To calculate the pipe length, the method you use depends on what information you already have and what type of pipe layout you're dealing with. Here are the common scenarios:
1. Based on Flow and Velocity (for fluid flow design)
If you're designing for fluid flow and want to calculate the required pipe length:
Not typically calculated directly — length is usually measured or designed based on system layout (building/plant).
However, if you have total pressure loss and need to estimate pipe length:
Use the Darcy-Weisbach equation to relate pressure loss to pipe length.
L=ΔP⋅D/f⋅ρ⋅v2/2
Where:
L = pipe length (m)
ΔP = pressure drop (Pa)
D = pipe diameter (m)
f = friction factor (dimensionless)
ρ = fluid density (kg/m³)
v = fluid velocity (m/s)
2. For Coiled Pipe / Rolled Pipe
If the pipe is wound in a coil, and you want to estimate the length from dimensions:
L=N⋅π⋅(Douter+Dinner)/2L
Where:
N = number of turns
Douter, Dinner = outer and inner diameters of the coil
3. From Pipe Weight (If You Have Weight and Want Length)
You can calculate pipe length from its total weight:
Length=Weight/Weight per meter
To calculate weight per meter for a steel pipe:
Weight/m=0.02466×(D−t)×t
Where:
D = outer diameter (mm)
t = wall thickness (mm)
4. Using CAD / P&ID / Isometric Drawing
If you are working on a project:
Pipe lengths are taken directly from CAD drawings or isometric piping layouts.
Add straight sections + fittings + allowances.
5. Quick Manual Measurement (In Field)
Use:
A measuring tape for straight pipe.
A measuring wheel or string for curved sections.
Add standard lengths for elbows, bends, and fittings (usually in piping tables).
