General-service tubing
ASTM A269/A269M covers nominal-wall stainless tubing for general corrosion-resisting and temperature service.
Technical guide
Stainless Steel Tube Size Chart
Specify tube by outside diameter, wall thickness, shape, standard, grade and condition. Do not substitute pipe NPS and schedule language unless the product is actually ordered as pipe.
Tube basisOD × wall thickness
Calculated valueID = OD - 2 × wall
Order controlsStandard, grade, finish and tolerance
Decision summary
Distinguish tube dimensions from pipe designations
Tube is commonly ordered by actual outside dimensions and wall, while stainless pipe uses nominal pipe size and schedule tables. The terms are not interchangeable.
Mechanical tubing
ASTM A554 covers welded mechanical tubing in round, square, rectangular and special shapes.
Pipe systems
ASME B36.19 standardizes dimensions for welded and seamless wrought stainless pipe.
Reference table
Common round-tube dimension examples
The table calculates inside diameter from nominal OD and wall. It is a planning reference, not an inventory or tolerance claim.
| Outside diameter | Wall thickness | Calculated inside diameter | Example specification text |
|---|---|---|---|
| 6.35 mm (0.250 in) | 0.89 mm (0.035 in) | 4.57 mm (0.180 in) | 6.35 mm OD × 0.89 mm wall |
| 9.53 mm (0.375 in) | 0.89 mm (0.035 in) | 7.75 mm (0.305 in) | 9.53 mm OD × 0.89 mm wall |
| 12.70 mm (0.500 in) | 1.24 mm (0.049 in) | 10.22 mm (0.402 in) | 12.70 mm OD × 1.24 mm wall |
| 19.05 mm (0.750 in) | 1.65 mm (0.065 in) | 15.75 mm (0.620 in) | 19.05 mm OD × 1.65 mm wall |
| 25.40 mm (1.000 in) | 1.65 mm (0.065 in) | 22.10 mm (0.870 in) | 25.40 mm OD × 1.65 mm wall |
| 38.10 mm (1.500 in) | 2.11 mm (0.083 in) | 33.88 mm (1.334 in) | 38.10 mm OD × 2.11 mm wall |
| 50.80 mm (2.000 in) | 2.77 mm (0.109 in) | 45.26 mm (1.782 in) | 50.80 mm OD × 2.77 mm wall |
Calculated ID assumes concentric nominal dimensions. Actual ID varies with OD and wall tolerances and manufacturing condition.
Need a tube size suppliers can verify?
Send actual OD, wall, length, standard, grade, process, finish, tolerance and testing requirements.
Working method
Write the tube requirement in a consistent order
A complete dimensional line lets the supplier check standard coverage, tooling, tolerance, test and availability without guessing what “one-inch tube” means.
Name the product and standard
State tube versus pipe, governing ASTM/ASME/EN specification and required edition.
State shape and dimensions
For round tube use OD × wall × length. For square or rectangular tube state outside dimensions, wall and corner requirements.
Add material and condition
Include grade/UNS, welded or seamless, heat treatment, finish and any cold-work condition.
Define tests and documents
State hydrostatic or nondestructive test, dimensional inspection, surface acceptance, MTC and third-party needs.
Limits and escalation
Dimensions alone do not establish suitability
Pressure design
Use the governing piping or pressure code, allowable stress, joint efficiency and design conditions.
Sanitary service
Specify the sanitary tubing standard, internal finish, weld condition and cleaning/validation needs.
Structural use
Confirm the structural product standard and final-section properties instead of assuming mechanical tubing is structurally qualified.
Bending and forming
Centerline radius, ovality, thinning, seam orientation and final gauge requirements must be agreed.
Visual process context
Show the dimensional and inspection context behind the tube callout.
Use one image for the physical tube form and another for measurement or inspection evidence.
Interactive planning aid
Calculate nominal inside diameter from OD and wall
Enter both values in millimetres. The result is geometric only and excludes manufacturing tolerances.
Frequently asked questions
Stainless steel tube size FAQ
No. Tube is commonly specified by actual outside diameter, while nominal pipe size is a designation tied to standardized pipe outside diameters and schedules.
For a simple nominal calculation, subtract twice the wall thickness from the outside diameter. Actual ID varies with permitted OD and wall tolerances.
ASTM A269 covers product requirements and gives a usual minimum range, but manufacturers can supply agreed sizes. A purchase order must state the exact dimensions and supplementary requirements.
Do not assume so. Confirm the structural design standard and mandatory final-section properties. Current ASTM work has specifically addressed structural tubing requirements.
Method, sources and review
Traceable sources and review status
Official specification scope for seamless and welded austenitic stainless tubing for general service.
Official specification scope and size range for welded stainless mechanical tubing.
Official pipe-dimension standard used to distinguish pipe NPS/schedule from tube OD/wall ordering.
Official definition that one international inch equals exactly 25.4 millimetres.
Use the contract-specified current standard edition and manufacturer-certified dimensions. The examples and calculator are nominal planning aids, not tolerance or availability declarations.
Tube dimensions context
Read the outside diameter, wall and delivery condition together.
A tube size chart is only useful when the specified diameter, wall thickness, standard, straightness, finish and inspection basis all match the requirement.
- Outside diameter
- Wall thickness
- Delivery condition