Bernoulli Equation Calculator
Calculate pressure changes from velocity and elevation differences in fluid flow.
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Bernoulli's equation relates pressure, velocity and elevation in ideal incompressible flow. When fluid speeds up, pressure drops - this is the principle behind airplane wings, carburetors and venturi meters. The equation assumes no friction or viscosity, so real results differ slightly, but it provides excellent first-order estimates for many engineering applications.
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Frequently asked questions
P + 0.5ρv² + ρgh = constant along a streamline. When velocity increases, pressure decreases. For water speeding from 1 to 5 m/s at the same height, pressure drops by 11.976 kPa.
Conservation of energy. Kinetic energy (0.5ρv²) increases, so pressure energy must decrease. Going from 1 to 5 m/s in water, kinetic energy increases by 11,976 Pa, so pressure drops by the same amount.
A venturi narrows the pipe, increasing velocity and dropping pressure. Measuring the pressure difference gives flow rate. A 50 mm to 25 mm reduction at 1 m/s creates a 5.988 kPa pressure drop.
Only for low-speed flows (Mach < 0.3). Above Mach 0.3, compressibility effects matter and you need the compressible Bernoulli equation. For air below 100 m/s at sea level, the incompressible version works well.
Each meter of height difference changes pressure by ρg = 998 × 9.807 = 9787 Pa (9.787 kPa) for water. A 10 m elevation drop adds 97.87 kPa to the pressure.