Hydraulic Gradient Calculator

Calculate hydraulic gradient from head loss and flow-path length for pipes, soils, and groundwater.

i = Δh / L

Head loss Δh (m)

Flow length L (m)

Enter valid values in all required fields.

What this formula means

Hydraulic gradient is the change in total hydraulic head per unit distance in the direction of flow. It is dimensionless and acts as the driving slope in Darcy flow through porous media and in many pipe-flow interpretations.

Use hydraulic gradient in groundwater studies, seepage, filters, earth dams, soil permeability tests, and pipeline energy-grade lines. The result should be interpreted with consistent units and with the assumptions of the underlying model in mind.

Worked example

A 2 m head loss over 50 m gives i = 2/50 = 0.04, equivalent to 4 m of head loss per 100 m.

Applications

Use hydraulic gradient in groundwater studies, seepage, filters, earth dams, soil permeability tests, and pipeline energy-grade lines. It is also useful as an independent check when comparing hand calculations, laboratory measurements, simulations, or preliminary engineering estimates.

Assumptions and common mistakes

Important: Use total head difference along the actual flow length. Mixing elevation difference alone with total head can give the wrong driving gradient.

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?i = Δh / L. 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.