Weber Number Calculator

Calculate Weber number to compare fluid inertia with surface-tension forces.

We = ρv²L / σ

Fluid density ρ (kg/m³)

Velocity v (m/s)

Characteristic length L (m)

Surface tension σ (N/m)

Enter valid values in all required fields.

What this formula means

Weber number compares inertial stress with surface-tension stress. Small values favor stable droplets and smooth interfaces; large values indicate that inertia can deform, fragment, or atomize a liquid interface.

Use Weber number for sprays, nozzles, droplets, bubbles, jets, atomization, coating flows, and scale-model similarity. The result should be interpreted with consistent units and with the assumptions of the underlying model in mind.

Worked example

For water at 2 m/s with L = 0.01 m, We ≈ 556, so inertial forces strongly exceed surface tension.

Applications

Use Weber number for sprays, nozzles, droplets, bubbles, jets, atomization, coating flows, and scale-model similarity. It is also useful as an independent check when comparing hand calculations, laboratory measurements, simulations, or preliminary engineering estimates.

Assumptions and common mistakes

Important: Choose the characteristic length that matches the interface phenomenon, such as droplet diameter or jet diameter.

Use SI units unless the field label states otherwise. Keep significant figures appropriate to the accuracy of the inputs, and do not treat a simplified calculator as a replacement for codes, detailed design standards, or professional review.

Frequently asked questions

What equation does this calculator use?We = ρv²L / σ. The calculator evaluates the displayed relationship using the values entered above.

Are the results unit-sensitive?Yes. The input labels use SI units so the displayed output follows the corresponding SI unit.

Can I use this for engineering design?Use it for learning and preliminary checks. Final designs require validated data, applicable standards, safety factors, and professional judgment.