Choose hose flow rate, inner diameter, hose length or friction pressure drop. This Darcy–Weisbach model uses a supplied Darcy friction factor and fluid density. Static hose-bib pressure alone does not determine flow.

Use friction pressure drop across a full hose, after accounting for elevation, fittings and nozzle losses.

Optional settings

Default 0.02 is an assumed factor, not a hose rating. Use a value appropriate to the flow and hose; do not enter a Fanning factor.

Default 1,000 approximates water. Use the density at the operating temperature.

Hose Flow Rate Formula

For steady incompressible flow in a full circular hose, the Darcy–Weisbach pressure-loss relationship is Δp = f(L/D)ρv²/2 with Q = πD²v/4. The four solve modes use this relationship with f held constant.

Q = √((Δ p π² D⁵) / (8ρ f L))
  • Q is volumetric flow; the calculator reports L/min and US gallons per minute (US gpm). The SI formula uses m³/s.
  • D is hose inner diameter in meters for the displayed SI formula
  • Δp is friction pressure drop in pascals; ρ is fluid density in kg/m³ and f is the dimensionless Darcy friction factor.
  • L is hose length in meters; Q is m³/s in the displayed SI formula

The calculator converts the selected units to SI. It then solves Δp = 8ρfLQ²/(π²D⁵). Defaults f = 0.02 and density = 1,000 kg/m³ are disclosed assumptions, not measured hose properties. Check f for the resulting Reynolds number and roughness. Fittings, entrance, elevation, nozzle and supply losses are excluded; a Fanning factor must be multiplied by four to obtain a Darcy factor. The old unsupported coefficient/exponent formula has been replaced.

Hose Flow Rate Definition

A hose flow rate is defined as the total volume of water or fluid that moves through a hose per unit of time. This is most often measured in gallons per minute.

Hose Flow Rate Example

How to calculate a hose flow rate?

  1. First, determine the internal diameter.

    Measure the inner diameter of the hose.

  2. Next, determine the length of the hose.

    Measure the total length of the hose.

  3. Next, determine the friction pressure drop.

    Determine the operating friction pressure drop across the hose after accounting for elevation, fittings and nozzle losses.

  4. Finally, calculate the hose flow rate.

    Enter the pressure drop and a suitable Darcy friction factor and fluid density; then calculate using the Darcy–Weisbach model above.

FAQ

What is a hose flow rate?

A hose flow rate is a measure of the amount of water that moves through a hose opening per unit time.

Hose Flow Rate Calculator screenshot