What Is an I Beam? Types, Sizes, Weight and Applications

An I beam is a structural steel section with a cross-section that resembles the capital letter “I.” It consists of two horizontal flanges connected by a vertical web. This shape allows the beam to carry bending and shear forces efficiently while keeping its structural weight relatively low.
I beams are widely used in building structures, industrial facilities, bridges, platforms, frames, and other load-bearing applications. Depending on the applicable standard, I-shaped steel sections may be identified by designations such as IPE, IPN, W shapes, or other regional section systems.

For engineers, contractors, and steel buyers, choosing an I beam involves more than simply selecting a beam by its overall height. The section depth, flange width, web thickness, flange thickness, cross-sectional area, mass per meter, steel grade, span, loading conditions, and applicable design standard all need to be considered.

What Does I Beam Mean?

The term I beam refers to the shape of the steel section.
Looking at the beam from its end, the two flanges form the top and bottom parts of the “I,” while the web connects them vertically.

I Beam Part	Meaning	Main Function
Top flange	Horizontal upper section	Helps resist bending
Web	Vertical central section	Transfers shear and connects the flanges
Bottom flange	Horizontal lower section	Helps resist bending
Root/fillet	Transition between web and flange	Reduces the sharp transition between sections

The exact geometry varies between section series. For example, published European I-beam data identifies overall depth, section width, web thickness, flange thickness, root radius, mass per metre, and other section properties as important design parameters.

How Does an I Beam Work?

The main structural advantage of an I beam comes from placing material away from the neutral axis of the section.
When a beam is subjected to bending, the flanges provide much of the resistance to bending, while the web plays an important role in carrying shear and maintaining the separation between the flanges.
This makes an I-shaped section an efficient way to obtain substantial bending resistance without using a solid rectangular block of steel.
However, a larger I beam is not automatically the correct choice for every application. Beam selection depends on the actual loading, span, support conditions, deflection requirements, lateral stability, connection design, steel grade, and applicable structural design code.
AISC notes that preliminary beam sizing depends on factors such as span, dead load, live load, serviceability, and other project-specific design parameters. Preliminary tables are not a substitute for engineering design.

What Are the Main Dimensions of an I Beam?

When reading an I beam size chart, several dimensions are particularly important.

Dimension	Symbol	Description
Overall depth	h	Total height from the bottom of one flange to the top of the other
Flange width	b	Overall width of the flange
Web thickness	tw	Thickness of the vertical web
Flange thickness	tf	Thickness of the horizontal flange
Root radius	r	Radius at the web-to-flange transition
Mass per meter	kg/m	Approximate weight of the section per metre

These dimensions are normally provided in an I beam dimensions chart or structural steel section table.
For example, British Steel section data lists depth, width, web thickness, flange thickness, root radius, mass per metre, and section properties for structural steel sections.

What Are Common Types of I Beams?

The term “I beam” covers several different section families and naming systems.

IPE Beams
IPE sections are European I-beam profiles commonly used in structural steel applications.
British Steel, for example, lists European I beams from IPE 100 through IPE 750, with steel grades including S235, S275, and S355 variants.
IPE beams are commonly specified using a designation such as:

IPE 200
The exact dimensions and mass must be checked against the relevant section standard rather than assumed solely from the designation.

IPN Beams
IPN is another European I-section family.
IPN sections have a different flange geometry from IPE sections, so an IPN designation should not be treated as interchangeable with an IPE designation of the same nominal depth.
When purchasing, always identify the exact section series required by the project drawings or specification.

W Shapes
In the United States, many structural members that visually resemble I beams are specified as W shapes, also known as wide-flange sections.
For example: W12 × 26
In this designation, “W” identifies the wide-flange shape, “12” represents the nominal depth in inches, and “26” represents the nominal weight in pounds per foot. AISC also notes that the actual dimensions can differ from the nominal designation.
This distinction is important when working with international customers because I beam, IPE, IPN, and W-shape terminology should not be mixed without checking the applicable standard.

I Beam Size and Weight
I beam sizes are commonly specified using a combination of section designation, dimensions, and mass.
A typical I beam size chart may include:

Item	Typical Information
Section designation	IPE 200, IPE 300, etc.
Overall depth	mm
Flange width	mm
Web thickness	mm
Flange thickness	mm
Mass	kg/m
Cross-sectional area	cm²
Moment of inertia	cm⁴
Section modulus	cm³

The mass per metre is particularly useful for steel purchasing because it allows buyers to estimate the theoretical weight of a required beam length.

How Is I Beam Weight Calculated?

For a simple purchasing estimate:
Total theoretical weight = Mass per meter × Length
For example, if a specified section has a theoretical mass of 30 kg/m and the required total length is 12 m:
30 kg/m × 12 m = 360 kg

For commercial orders, however, the actual supplied weight should be determined according to the applicable product standard, dimensional tolerances, and the supplier's commercial terms.

I Beam Standards and Steel Grades

I beams are manufactured according to different standards depending on the market and project requirements.
For European sections, common designations include IPE and HE, while American structural steel commonly uses W shapes and other ASTM/AISC-defined sections.
For example, British Steel lists European IPE sections in grades including S235, S275, and S355, while its American wide-flange range includes grades such as A992 and A572 Grade 50.
The steel grade should never be inferred only from the beam designation.
When preparing an RFQ, clearly state:
IPE 300, S355, 12 m, 20 pieces
The final specification should be checked against the applicable project standard before ordering.

Common Questions About I Beams

Is an I beam the same as a steel beam?
No. I beam describes a particular cross-sectional form of structural beam. Steel beams can have many different shapes, including I-shaped, H-shaped, channel, angle, box, and other sections.
Why is an I beam shaped like an I?
The I-shaped geometry places structural material efficiently around the central web, helping the section resist bending while avoiding the unnecessary weight of a solid rectangular section.
Are I beams strong?
I beams can provide efficient structural performance, but “strong” depends on the specific section, steel grade, span, loading, support conditions, and design requirements.
AISC's preliminary sizing guidance specifically notes that beam selection depends on project-specific loading and serviceability conditions.
What is the difference between IPE and IPN?
IPE and IPN are different European I-section families with different geometries. They should not be treated as interchangeable simply because their nominal depths are similar.
What does W12 × 26 mean?
In the U.S. structural steel system, W12 × 26 identifies a wide-flange beam with a nominal depth of approximately 12 inches and a nominal mass of 26 lb/ft. The actual dimensions should be obtained from the applicable section table.
How do I calculate the weight of an I beam?
Multiply the theoretical mass per meter by the required length:
Weight = kg/m × total length
For procurement, verify the applicable standard and tolerance requirements before using the calculation for commercial quantities.
Is an I beam suitable for a column?
Some I-shaped or wide-flange sections can be used as columns, but the suitability depends on the structural design. Column selection involves compression, buckling, effective length, section properties, connections, and other factors.
How do I choose an I beam for a building?
Start with the structural design requirements, including span, loads, deflection limits, support conditions, steel grade, applicable design code, and connection details. A structural engineer should verify the final member selection.

I Beam vs H Beam: What Is the Difference?

An I beam typically has narrower flanges, while an H beam has wider flanges and a broader cross-section, making their structural properties and applications different.

Conclusion

An I beam is a structural steel section consisting of two flanges connected by a vertical web. Its I-shaped geometry makes it useful for carrying bending and shear forces in many structural applications.
When selecting an I beam, the most important information is not simply whether the section “looks like an I.” Buyers and engineers should identify the section series, dimensions, mass, steel grade, applicable standard, loading conditions, span, and project requirements.
For general reference, an I beam size chart can help identify available sections, while an I beam weight chart can help estimate theoretical material quantities. For actual structural applications, final member selection should be verified by a qualified structural engineer.
BAOWI Steel can supply structural steel sections according to project requirements, including specified dimensions, grades, lengths, standards, and documentation.