State OD, Wall Thickness and Length Separately
For example: OD 3/8 in × WT 0.028 in × L 20 ft, or OD 9.525 × WT 0.711 × L 6096 mm. Keep the requested tolerance with the original unit system.
Buyer Tool
Imperial / Metric Converter for Tube Dimensions and Engineering Units
Convert inches to millimetres, feet to metres, pounds to kilograms, psi to bar and other common units used in tube drawings, RFQs and industrial equipment specifications.
Engineering Unit Converter
Select a unit group, enter a value, and choose the source and target units. Decimal and fractional inch inputs are accepted.
Examples: 0.375, 3/8 or 1 1/2
To
The result updates automatically as you type.
0.375 in × 25.4 = 9.525 mm
Quick tube-size reference
Common Fractional Inch Sizes in Millimetres
Click a value to load it into the converter. These direct dimension conversions are useful when reviewing tube OD, wall thickness and cut length.
For drawings and RFQs
How to Use Converted Values in a Tube Inquiry
A correct unit conversion helps communication, but the original drawing units and tolerances should remain visible during technical review.
Do Not Round Critical Dimensions Too Early
Use sufficient decimal places when converting thin wall thicknesses, precision tube sizes, groove geometry or pressure values. Final acceptance should follow the drawing or purchase specification.
Nominal Pipe Size Is Not a Direct OD Conversion
NPS and DN are nominal designations. Their actual outside diameter and wall thickness depend on the applicable pipe standard and schedule, so they should not be converted as ordinary length values.
| Conversion | Exact or standard factor used | Typical tube-procurement use |
|---|---|---|
| Inch to millimetre | 1 in = 25.4 mm exactly | OD, wall thickness, tolerances and drawing dimensions |
| Foot to metre | 1 ft = 0.3048 m exactly | Straight tube length, coil length and total order length |
| Pound to kilogram | 1 lb = 0.45359237 kg exactly | Order weight, packing weight and logistics preparation |
| psi to bar | 1 psi ≈ 0.0689476 bar | Operating pressure, design pressure and test pressure review |
| US gpm to L/min | 1 US gpm = 3.785411784 L/min | Cooling-water and process-flow discussion |
FAQ
Imperial and Metric Conversion Questions
How many millimetres are in one inch?
One inch equals exactly 25.4 millimetres. To convert an inch value to millimetres, multiply it by 25.4. For example, 3/8 in equals 9.525 mm.
Can I enter fractional inch tube sizes?
Yes. The converter accepts decimals, simple fractions such as 3/8, and mixed fractions such as 1 1/2. Select Length, choose inches as the source unit, and millimetres as the target unit.
Should a converted tube dimension be rounded?
Rounding depends on the purpose and applicable tolerance. For quotation and technical review, keep enough decimal places to avoid changing the intended dimension. The original drawing or specification remains the controlling document.
Is DN the metric equivalent of NPS?
DN and NPS are related nominal pipe designations, not direct measurements. Actual pipe OD and wall thickness must be checked against the relevant standard and schedule. Tube OD should be stated as an actual dimension.
Can this converter calculate tube weight?
This page converts units only. For theoretical tube, sheet or plate weight, use the GAOFA TECH Product Weight Calculator and confirm the selected material density and dimensions.
Ready to Prepare a Tube Inquiry?
After converting the units, send the material grade, OD, wall thickness, length, quantity, standard or drawing, and any special tolerance or inspection requirements.
Conversion results are provided for convenient specification review. Verify critical design, pressure, temperature and dimensional values against the applicable engineering standard, drawing and customer specification.