Bending Stress Calculator

In our bending stress calculator, enter your bending moment in pound-feet (lb-ft) and section modulus in cubic inches (in³). For example, enter 1000 for a 1,000 lb-ft moment and 10 for a 10 in³ section modulus.

The calculator displays the stress in both psi (pounds per square inch) and ksi (kips per square inch), along with the converted moment value from lb-ft to lb-in.

Given: M = 500 Nm, I = 0.005 m⁴, y = 0.1 m

Calculation: σ = (500 * 0.1) / 0.005 = 10,000 N/m²

Result: σ = 10,000 Pa

Bending Stress Formula

σ = (M * y) / I

Where:

• σ = Bending Stress (N/m² or Pascals)
• M = Bending Moment (Nm)
• y = Distance from the Neutral Axis (m)
• I = Moment of Inertia (m⁴)

• σ = M/S
• M = Moment × 12 (converting lb-ft to lb-in)
• S = Section Modulus
• σ = Stress in psi

Parameters

• M: Bending moment in lb-ft (converted to lb-in)
• S: Section modulus in cubic inches (in³)
• 12: Conversion factor from lb-ft to lb-in
• 1000: Conversion factor from psi to ksi

For a moment of 1,000 lb-ft and modulus of 10 in³:

Convert moment to 12,000 lb-in (1,000 × 12). Calculate stress as 12,000/10 = 1,200 psi or 1.2 ksi.

This represents the internal stress the beam experiences under the given loading condition.

How to Calculate Bending Stress?

To find the bending stress, first convert the bending moment from pound-feet to pound-inches by multiplying by 12. Then divide this value by the section modulus.

With a moment of 500 lb-ft, multiply by 12 to get 6,000 lb-in. If the section modulus is 5 in³, divide 6,000 by 5 to get 1,200 psi bending stress.

What is Bending Stress?

Bending stress is the internal force per unit area that develops within a material when subjected to a bending load. It occurs whenever a beam or similar structural element experiences a moment or couple forces that cause it to bend. The stress varies through the section, with maximum values occurring at the outer fibers of the beam.