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Underpinning Pit Excavation Volume Calculator

Estimate the total excavation volume for a sequential (alternating) underpinning pit program.

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
3.94 ft3.28 ft4.92 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Total excavation volume

11.77 yd³

Check your inputs

Doesn't include temporary shoring, dewatering, or the new underpinning concrete volume itself — this is excavation volume only.

Volume per pit
2.35 yd³

At the values currently entered, the total excavation volume works out to 9 m³. The largest intermediate quantity is volume per pit, at 1.80 m³ — check that step first if the total looks off. Note that number of pits sits at the low end of the range this calculator was checked against, so treat the output as indicative rather than settled. Confidence is moderate: the method is sound, but real materials and site conditions vary. Figures are shown for United States, where IRC 2024 is the governing residential reference; switch the market above if you are building elsewhere.

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

  • Underpinning is typically excavated as a series of individual pits beneath an existing footing; total excavation volume = pit count x pit length x pit width x pit depth

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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 is underpinning done in a sequence of small pits instead of one continuous trench?
Excavating a continuous trench beneath a loaded footing would remove its support all at once and risk collapse — a sequenced, alternating pit pattern (leaving unexcavated sections between active pits) keeps the existing footing adequately supported throughout construction.
How is pit sequence typically numbered?
A common pattern is '1-in-4' or '1-in-5' sequencing, where every 4th or 5th pit is excavated and underpinned first, then the process repeats for the skipped sections once the first set has cured — never excavating two adjacent pits at the same time.
Does this include the new underpinning concrete itself?
No — this is excavation volume only. Use a general concrete volume calculator for the new footing/pier concrete once each pit is ready to pour.