Pressure Drop Calculator

System pressure drop from pipe, fittings, and filters.

Inputs

Air flow (CFM free air)

Pipe inside diameter (in)

Total equivalent length (ft)

Supply pressure (psig)

Number of filters

Number of dryers

Tab to move between fields

Results

Total pressure drop (psi)

15.45

Delivered pressure (psig)

84.5

Pipe friction drop (psi)6.45

Component drop (psi)9

Drop as % of supply15.5

Pipe velocity (ft/s)9.2

Energy penalty (%)7.7

How to Use This Calculator

Enter the pipe inside diameter in inches and pipe length in feet.
Set the volumetric flow rate in CFM and system pressure in PSI.
Input air temperature and pipe roughness factor for your pipe material.
Review the calculated pressure drop in PSI.
If drop exceeds 10% of working pressure, increase pipe diameter or reduce run length.

How the result changes with Pipe inside diameter (in)

Pipe inside diameter (in)	Total pressure drop (psi)	Delivered pressure (psig)
1.47	42.48	57.5
4.39	9.18	90.8
7.9	9.01	91
11	9	91

What each input means

Air flow (CFM free air): Flow rate in cubic feet per minute at atmospheric pressure.
Pipe inside diameter (in): Inside diameter of the main pipe run. 2.067 in = 2" NPS Schedule 40.
Total equivalent length (ft): Total equivalent pipe length including straight runs and fittings equivalent lengths.
Supply pressure (psig): Compressor discharge or header pressure.
Number of filters: Total inline filters (coalescing, particulate, carbon). Each adds ~2.5 psi drop.
Number of dryers: Inline air dryers. Refrigerated dryer adds ~4 psi, desiccant ~6 psi.

What each result means

Total pressure drop (psi): Combined pressure drop from piping and all components.
Delivered pressure (psig): Pressure available at the point of use.
Pipe friction drop (psi): Pressure drop from pipe friction alone (Darcy-Weisbach).
Component drop (psi): Pressure drop from filters, dryers, and other inline equipment.
Drop as % of supply: Total pressure drop as percentage of supply pressure. Best practice: < 10%.
Pipe velocity (ft/s): Air velocity in the pipe at operating pressure.
Energy penalty (%): Estimated extra compressor energy due to pressure drop (rule: ~1% per 2 psi).

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Air flow (CFM free air) = 100, Pipe inside diameter (in) = 2.067, Total equivalent length (ft) = 200, Supply pressure (psig) = 100 = 6 input(s) provided
Calculate Total pressure drop
Total pressure drop = pipeDp + filterDp + dryerDp
15.45 = 15.45
Calculate Delivered pressure
Delivered pressure = systemPressurePsig - totalPressureDrop
84.5 = 84.5
Calculate Pipe friction drop
Pipe friction drop = frictionFactor * (pipeLengthFt / hydraulicDiameter) *
6.45 = 6.45
Calculate Component drop
Component drop = round((filterDp + dryerDp) * 100) / 100
9 = 9

Engine last updated July 28, 2026. Checked against 1 independently-derived test — how we verify calculators.

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