Differential Pressure Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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Fluid calculations are especially sensitive to density, viscosity, geometry, pressure conventions, and unit systems. Differential Pressure Calculator narrows that problem to the relationship used on this page, making the displayed differential pressure easier to audit against the inputs and the governing equation.

What this calculator does

The Differential Pressure Calculator uses Specific gravity, Discharge or volumetric flow rate, Flow factor to estimate the page’s Differential pressure from the fluid-mechanics relationship below. It is meant for a defined geometry and property set, so the useful part is not just the headline number but also whether your density, viscosity, dimensions, pressure reference, and flow convention match the model.

How to use it

Start with the fields that actually drive this result: Specific gravity, Discharge or volumetric flow rate, Flow factor. Keep units consistent with the menus beside the fields and avoid mixing values measured under different conditions. After calculating, change one input at a time if you are comparing scenarios; that makes cause-and-effect much easier to see.

How the calculation works

The page uses the simplified flow-coefficient relation Δp = SG·(Q/K)². Because Q and K can be defined in different unit conventions by different industries, their units must match the convention used for the entered coefficient.

Example

Using the page’s default example (Specific gravity = 1; Discharge or volumetric flow rate = 1 m³/s; Flow factor = 1), the calculator reports Differential pressure of 1 Pa. Change one driving input at a time and confirm the result moves in the direction predicted by the equation; that is a quick way to catch a unit or mode mistake.

How to interpret the result

Interpret the Differential pressure within the fluid, geometry, pressure reference, and property values you entered. A numerically plausible answer can still be physically wrong if gauge/absolute pressure, diameter/radius, viscosity type, or unit convention is mismatched, so compare the result with the assumptions as well as the formula.

Limitations and notes

This is a coefficient-based shortcut, and the units of Q and K are inseparable from the coefficient convention. It should not be treated as a universal SI equation unless the coefficient has been defined for those units.