Steel Plate Thickness Calculator – Check Plate Adequacy in Seconds

In structural engineering, determining whether a steel plate is adequate to safely resist applied loads is essential for both strength and serviceability. The Steel Plate Thickness calculator helps engineers, designers, and students quickly evaluate if a plate can withstand bending and deflection under a uniformly distributed load

This easy-to-use online tool lets you input:

• Plate thickness (t) in mm
• Span length (L) in meters
• Material modulus of elasticity (E) in MPa
• Allowable fiber stress (σ) in MPa
• Steel density (γ) in kN/m³
• Applied load (W) in kN/m²
• Allowable deflection factor(L/?)(for example if L/100,then enter Allowable deflection factor as 100)

and get the following output:

• Maximum allowable load
• Maximum deflection
• Whether the plate thickness is sufficient under the applied load

Completely free, online, and ready to use – no downloads or registration required

How to Use the Calculator

1. Enter all required parameters in the input fields.
2. Click “Calculate”.
3. Instantly see the results: whether your steel plate passes stress and deflection checks.

This ensures your design meets safety and performance standards efficiently.

Use the calculator below to enter your plate parameters and instantly see if the thickness is sufficient. Ensure your design is safe, efficient, and code-compliant in seconds.

Step-by-Step Approach to Determining Steel Plate Thickness

When designing a steel plate subjected to bending under a uniform load, it is essential to ensure the plate can safely carry the applied forces without excessive deflection or risk of failure. The following steps provide a systematic method to calculate the required thickness of a steel plate for this purpose.

Plate Framing Considerations

To simplify the design, consider the plate as a one-way framed structure. Install beams in the longer direction at intervals of =< 0.5 Ly ) (where Ly is the longer dimension of the plate or floor). This arrangement effectively transforms the plate into a simple supported system on two beams.

Manual Design Calculation

For design purposes, consider a unit strip of the plate and perform the following calculations:

Moment of Inertia :

The moment of inertia of the plate is calculated based on its thickness using the formula:

Moment of inertia of 1-meter wide strip in mm⁴ = 1000*(Thickness of the plate in mm)^3 /12

Here; b= 1m = 1000mm

Section Modulus :

The section modulus is a geometric property that determines the bending strength of the plate. It is calculated as:

Section modulus of 1-meter wide strip in mm³ = 1000*Thickness of the plate in mm^2/6

Here; b= 1m = 1000mm

Self-Weight of the Steel Plate:

Self-weight of the steel plate is calculated as follows:
Self-weight of steel plate in KN/m² = Density of Steel in KN/m³ *Thickness of plate in mm/1000

Total Applied Load:

The total applied load on the plate includes both the self-weight of the plate and the maximum applied /external load. The total applied load is given by:
Total Applied load in KN/m² = Maximum Applied load in KN/m² +Self weight of steel plate in KN/m²

Maximum Allowable Deflection:

The maximum allowable deflection is typically specified as a fraction of the span length. In this case, use L/100 as specified in the code AISC for steel floors
Maximum allowable deflection in mm = Span length in meter *1000/100

Maximum Allowable Bending Moment per Unit Width:

The maximum allowable bending moment per unit width can be calculated using the allowable bending stress and the section modulus:
Maximum Bending moment per unit width in N-m/m = Allowable bending stress in Mpa * Section modulus of 1-meter wide strip in mm³ /1000
Here; Allowable bending stress = Fy/1.67 (As per the AISC code)

Allowable Uniform Load:

The allowable uniform load is calculated based on the maximum allowable bending moment :
Allowable uniform load in KN/m² = 8*(Maximum Bending moment per unit width in N-m/m *0.001)/(Span length in meter^2)

Actual Deflection:

The actual deflection of the plate can be calculated using the following formula:
Actual Deflection in mm = 5*Total Applied load *((Span length in meter*1000)^4)/(384*Modulus of Elasticity in Mpa*Moment of inertia of 1 meter wide strip in mm⁴ )

Design Checks

After performing the calculations, ensure the following conditions are met for the plate thickness to be considered sufficient for the applied uniform loading:

1. The total applied load must be less than or equal to the allowable uniform load.
2. The actual deflection must be less than or equal to the maximum allowable deflection.

If both conditions are satisfied, the selected plate thickness is sufficient to support the applied loads without excessive deflection or failure. If either condition is violated, the plate thickness must be increased.

Design Example

The following example is provided to enhance your understanding of the concept.

Data:

Thickness of Plate= 9mm

Spam lenth=1m

Modulus of Elasticity = 200000Mpa

Allowable Bending stress =150Mpa

Density of Steel = 78.5 KN/m²

Maximum Floor load = 5 Kn/m²

Calculation:

Moment of inertia = 1000*9^3/12 = 60750 mm⁴

Section Modulus = 1000*9^2/6 =13500 mm³

Self Weight of Steel Plate =78.5*9/1000=0.71 KN/m²

Total Load = 5+0.71 =5.71 KN/m²

Maximum allowable deflection =L/100 = 1*1000/100 =10mm

Maximum bending moment per unit width = 150*13500/1000 = 2025.0 N-m/m

Allowable Uniform load = 8*(2025*0.001) /(1)^2 = 16.20 KN/m²

Actual Deflection = 5*5.71*(1*1000)^4 /(384*200000*60750)=6.12 mm

The Design Calculation Sheet for this example is also attached below for your reference and better understanding.

Conclusion

Checking the steel plate thickness under uniform loading ensures both strength and deflection limits are satisfied. If the plate meets allowable stress and deflection criteria, it is safe and sufficient. Otherwise, increase thickness or adjust design parameters. This quick check helps engineers design safer, more efficient, and reliable steel structures.