Hose Clamp Size Guide — How to Measure and Choose the Right Size
Last updated: April 2026
Choosing the wrong hose clamp size is one of the most common installation mistakes — too small and it won't fit, too large and it won't seal properly. This guide explains how to measure correctly, how to read hose clamp sizing, and which sizes suit common applications.
How Hose Clamps Are Sized
Hose clamps are sized by their clamping diameter range, not their band width. A clamp rated 20–32mm can tighten down to 20mm and open up to 32mm. When you select a clamp, you're choosing one whose range comfortably covers the outside diameter of your hose once fitted onto the hose.
Sizes in Australia are measured in millimetres.
How to Measure What Size You Need — 3 Steps
Step 1 — Fit the hose onto the fitting
Slide the hose fully onto its fitting or hose tail before measuring. Rubber hose expands slightly when pushed onto a barb or nipple, and you need the actual installed diameter — not the hose diameter alone.
Step 2 — Measure the outside diameter
Use a tape measure or vernier callipers to measure the outside diameter (OD) of the hose at the point where the clamp will sit. Note the measurement in millimetres.
Step 3 — Choose a clamp range that covers your measurement
Select a clamp whose minimum diameter is a few millimetres below your measurement and whose maximum is a few millimetres above. This gives you adjustment room on both sides. If your measurement falls exactly at the top of one range or the bottom of the next, go with the larger clamp — a clamp that's too small cannot be forced and will damage the thread.
Hose Clamp Size Chart
Common worm drive hose clamp sizes available in Australia:
| Size Range (mm) | Typical Applications |
|---|---|
| 8–16mm | Fuel lines, vacuum hoses, small coolant pipes |
| 12–20mm | Heater hoses, small hydraulic lines |
| 16–27mm | Standard heater hose, fuel filler necks |
| 20–32mm | Common automotive heater and coolant hoses |
| 25–40mm | Radiator hoses (small), irrigation pipe |
| 32–50mm | Standard radiator hose, plumbing, marine |
| 40–60mm | Large radiator hoses, exhaust flex pipe |
| 50–70mm | Industrial hose, truck coolant systems |
| 60–80mm | Large bore automotive and marine hose |
| 70–90mm | Turbo and intercooler hose connections |
| 80–100mm | Large industrial and agricultural hose |
| 90–110mm | Heavy vehicle and mining applications |
| 100–120mm | Large diameter industrial pipework |
| 130–150mm | Very large bore hose connections |
| 150–200mm | Ducting, large agricultural pipe |
| 200–300mm+ | Industrial ducting, large diameter pipe |
For non-standard sizes above 300mm, see our Band Clamp Kits — cut-to-length banding that creates a clamp in any diameter.
Common Sizes by Application
Automotive
- Radiator top/bottom hose: typically 35–55mm OD — choose a 40–60mm clamp
- Heater hose: typically 16–22mm OD — choose a 16–27mm or 20–32mm clamp
- Fuel line: typically 8–12mm OD — choose an 8–16mm or 12–20mm clamp
- Turbo inlet/outlet hose: typically 60–80mm OD — choose a 60–80mm or 70–90mm clamp
Marine
- Freshwater hose (small): 16–25mm — choose 16–27mm or 20–32mm
- Sea cock hose (standard): 32–40mm — choose 32–50mm
- Exhaust hose: 40–75mm depending on engine size
- For saltwater applications, use W4 or W5 grade clamps — see our Marine & Stainless Hose Clamps
Plumbing & Irrigation
- 15mm copper/PVC: OD approximately 18–20mm — choose 16–27mm
- 20mm poly pipe: OD approximately 23–25mm — choose 20–32mm
- 25mm poly pipe: OD approximately 30–32mm — choose 25–40mm
- 32mm poly pipe: OD approximately 38–40mm — choose 32–50mm
Agricultural & Industrial Hydraulic hose connections: typically 20–50mm
Large bore agricultural pipe: 80mm+ — use our Band Clamp Kits for non-standard sizes.
Still Not Sure?
If you've measured and you're still unsure, call us on 1300 027 886 or email sales@uniclamp.com.au — we can help you identify the right size and grade for your application.
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