Use calipers, tape measures, or special tools to measure the outer diameter (OD), inner diameter (ID), and other required data of the pipe.
How to Measure a Pipe Size？
The fastest way to measure a pipe size is to measure its outside diameter (OD) with a caliper and compare it with a standard NPS pipe size chart.
If you cannot access the outside diameter directly, measure the pipe circumference with a tape and calculate:
Outside Diameter = Circumference ÷ 3.1416
For accurate identification, always verify:
• Outside Diameter (OD)
• Wall Thickness
• Inside Diameter (ID)
• Nominal Pipe Size (NPS)
• Pipe Schedule
How to Measure a Pipe Size？
Outer diameter measurement
1. Place the measuring tool close to the outer wall of the pipe, and circle it horizontally along the axis of the pipe, and record the maximum value.
2. Wrap the thin rope around the outer wall of the pipe, unroll it, and use a tape measure to measure the length of the thin rope, and then calculate the outer diameter using the formula diameter = circumference/π (3.14).
Inner diameter measurement
1. Insert the caliper probe into the pipe, adjust it to contact the inner wall on both sides, and read the number directly
2. Apply coupling agent to the outer wall of the pipe, and the instrument will emit ultrasonic waves that penetrate the pipe wall and reflect, automatically calculating the inner diameter
Fomula:
Outside Diameter = Circumference ÷ π
Inside Diameter = OD − (2 × Wall Thickness)
Which Pipe Dimension Should You Measure?
Which dimension depends on your purpose.
For purchasing→ Measure OD
For replacing an existing pipe→ Measure OD + Wall Thickness
For flow calculation→ Measure ID
For welding→ Measure OD + Bevel
For fittings→ Measure Nominal Pipe Size (NPS)
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