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Concrete Unit Weight (Density) Calculator (ASTM C138)

Compute fresh concrete's unit weight from a standard measure-volume test, per ASTM C138.

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 2026-08-27 · v1.2.0

Market
Imperial · sales tax

Unit weight

151.61 pcf

High confidence
Net concrete mass
37.48 lb
Equivalent in pcf
151.61 pcf

With the figures above, the unit weight comes to 2429 kg/m³. 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 — 151.611 pcf — 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

  • ASTM C138 unit weight test: unit weight = (mass of measure filled with concrete - mass of empty measure) / volume of the measure

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Frequently asked questions

What is unit weight used for?
It's used to compute the batch's actual yield (see the Concrete Yield Calculator) and to verify the mix matches its design density, particularly important for lightweight or heavyweight concrete.
How does this differ from air content testing?
They use related but separate procedures — unit weight (ASTM C138) measures overall density, while a pressure air meter (ASTM C231) measures entrained air content directly; unit weight alone can't isolate air content without knowing the theoretical air-free density.
What's a typical unit weight for normal concrete?
About 2,240-2,400 kg/m³ (140-150 pcf) for normal-weight concrete; lightweight structural concrete is commonly 1,440-1,840 kg/m³ (90-115 pcf).