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Hydraulic Hose Sizing Calculator

Work out hydraulic hose sizing instantly with clear inputs, formula shown and shareable results.

About Hydraulic Hose Sizing Calculator

Hydraulic hose is sized by fluid velocity, and the limit differs by duty: about 20 ft/s in pressure lines, 10 ft/s in returns and only 4 ft/s in suction lines where cavitation is the risk. Area in square inches is flow in GPM times 0.3208 divided by velocity in feet per second.

Formulas

Flow area

A in² = GPM x 0.3208 / velocity ft/s

Bore

ID in = sqrt(4A / pi)

Worked example

With the default values below, Hydraulic Hose Sizing Calculator returns Hose bore required of 0.452. Change any input above and every figure here is recalculated in your browser.

Inputs used

Flow rateminimum 0.1 GPM
10 GPM
Line typeone of Pressure line — 20 ft/s, Return line — 10 ft/s, Suction line — 4 ft/s
Pressure line — 20 ft/s

Results

Hose bore required
0.452 in
Nearest dash size
-8 (1/2 in)
Flow area required
0.1604 in²
Design velocity used
20.0 ft/s

Step by step

  1. 1Values used
  2. 2Flow area
  3. 3Bore
  4. 4Hose bore required= 0.452 in
  5. 5Nearest dash size= -8 (1/2 in)
  6. 6Flow area required= 0.1604 in²
  7. 7Design velocity used= 20.0 ft/s

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Hydraulic Hose Sizing figure worked out?

A in² = GPM x 0.3208 / velocity ft/s. Hydraulic hose is sized by fluid velocity, and the limit differs by duty: about 20 ft/s in pressure lines, 10 ft/s in returns and only 4 ft/s in suction lines where cavitation is the risk.

Why must suction lines be so much larger?

Pressure at the pump inlet is already below atmospheric. Any additional velocity head can drop it below the oil's vapour pressure, causing cavitation that destroys the pump.

What values do I need to enter?

This calculator takes 2 inputs: Flow rate, Line type. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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