Bernoulli Equation Calculator
Pressure along a streamline — and why faster means lower.
Work out Bernoulli Equation. Pressure along a streamline — and why faster means lower. Names the assumption that breaks it.
Water 1000, seawater 1025, air 1.225, oil about 900.
Assumes an ideal, frictionless fluid. Real pipes lose pressure to viscosity that this does not account for.
Pressure at point 2
170,000 Pa
-30,000 Pa change · flow speeds up
P + ½ρv² + ρgh is constant along a streamline. Where the fluid speeds up the pressure falls, which is counter-intuitive and is exactly how a venturi, a carburettor and an aerofoil work. The equation assumes no viscosity and no losses, so it predicts that a long pipe drops no pressure at all. Real pipes do, and plumbing is sized with Darcy-Weisbach instead. Treat this as the ideal case that real flow falls short of.
How the Bernoulli Equation Calculator works
Enter conditions at two points on a streamline and get the pressure at the second. Where the fluid speeds up the pressure falls, which is the counter-intuitive result behind venturis, carburettors and aerofoil lift.
Also known as: bernoulli principle calculator · venturi calculator · dynamic pressure calculator · fluid pressure velocity calculator
Frequently asked questions
What is Bernoulli's equation?
P + ½ρv² + ρgh stays constant along a streamline in an ideal fluid. Pressure, kinetic energy per unit volume, and potential energy per unit volume trade against each other.
Why does pressure drop where the flow is faster?
Because the total stays fixed. Speeding the fluid up raises the ½ρv² term, so the pressure term must fall to compensate. It is energy conservation, not something specific to fluids.
Does Bernoulli explain how wings work?
Partly, and it is often over-claimed. The pressure difference is real, but the popular 'equal transit time' story is wrong. Lift comes from the wing deflecting air downward, and Bernoulli describes the accompanying pressure field rather than causing it.
When does the equation fail?
Whenever viscosity matters, which is most real pipework. It predicts zero pressure loss along a straight pipe, and real pipes lose plenty. Use Darcy-Weisbach for anything you intend to build.
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