Compare board or beam deflection under consistent conditions

Match the support, load, material and cross-section, then compare how changing a dimension affects the calculated deflection.

Sketch the supports and the load first

Check whether the member is fixed at one end or supported at both ends. Decide whether the load acts at a point or is distributed. Different arrangements require different models even when the dimensions and material are unchanged.

Write down length, width and height separately. A sketch helps keep the cross-section orientation consistent with the way the member will be used.

Choose repeated comparison or detailed analysis

A formula and spreadsheet suit repeated calculations under one model. A structural tool such as SkyCiv provides more extensive analysis options. BENRI is useful for a quick estimate using the support and cross-section options shown in its diagrams.

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Compare methods for your task
Method	Useful for	What to consider
BENRI Beam Deflection Calculator	A quick visual comparison	Use a model matching the member you want to estimate
Formula and spreadsheet	Repeated comparisons using one model	Keep assumptions and units consistent
SkyCiv Beam	Beam analysis with specified conditions	Check support and load capabilities

BENRI Beam Deflection Calculator: Enter the model and inspect the result

Choose the support, load and section types using the diagrams.
Enter the dimensions and load, then choose the material.
Read self-weight, applied-load and total deflection. Larger deflections also appear in the diagram.
Change one condition and compare the numbers and shape to choose a dimension candidate.

For a distributed load, P is the total force across the beam. The support and load diagram helps check the arrangement.

Support, load and cross-section settings beside the calculated deflection — Choose the supports, load and cross-section, then inspect the deflection result. (Japanese interface.)

BENRI Beam Deflection Calculator: set conditions and calculate deflection ↗

Formula and spreadsheet: compare dimensions

Choose one support and load model, such as a rectangular cantilever with a tip force P.
Use mm for b, h and L, N/mm² for E and N for P. Calculate I=b×h³/12 and δ=P×L³/(3×E×I) in cells.
With b=50, h=50, L=1000, E=206000 and P=100, the result is about 0.31 mm. Compare rows that change only h.

Useful for many side-by-side candidates. This formula covers the tip load only, excluding self-weight; other supports or loads require a different formula.

Open the official instructions

SkyCiv Beam: model supports and loads

Create a beam model in SkyCiv Beam and set its units and length.
Define supports, section, material and the type, magnitude and position of each load.
Solve and inspect deflection results. Keep the units and assumptions consistent across alternatives.

Useful for modeling multiple supports and loads. Check the required features and plan, and compare consistent models.

Open the official instructions

Change one condition at a time

Hold length, load and material constant while changing the section height. Then compare materials at the same dimensions. This makes each effect easier to follow.

The steel cantilever example is 1,000 mm long, 50 mm wide and 50 mm high, with a 100 N tip load. It shows approximately 0.22 mm from self-weight plus 0.31 mm from the load, for a 0.53 mm total under those inputs.

Use the comparison to select a candidate

List each candidate’s dimensions, material and deflection. Use the differences to decide what to investigate next, such as a taller section or a shorter supported span.

Published: 2026-09-26

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