What does pipe schedule mean?

Pipe schedule is a wall thickness designation. For a given nominal pipe size, a higher schedule usually means a thicker wall and smaller inside diameter.

Is NPS the same as outside diameter?

No. NPS is a nominal pipe size label. For sizes 1/8 through 12, the actual outside diameter is larger than the nominal number; for larger common sizes, the outside diameter often matches the nominal inch size.

How do you calculate pipe inside diameter?

Inside diameter is calculated as outside diameter minus two times the wall thickness. For example, 2 inch Schedule 40 pipe has a 2.375 inch outside diameter and 0.154 inch wall, so the inside diameter is about 2.067 inches.

Pipe size & wall thickness converter

Pipe Schedule Converter

Convert nominal pipe size and schedule into outside diameter, wall thickness, inside diameter, flow area, and approximate steel pipe weight.

Convert NPS and schedule

Choose a nominal pipe size, then pick a schedule available for that size.

Nominal pipe size (NPS) Pipe schedule Rounding

Pipe dimensions 2 in Schedule 40 pipe: OD 2.375 in, wall 0.154 in, ID 2.067 in

Wall thickness changes with schedule; outside diameter is fixed for the NPS size.

Wall thickness 0.154 in / 3.912 mm

Inside diameter 2.067 in / 52.502 mm

Outside diameter2.375 in / 60.325 mm

Flow area3.355 in² / 2,164.5 mm²

Approx. steel weight3.66 lb/ft / 5.44 kg/m

2 inch Schedule 40 pipe has about 2.067 inches of inside diameter after subtracting two walls from the 2.375 inch OD.

Find the nearest listed pipe size

Enter a measured outside diameter to find the closest nominal pipe size in this chart.

Measured OD unit Measured outside diameter

Nearest: NPS 2 Standard OD: 2.375 in / 60.325 mm.

How to use this pipe schedule converter

Select the nominal pipe size, such as 1/2, 2, 4, or 6.
Choose the pipe schedule available for that size.
Read the OD, wall thickness, inside diameter, flow area, and approximate steel pipe weight.

The numbers are useful for layout, rough estimating, fabrication checks, and comparing pipe schedules. For final engineering or purchasing, confirm the specification, material, and tolerance from your supplier.

Common pipe schedule examples

1/2 in Schedule 40 wall ≈ 0.109 in / 2.769 mm
2 in Schedule 40 wall ≈ 0.154 in / 3.912 mm
4 in Schedule 80 wall ≈ 0.337 in / 8.560 mm
6 in Schedule 10 wall ≈ 0.134 in / 3.404 mm

Pipe schedule thickness chart

Common nominal pipe sizes with outside diameter, selected schedules, wall thickness, and inside diameter.

NPS	Schedule	OD	Wall	ID

Pipe schedule FAQ

Does Schedule 80 always have a smaller inside diameter than Schedule 40?

For the same nominal pipe size, yes. The outside diameter stays the same, while Schedule 80 uses a thicker wall, which leaves a smaller inside diameter.

Why is 2 inch pipe not exactly 2 inches outside diameter?

NPS is a nominal label, not a direct outside measurement for smaller pipe sizes. Standard 2 inch NPS pipe has an outside diameter of 2.375 inches.

Can I use the steel pipe weight as an exact shipping weight?

Treat it as an estimate. The weight formula is commonly used for carbon steel pipe, but actual pipe can vary with material grade, manufacturing tolerance, coating, and end finish.