Bend radius calculator Hose length, to the millimetre.
Set the angle, the bend radius and the two legs, and get the length of hose you need — with the part drawn to your figures.
Calculate
Drag a dimension — the part redraws and the length updates.
Drag to rotate
Part dimensions
How it’s worked out
The arc is simple. The straight runs are where lengths go wrong.
The minimum bend radius is the tightest curve a hose takes without kinking or shortening its life. Bend it tighter than it is designed for and the wall collapses, the flow drops and the hose fails early — which is why the radius has to be settled before the length is ordered, not after.
L = A360° × 2πr
- L
- Length of the bent section
- A
- Bend angle, in degrees
- r
- Bend radius, to the hose centreline
45°
90°
135°
The correction
The arc does not start r from the vertex — it starts r · tan(A/2) from it. The two only match at 90°. At 135° the arc begins 2.4 times further along each leg, and a leg shorter than that cannot be made.
Worked example
90°, legs of 400 and 600 mm, r = 334 mm
- Bent section 90/360 × 2π × 334 525 mm
- Straight A 400 − 334 66 mm
- Straight B 600 − 334 266 mm
- Hose required 857 mm
Figures from Venair’s technical guide · Read the full guide
Measuring each dimension
Inside the bore, from the vertex, to the centreline.
Diameters
- Inner Ø
- The one that fits over the metal pipe. Measure inside the bore, on a straight run — never around the outside.
- Outer Ø
- Only vacuum hose carries both figures: measure the outer wall with a calliper.
- Inlet Ø
- The wide end. Measured inside, on the straight section.
- Outlet Ø
- The narrow end, also measured inside.
Lengths
- Length
- Overall length of the part along its axis.
- Leg A
- From where the two axes cross to the end of the leg — not from where the curve stops.
- Leg B
- The other straight run, measured the same way: from the vertex.
The bend
- Angle
- The turn between the two legs. Catalogue: 45°, 90° and 135°.
- Bend radius
- Measured to the centreline of the hose, which is the method in Venair’s guide. The minimum each hose takes is on its data sheet — bend it tighter and it kinks.
Questions
Five questions before you order.
01 What is the minimum bend radius of a hose?
The tightest curve a hose takes without kinking or shortening its life. Bend it tighter and the wall collapses, the flow drops and the hose fails early. It depends on the wall, the reinforcement and the bore, so each hose lists its own on its data sheet.
02 How do you calculate the length of a bent hose?
Work out the arc with L = A/360° × 2πr, then add the two straight runs. Each straight run is the leg — measured from where the two axes cross — minus r · tan(A/2). At 90° that correction is simply r.
03 Centreline radius or inside radius: which should I use?
Centreline. Inside radius measures to the innermost surface of the bent hose; centreline radius measures to its middle, and it is the one that gives the true length for any configuration. It is the method in Venair’s guide and the one this calculator uses.
04 Why isn’t the straight run just the leg minus the radius?
Because that only holds at 90°. The arc meets each leg r · tan(A/2) from the vertex: 0.41 r at 45°, r at 90° and 2.41 r at 135°. Ignore it and a 45° elbow comes out short and a 135° one comes out long.
05 Where do I find the minimum bend radius of a specific hose?
On its data sheet. Wall, reinforcement and bore all change it, so no single rule covers the whole range: this tool does the geometry, the limit comes from the part.