GI Pipe Size and Weight Chart: Dimensions in mm and kg/m

Common GI pipe sizes range from DN15 (½ inch) to DN150 (6 inches). Their actual outside diameters are larger than their nominal inch sizes. A DN50 medium pipe, for example, has a specified outside diameter of 60.3 mm, a 3.6 mm wall and a plain-end weight of approximately 5.03 kg/m.

The tables below cover common medium and heavy GI pipes associated with EN 10255 and the former BS 1387. Buyers comparing galvanized steel pipes should still confirm the required standard, wall series, pipe end and length before ordering.

GI remains a common trade term for galvanized iron pipe, although most modern GI pipes are welded carbon steel tubes protected by a zinc coating.

GI Pipe Size Chart: DN, OD and Thread Size

A GI pipe size is nominal. It identifies the pipe and its compatible fittings, but it does not state the exact outside diameter.

For example, a 2-inch pipe is designated DN50 but has a specified outside diameter of 60.3 mm. The outside diameter remains the same for medium and heavy pipes; their wall thicknesses and internal diameters differ.

Use the specified OD when calculating theoretical weight. Use the permitted OD range when checking pipe dimensions or compatibility with fittings, threads and grooved connections.

GI Pipe Weight Chart for Medium and Heavy Series

The following GI pipe weight chart gives plain-end theoretical weights in kilograms per metre and kilograms per 6-metre pipe. Threaded and socketed pipes are slightly heavier because the socket adds material.

Medium GI Pipe Weight Chart

Heavy GI Pipe Weight Chart

These figures are reference values rather than guaranteed shipping weights. Manufacturing tolerances, zinc coating, end preparation and actual pipe length can change the final result.

How Do GI Pipe Sizes in mm Relate to GI Pipe Sizes in Inches?

GI pipe sizes in mm normally use DN or nominal bore. GI pipe sizes in inches use the corresponding nominal thread size. Both identify the same size category; neither is a direct measurement of the outside diameter.

The most common conversions are:

This distinction matters when replacing existing pipe. Measuring an outside diameter of about 60 mm does not indicate a 60 mm nominal pipe. It normally identifies a DN50 or 2-inch pipe.

What Are GI Pipe Class B and GI Pipe Class C?

GI pipe Class B and Class C are common purchasing terms in South Asia, the Middle East and some African markets. They are particularly associated with IS 1239 and similar class-based specifications.

Class B generally refers to a medium-wall pipe. Class C refers to a heavier-wall pipe. However, these terms should not be used without naming the governing standard. The same trade description may be interpreted differently by suppliers in different markets.

For projects using European specifications, EN 10255 and BS 1387 welded steel pipe should be ordered by Medium or Heavy series rather than relying only on Class B or Class C terminology.

Class B GI Pipe Thickness

Class B GI pipe thickness increases with nominal diameter. In the medium-series table above, it ranges from 2.6 mm for DN15 and DN20 to 5.0 mm for DN125 and DN150.

A quotation that states only “Class B GI pipe” remains incomplete. It should also include:

• Applicable standard
• Nominal size
• Required wall thickness
• Pipe length
• Zinc coating method
• Plain, threaded, grooved or socketed ends

GI Pipe Class C

GI pipe Class C normally describes the heaviest of the A, B and C classes. Its thicker wall produces a higher weight per metre and a smaller internal diameter than a Class B pipe of the same nominal size.

The heavier wall may provide greater mechanical strength, but Class C should not be selected from weight alone. Design pressure, joint type, corrosion allowance, fluid, temperature and applicable project code must also be considered.

Class C is also not automatically equivalent to Schedule 80. The two designations come from different sizing systems and should be compared using actual OD and wall thickness.

How Do You Calculate GI Pipe Weight per Meter?

GI pipe weight per meter can be estimated from the outside diameter and wall thickness.

Weight formula:

Weight (kg/m) = 0.02466 × t × (OD − t)

Where:

• OD = outside diameter in mm
• t = wall thickness in mm
• 0.02466 = constant based on a steel density of approximately 7,850 kg/m³

For example, a DN50 medium GI pipe has an outside diameter of 60.3 mm and a wall thickness of 3.6 mm.

Weight per meter:

0.02466 × 3.6 × (60.3 − 3.6) = 5.03 kg/m

To calculate the weight of a 6-metre pipe:

Weight per pipe = Weight per meter × Pipe length

5.03 × 6 = 30.18 kg

The estimated weight of one 6-metre DN50 medium GI pipe is therefore 30.18 kg.

This formula calculates the theoretical weight of the steel pipe body. It does not include the additional weight of the zinc coating, sockets, couplings or packaging.

Why Can Actual GI Pipe Weight Differ From the Chart?

A measured pipe may not match the chart exactly. Several factors affect its final weight.

First, pipe standards permit dimensional tolerances. Small variations in outside diameter and wall thickness are multiplied across the full pipe length.

Second, galvanizing adds zinc to the internal and external surfaces. A heavier coating increases total mass, although the difference is usually much smaller than the effect of changing the wall series.

Third, the end condition matters. A threaded and socketed pipe weighs more than a plain-end pipe. Grooving does not change the basic size designation but may slightly affect the final weight.

Finally, cutting tolerance affects each piece. A pipe ordered at 6 metres will not have the same weight as one supplied at 5.8 metres or 6.4 metres.

Use standard weights for preliminary calculations. Use the supplier’s packing list or verified bundle weight for freight planning and final delivery records.

How Should GI Pipe Sizes Be Specified When Ordering?

A complete order description removes ambiguity between standards and markets. It should combine the pipe standard, nominal size, series, coating, end condition and length.

For example:

EN 10255 Medium, DN50, 3.6 mm wall, hot-dip galvanized, 6 m length, BSPT threaded ends with sockets.

For a purchasing inquiry, include:

1. Standard and material grade
2. DN or inch size
3. Medium, Heavy or specified wall thickness
4. Hot-dip or pre-galvanized finish
5. Zinc coating requirement
6. Plain, beveled, threaded or grooved ends
7. Pipe length and quantity
8. Inspection and certification requirements

This information allows the manufacturer to confirm dimensional compatibility, production availability and estimated shipment weight.

Conclusion

GI pipe weight depends on its DN, outside diameter, wall thickness and length. Medium and heavy pipes of the same nominal size therefore have different weights.

Class B, Class C and Schedule designations are not interchangeable. For ASTM-based products, refer to the galvanized steel pipe dimensions chart.

Confirm Your GI Pipe Specifications

Send Baolai your required standard, size, wall thickness, length and quantity through the contact page. We can confirm available specifications and estimate the order weight.

Frequently Asked Questions

Does galvanizing increase GI pipe weight?

Yes. The zinc coating adds some weight depending on the pipe size and coating thickness. Use the actual packing weight for final freight calculations.

Does the chart include threaded ends and sockets?

No. The tables show plain-end pipe weights. Threads, sockets and couplings may increase the finished weight.

How do I calculate the weight of a different pipe length?

Multiply the weight per metre by the required length. A pipe weighing 5.03 kg/m will weigh about 29.17 kg at 5.8 metres and 30.18 kg at 6 metres.

Is Class B GI pipe the same as Schedule 40?

No. They belong to different sizing systems. Compare the applicable standard, outside diameter and wall thickness before substituting one for the other.

Should freight use theoretical or actual pipe weight?

Use theoretical weight for early planning. Final freight documents should use the verified bundle or packing-list weight, which includes coatings, ends and packaging.

External Sources

• BSI: BS EN 10255 Non-alloy steel tubes suitable for welding and threading
• Tata Steel: EN 10255 conveyance tube dimensions and weights