Pipe Flow Calculator
Free online Pipe Flow Calculator that runs directly in your browser.
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Other tools you may find usefulPipe Flow Calculator - Accurate Q Calculations for Various Methods and Media
This tool determines the flow rate in pressure lines based on pressure drop or equivalent head loss. It supports the Darcy–Weisbach and Hazen–Williams methods, calculates the Reynolds number, flow speed and converts the result to m³/s, m³/h, L/s, L/min, GPM US and GPM UK. The interface uses labels known from the Blade template, such asPressure drop Δp (dp_value, dp_unit),Height loss hf (dh_value),Inner diameter D (D_value, D_unit),Pipeline length L (L),Sum of local losses KΣ (Ksum),Density ρ (rho),Dynamic viscosity μ (mu),Roughness ε (eps_preset, eps_value) and coefficientHazen–Williams C (C).
You chooseCalculation method (method) and you work in two scenarios: a given pressure dropΔpor a given height losshf. The calculator uses the internal diameter of the pipeD, the length of the sectionL, the absolute roughnessεand the sum of the local loss coefficientsKΣ. The result isQ, v i Re, as well as a set of unit conversions.
Formulas and theory
1. Basics of flow energy
The Darcy–Weisbach equation relates the linear losses to the friction coefficientfand the Reynolds number:
h_f = f · (L/D) · (v² / 2g)
The pressure drop associated with this loss is described by the relationship:
Δp = ρ · g · h_f
We model local losses by the total coefficientKΣ:
h_m = K_Σ · (v² / 2g)
Total energy loss:h = h_f + h_m. This allows you to associateQ, vand known installation parameters.
2. Speed and intensity
Speedvand intensityQare connected by a simple circular cross-section geometry:
A = π · D² / 4v = Q / A
In computational practice we findv i Qby solving system with losses, and then we calculateRe:
Re = (ρ · v · D) / μ
3. Friction coefficient f
Laminar(Re < 2300):
f = 64 / Re
Turbulent(Re ≥ 2300): recommended explicit or iterative approximations:
Colebrook–White(iterative):
1/√f = −2 · log10( (ε/(3.7D)) + (2.51/(Re √f)) )
Swamee–Jain(explicit, fast):
f = 0.25 / [ log10( (ε/(3.7D)) + (5.74 / Re^0.9) ) ]^2
Calculator useseps_presetor eigenvalueeps_valueto evaluate the roughness and selectf.
4. Hazen–Williams for water
For water in the range of typical temperatures, the Hazen–Williams empirical formula is used, useful for quick estimates:
Q = 0.278 · C · D^2.63 · S^0.54
whereS = h / Lis the hydraulic drop,Cis the material roughness coefficient pipes, andDin meters. The method does not require ρ or μ, but is limited to wate