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Concrete Bag Calculator

Estimate how many bags of pre-mixed concrete you need for fence post footings or small pours.

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 2026-08-25 · v1.0.0

Market
Imperial · sales tax
0.98 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Concrete bags needed

14 x 60 lb bags

High confidence
Total concrete volume
5.99 ft³

For the dimensions entered, expect a concrete bags needed of 14 x 60 lb bags. Note that number of posts sits at the low end of the range this calculator was checked against, so treat the output as indicative rather than settled. 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

  • Standard published yields for pre-mixed concrete: a 40 lb bag yields about 0.30 cubic ft, a 60 lb bag about 0.45 cubic ft, and an 80 lb bag about 0.60 cubic ft
  • Post footing volume = pi x radius² x height, per post

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

Do I need to subtract the post's own volume from the hole?
For most fence and deck posts the post's cross-section is small relative to the footing, so it's commonly ignored — for very large posts, subtract the post's own volume from each hole's volume for a more precise estimate.
Should I mix my own concrete instead of using bags?
For a handful of post footings, bagged pre-mix is usually more convenient than ordering a truck; for many footings or larger pours, bulk-mixed or truck-delivered concrete becomes more cost-effective — see the Concrete Calculator for slab-scale pours.
Does bag size affect total cost efficiency?
Larger bags (80 lb) generally have a lower cost per cubic foot of yield than smaller bags, but require more physical effort to lift and mix — factor in what you can safely handle.