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Drilled Pier Concrete Volume Calculator (Straight Shaft / Belled)

Estimate the concrete volume for a drilled shaft foundation pier, with an optional under-ream (bell) at the base.

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
1.97 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Total concrete volume

2.96 yd³

Check your inputs

Assumes an idealized frustum-shaped bell — actual drilled bell geometry can vary with the drilling equipment and soil conditions; verify final volume against the driller's as-built log.

Straight shaft volume
2.96 yd³
Bell volume
0 yd³

For the dimensions entered, expect a total concrete volume of 2.26 m³. Of the working steps, straight shaft volume dominates at 2.26 m³. Moderate confidence — sound arithmetic, but allow for the variation any real site introduces. Set for United States against IRC 2024. The market selector changes both the units and the code cited.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

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

  • Straight shaft volume = pi x radius² x length; an under-ream (bell) is a frustum of a cone, volume = (pi x height / 3) x (R² + Rr + r²), where R is the bell radius and r is the shaft radius

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Frequently asked questions

Why use a belled pier instead of a wider shaft throughout?
Belling only the base spreads load over a larger bearing area without the cost and difficulty of drilling and casing a wider hole for the entire shaft length — useful in soils where a modest shaft diameter is adequate for skin friction but end bearing needs a larger area.
Is belling always possible?
No — bells require cohesive soil that can hold an unsupported overhang shape during drilling; granular or unstable soils generally can't be belled safely and need a straight shaft or casing instead.
Does this include a reinforcement cage?
No — this is concrete volume only. See the Rebar Calculator for cage steel.