 3:1Measure the outer diameter (OD) of the wire, connector, or object you are sleeving. Choose a heat shrink size whose expanded (pre-shrink) inner diameter is at least 10–20% larger than that measurement — so the tubing slides on freely. The recovered (post-shrink) inner diameter must be smaller than the object OD for a tight grip. Formula: Recovered ID = Expanded ID ÷ Shrink Ratio. For 3:1 tubing with a 6.4 mm expanded ID, the recovered ID = 6.4 ÷ 3 = 2.1 mm.
The core formula is: Recovered ID = Expanded ID ÷ Shrink Ratio. For 2:1 tubing, recovered ID = expanded ID ÷ 2. For 3:1 tubing, recovered ID = expanded ID ÷ 3. For 4:1 tubing, recovered ID = expanded ID ÷ 4. To size correctly: (1) measure your object OD, (2) multiply by 1.1–1.2 to get the minimum expanded ID you need, (3) select the smallest available heat shrink size above that minimum, (4) verify the recovered ID is smaller than your object OD for a grip.
2:1 heat shrink shrinks to half its original diameter — used for basic insulation and strain relief where the object diameter is close to the tubing diameter. 3:1 heat shrink shrinks to one-third of its original diameter — the most versatile ratio, standard for connectors, butt splices, and waterproof applications. 3:1 dual-wall adhesive-lined tubing provides a watertight seal. 4:1 heat shrink shrinks to one-quarter of its original diameter — used for large connector bodies, cable repair over non-uniform shapes, and high-ratio transitions where a single tube needs to cover both a thick connector and a thin wire exit.
The standard minimum clearance is 10% — the expanded inner diameter should be at least 10% larger than the object OD so the tubing slides on without forcing. For connectors with sharp edges or uneven profiles, 15–20% clearance is recommended. Too little clearance risks tearing the tubing during installation. Too much clearance (more than 50% oversize on 2:1 tubing) can result in incomplete shrink and loose coverage, especially on very thin wire.
Use 1" (25.4 mm) heat shrink for 50 mm² cable at 2:1, or 3/4" (19.1 mm) at 3:1. Insulated 50 mm² cable measures roughly 16 mm over the jacket, so the 19.1 mm expanded ID slides on and the 3:1 recovery closes it down firmly. Size to the insulated outer diameter, never the conductor cross-section — mm² describes the copper area, not the diameter the tubing has to pass over. For a 50 mm² lug barrel, step up to 1-1/4" (31.8 mm). The metric table above lists every mm² size against its 2:1 and 3:1 recommendation.
You cannot convert directly — mm² is the cross-sectional area of the conductor, while heat shrink is sized by the outer diameter of the insulated cable. Measure the jacket OD with calipers, add 10–20% clearance, then pick the smallest expanded ID above that figure. As a rough guide: 6 mm² ≈ 6 mm OD, 16 mm² ≈ 10 mm, 35 mm² ≈ 14 mm, 50 mm² ≈ 16 mm, 95 mm² ≈ 21 mm. Jacket thickness varies by cable standard, so measure rather than assume. The metric sizing table above gives the 2:1 and 3:1 recommendation for each mm² size.
Both, and they refer to the same tubing. Imperial sizes name the nominal expanded inner diameter in inches — 1/4" tubing has a 6.4 mm expanded ID. Metric sizing states that ID directly in millimetres. Our 2:1 and 3:1 lines are sold on the imperial grid (3/32" to 2"), and the 4:1 line is metric-native (4 mm to 52 mm). When a spec is given in mm², that is conductor area, not diameter — use the metric table above to translate it to a tubing size.
Use 3/8" (9.5 mm) for 2:1 heat shrink on 8 AWG wire, or 5/16" (7.9 mm) for 3:1. Insulated 8 AWG — common in battery and inverter runs — measures roughly 7 mm over the jacket, and the 3:1 recovery closes the smaller 5/16" size down onto it securely. The bare conductor is 3.26 mm (0.128"). For 8 AWG ring terminals and lugs, size to the barrel rather than the cable, since the barrel is the widest point the tube must pass over.
Use 3/4" (19.1 mm) for 2:1 heat shrink on 2 AWG wire, or 5/8" (15.9 mm) for 3:1. Insulated 2 AWG cable measures about 13 mm over the jacket, and 5/8" 3:1 adhesive-lined is the standard seal for 2 AWG battery cable. The bare conductor is 6.54 mm (0.258"). A 2 AWG lug barrel plus palm exceeds 15 mm, so if you are covering the terminal itself step up to 1" (25.4 mm).
Use 1-1/4" (31.8 mm) for 2:1 heat shrink on 4/0 cable, or 1" (25.4 mm) for 3:1. Insulated 4/0 welding and battery cable measures roughly 23 mm over the jacket, which the 25.4 mm expanded ID clears. 3:1 adhesive-lined at 1" is standard for waterproof seals on 4/0 runs. The bare conductor is 11.68 mm (0.460"). For the lug barrel itself, step up to 1-1/2" (38.1 mm).
Size the heat shrink to the crimp barrel OD, not the wire. Insulated butt splice barrels for 22–18 AWG measure 5–6 mm — use 1/4" (6.4 mm) dual-wall 3:1. For 16–14 AWG barrels (7–8 mm) use 3/8" (9.5 mm). For 12–10 AWG barrels (9–11 mm) use 1/2" (12.7 mm). Always use 3:1 adhesive-lined (dual wall) heat shrink over crimp splices in automotive, marine, and outdoor applications to achieve a waterproof seal.
Yes — 3:1 heat shrink can replace 2:1 in virtually all applications where the expanded ID still slides over the object. The higher shrink ratio gives you more recovery, which means the tubing will grip more aggressively and cover a wider range of object sizes. The only case where 2:1 is preferred over 3:1 is when you specifically want a lighter, thinner-walled sleeve for basic insulation on uniform wire, where adhesive sealing is not needed and minimum wall thickness matters.
4:1 heat shrink tubing has the highest shrink ratio and is used for: (1) large connector bodies where the connector barrel is significantly wider than the wire exit, (2) battery lug insulation where the lug OD is much larger than the cable OD, (3) cable repair and re-jacketing over damaged insulation, (4) hose protection where a large bore needs to transition to a smaller connection, and (5) any application requiring a single piece of heat shrink to cover a wide diameter transition. It is common in military, aerospace, and subsea cabling.
Yes — heat shrink tubing shrinks both radially (in diameter, by the rated ratio) and longitudinally (lengthwise, typically 5–10% depending on the material and manufacturer). To account for this, cut your piece 10–15% longer than the area you need to cover, and ensure the tubing overlaps beyond your connection or splice on both ends. For dual-wall adhesive-lined tubing, the overlap also ensures the adhesive flows past the connection edges for a complete environmental seal.
Standard heat shrink tubing ranges from 3/32" (2.4 mm) expanded ID at the small end up to 6", 8", or even larger in specialty rolls. Common stock sizes are 3/32", 1/8", 3/16", 1/4", 5/16", 3/8", 1/2", 5/8", 3/4", 1", 1-1/4", 1-1/2", 2", 3", 4", and 6" expanded ID. Very small sizes below 3/32" exist in specialty electronics packaging. Very large sizes above 6" are used in industrial pipeline and cable insulation. The calculator above covers the full standard industrial range from 2.4 mm to 152 mm expanded ID.
Helixal stocks 2:1 and 3:1 dual-wall heat shrink in 13 sizes — 3/32” to 2”.
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Looking up a specific wire gauge? Every AWG size is answered in the heat shrink size chart & AWG guide. This page covers the sizing method, metric (mm²) cable, and the large-gauge cases.