Steel H Beam Calculator

Beam Inputs

Beam depth h (mm)

Flange width bf (mm)

Flange thickness tf (mm)

Web thickness tw (mm)

Span length L (m)

Load type

Applied UDL (kN/m)

Used only for UDL case.

Point load P (kN)

Used only for point-load case.

Include beam self-weight in UDL

Yield strength Fy (MPa)

Elastic modulus E (GPa)

Density (kg/m³)

Factor of safety

Deflection limit ratio

Example: 360 means limit is L/360.

Example Data Table

Sizes shown as h×bf×tf/tw. Values are computed from the same formulas used above.

Example size	Area (mm²)	Mass (kg/m)	Self-weight (kN/m)	Ixx (mm⁴)
200×100×10/6 (mm)	3,080	24.18	0.237	20,982,667
250×125×12/7 (mm)	4,582	35.97	0.353	49,252,519
300×150×12/8 (mm)	5,808	45.59	0.447	88,709,184
350×175×14/9 (mm)	7,798	61.21	0.600	163,417,319
400×200×16/10 (mm)	10,080	79.13	0.776	277,596,160

Formula Used

Area: A = 2·bf·tf + (h − 2·tf)·tw
Second moment about strong axis: Ixx = [bf·h³ − (bf − tw)·(h − 2·tf)³] / 12
Section modulus: Sx = Ixx / (h/2)
Self-weight: wself = (A·ρ·g) (converted to kN/m)
Max moment: UDL: Mmax = w·L²/8, Point at midspan: Mmax = P·L/4
Bending stress: σ = Mmax / Sx
Allowable stress: σallow = Fy / FoS
Deflection: UDL: δ = 5·w·L⁴ / (384·E·Ixx), Point: δ = P·L³ / (48·E·Ixx)
Approx web shear stress: τ ≈ Vmax / [(h − 2·tf)·tw]

Assumes a prismatic beam, small deflection behavior, and a simple support condition.

How to Use This Calculator

Enter the beam geometry in millimeters (h, bf, tf, tw).
Enter span length in meters and select the load type.
For UDL, provide kN/m; for point load, provide kN.
Choose whether to include beam self-weight in the UDL case.
Set material values (Fy, E) and pick a safety factor.
Select a deflection ratio like L/360 for typical floors.
Press Calculate to view results above the form.
Download CSV or PDF for sharing and recordkeeping.

Steel H Beam Article

1) What an H beam section really represents

An H beam is modeled as two flanges and a central web. In this calculator, the cross‑section is treated as an outer rectangle minus the inner void, giving area A, second moment Ixx, and section modulus Sx. These values drive weight, stress, and deflection results.

2) Geometry inputs and practical ranges

Depth (h) has the strongest effect on stiffness because Ixx scales roughly with h³. Flange width (bf) increases lateral bearing and contributes to Ixx. Flange thickness (tf) and web thickness (tw) increase area and shear capacity, but also increase self‑weight.

3) Load cases supported by this tool

The calculator provides two common screening cases for simply supported beams: a uniformly distributed load (UDL, kN/m) and a midspan point load (kN). For UDL, maximum moment occurs at midspan (wL²/8). For a midspan point load, it is PL/4.

4) Self‑weight and why it matters

Self‑weight is computed from area A, density ρ, and gravity g, then expressed as kN/m. On shorter spans it may be minor compared with imposed loads, but for longer spans or light live loads, self‑weight can noticeably increase moment, shear, and deflection.

5) Stress calculation and utilization

Bending stress is calculated as σ = M/Sx and compared to an allowable stress σallow = Fy/FoS. The utilization ratio (σ/σallow) offers a quick capacity indicator. A utilization near 1.0 means you are close to the selected allowable limit under the chosen load case.

6) Deflection control and serviceability

Deflection is often the controlling check for floors and long beams. Under UDL, δ = 5wL⁴/(384EI). Under midspan point load, δ = PL³/(48EI). Because deflection scales with L³ or L⁴, modest span increases can create large serviceability changes.

7) Interpreting the example table

The example table lists sample sizes and reports area (mm²), mass (kg/m), self‑weight (kN/m), and Ixx (mm⁴). Use it to sense how depth increases stiffness quickly, while thickness increases weight more steadily. It is a fast way to compare candidates before detailed checks.

8) Good field workflow for beam selection

Start with estimated loads, then iterate several beam sizes. Aim for utilization comfortably below 1.0 and deflection within your chosen ratio (like L/360). Document span, support assumptions, load type, and safety factor, then confirm final design with code‑based checks and connections.

FAQs

1) Which units should I enter?

Enter dimensions in millimeters, span in meters, UDL in kN/m, point load in kN, Fy in MPa, and E in GPa. The tool converts internally for consistent calculations.

2) What does the utilization ratio mean?

Utilization is bending stress divided by allowable stress (Fy/FoS). Values below 1.0 indicate the beam meets the chosen allowable bending limit for the selected loading case.

3) Why does deflection change so much with span?

Deflection increases rapidly with span: proportional to L⁴ for UDL and L³ for a midspan point load. Small span increases can cause large deflection increases even when stress looks acceptable.

4) Should I include self‑weight?

For preliminary sizing, yes—especially on longer spans or lighter imposed loads. Self‑weight adds to UDL and increases both moment and deflection, which can change the pass/check outcome.

5) Is the shear stress result exact?

No. It is an average web shear estimate using the web area (h−2tf)·tw. Shear distribution is not uniform, so treat it as a screening value only.

6) Does the tool check buckling or lateral bracing?

It does not. Lateral‑torsional buckling, bearing, web crippling, and connection design depend on bracing, detailing, and code rules. Use this tool for early comparison and then verify formally.

7) What deflection limit ratio should I use?

Common starting points are L/360 for many floors and L/240 for some roof members, but requirements vary by code and finishes. Choose a ratio that matches your project criteria and comfort expectations.

Measure carefully, check assumptions, and document your final selection.