Span-to-Depth Sizing Calculator

Suggests a preliminary beam depth range from a span and support/composite condition, using typical UK structural practice ratios. This is a starting point only — always verify the actual section chosen using the Beam Analysis module.

Basis for this page:
  • Typical UK structural practice span-to-depth ratios for preliminary sizing — not a Eurocode clause. There is no EC3 formula for an initial target depth; this is commonly-used empirical guidance, similar in spirit to the deflection-limit guidance already used on the Beam Analysis page.
Accuracy & scope note:
  • This is a preliminary sizing aid only — it does not check bending, shear, or deflection capacity. Those checks are what the Beam Analysis module is for, and must always be run on the actual section chosen.
  • The ratios are typical/commonly-used figures, not a mandated or universally agreed standard. Different practices and different loading intensities can reasonably use different ratios — treat the suggested range as a starting point, not a target to hit precisely.
  • Composite ratios assume the beam acts compositely with a concrete slab via shear studs. If you haven't decided on composite action yet, use the non-composite ratios as the more conservative (deeper) starting point.
This tool provides preliminary, indicative guidance only, intended to assist with initial sizing. It is not a substitute for assessment by a qualified structural engineer, and cad-steel.co.uk accepts no responsibility for its use in any final design. Always verify the chosen section's capacity using the Beam Analysis module (and Column Buckling, if applicable) and have final designs checked and signed off by a suitably qualified and experienced structural engineer before construction.