Poiseuille's Law Calculator

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Choose which variable you want to calculate. All others become inputs.
Presets fill in standard viscosity values at approximately 20 C. Override below with Custom.
Resistance of the fluid to flow. Water at 20 C = 0.001002 Pa·s; blood ~0.003 Pa·s.
Pa·s
Inner radius of the tube or pipe. Flow rate scales with the fourth power of radius.
Total length of the tube or pipe segment.
Pressure difference between the inlet and outlet ends of the tube.
Volumetric flow rate through the tube.
Used only for the Reynolds number. Water ~998, blood ~1060, air ~1.2 kg/m3.
kg/m3
Volumetric flow rate (Q)Turbulent (Poiseuille law does NOT apply)
0.000245m3/s

Volume of fluid passing a cross-section per second

Pressure drop (dP)100Pa
Tube radius (r)0.005m
Tube length (L)0.1m
Dynamic viscosity (mu)0.001002Pa·s
Flow resistance (R)408,251.5276Pa·s/m3
Average velocity (v_avg)3.1188m/s
Peak velocity (v_max)6.2375m/s
Reynolds number (Re)31,063.1
Flow regimeTurbulent
31,063.1 Re
Laminar<2300Transitional2300-4000Turbulent4000+

Flow is turbulent at Re = 31063.

  • The volumetric flow rate is 244.9470 mL/s (2.449e-4 m3/s).
  • Hydraulic resistance is 4.083e+5 Pa·s/m3. Like electrical resistance (Ohm's law), higher resistance means less flow for the same pressure.
  • Because flow scales with r^4, halving the radius to 2.500 mm would cut flow to 15309.189 nL/s (1/16th), while doubling the radius to 10.000 mm would increase flow 16-fold to 3919.153 mL/s.

Next stepWarning: Re > 4000 means turbulent flow. Poiseuille's law assumes laminar, steady, Newtonian flow in a long straight tube - the computed values are not valid in turbulent conditions.

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