Minor (Local) Head Loss Calculator (h = K·v²/2g) | Online Free Tool | Elysia Tools
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Minor (Local) Head Loss Calculator (h = K·v²/2g)
Compute the minor (local) head loss and pressure drop for pipe fittings, valves and bends: h_m = K·v²/(2g), ΔP_m = K·ρ·v²/2. Ships typical K values for 14 common components (gate/globe/check/angle/ball valves, 90°/45° elbows, tees, sudden contraction/expansion, sharp entrance/exit); choose a preset or supply a custom K. Supports n identical fittings in series. Returns head loss (m, ft) and pressure drop (Pa, kPa, bar). Density in kg/m³, g/cm³ or lb/ft³.
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Key facts
Category
Math & Numbers
Input types
select, number
Output type
json
Sample coverage
4
API ready
Yes
Overview
The Minor (Local) Head Loss Calculator estimates head loss and pressure drop caused by pipe fittings, valves, bends, entrances, exits, sudden contractions, and sudden expansions. Enter a loss coefficient K or choose a preset, then provide flow velocity, fluid density, gravity, and the number of identical fittings in series.
When to use
Estimate local head loss from elbows, valves, tees, and other pipe components.
Calculate the pressure drop caused by one or more identical fittings in series.
Compare fitting options using a preset K value or a custom loss coefficient.
How it works
1Choose a component preset or select Custom K and enter the dimensionless loss coefficient.
2Enter mean pipe velocity, fluid density, gravitational acceleration, and fitting quantity.
3The calculator applies hₘ = n·K·v²/(2g) for head loss and ΔPₘ = n·K·ρ·v²/2 for pressure drop.
4Review head loss in meters and feet, plus pressure drop in pascals, kilopascals, and bar.
Use cases
Pipe system design checks for valves, elbows, tees, and other fittings.
Pump and piping calculations that require local pressure-drop estimates.
Hydraulics coursework and fluid-mechanics examples involving velocity head and K factors.
Examples
1. Estimate loss from four standard elbows
Piping engineer
Background
A piping layout contains four 90° standard elbows. The mean flow velocity is 2 m/s, and the fluid density is 1000 kg/m³.
Problem
Calculate the combined local head loss and pressure drop from the elbows.
How to use
Select 90° standard elbow, enter K = 0.9, velocity = 2 m/s, density = 1000 kg/m³, gravity = 9.81 m/s², and quantity = 4.
The calculator returns a head loss of 0.7339 m, or 2.408 ft, and a pressure drop of 7200 Pa, or 7.2 kPa.
2. Evaluate a fully open globe valve
Mechanical engineer
Background
A water line uses one fully open globe valve with a flow velocity of 1.5 m/s and water density of 1000 kg/m³.
Problem
Determine the valve's local head loss and pressure drop.
How to use
Choose Globe valve (fully open), leave the preset K value in use, enter velocity = 1.5 m/s, density = 1000 kg/m³, gravity = 9.81 m/s², and quantity = 1.
FAQ
What does the loss coefficient K represent?
K is a dimensionless coefficient describing the local resistance of a fitting, valve, bend, or flow transition.
Can I use a preset K value?
Yes. Select a supported component type to use its typical K value. The K field remains editable.
Can I enter my own K value?
Yes. Select Custom K and provide a nonnegative loss coefficient.
How does quantity affect the result?
For n identical fittings in series, the calculator multiplies the single-fitting loss by n.
Which density units are supported?
Density can be entered in kg/m³, g/cm³, or lb/ft³. Results include metric head-loss and pressure-drop units.