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Timber Post Bearing Area Calculator

Calculate the minimum bearing area required where a timber post bears on a beam, based on allowable perpendicular-to-grain stress.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Required bearing area

20.67 in²

High confidence

With the figures above, the required bearing area comes to 133 cm². This is calculated for United States and cites IRC 2024. Building in another market? Change the selector above so the units and code reference follow.

Add the equipment this sizes

This result is a specification — 20.667 in² — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Required bearing area = axial load ÷ allowable compression stress perpendicular to grain (Fc-perp), the standard NDS timber bearing check

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Frequently asked questions

Why is perpendicular-to-grain stress the governing check here, not parallel-to-grain?
Where a post bears on top of a beam (or a beam bears on a sill plate), the load crosses the grain of the supporting member — wood is significantly weaker in compression perpendicular to grain than parallel to grain, so Fc-perp of the supporting member typically governs the required bearing area.
What if the actual post cross-section is smaller than the required bearing area?
A bearing plate, larger post, or a cap block with a wider footprint is needed to spread the load over enough area to keep bearing stress within the allowable Fc-perp — bearing directly with an undersized post can crush the fibers of the supporting member over time.
Does the supporting member's species affect the allowable bearing stress?
Yes — Fc-perp values vary by wood species and grade and are published in the NDS supplement design value tables; always use the actual allowable value for the specific supporting member's species and grade rather than a generic assumption.