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Concrete unit weight calculator: density, yield and air content (ASTM C138)
Enter the measure volume, the empty measure mass and the measure filled with concrete to get the density. Add the total batch mass for yield, the design batch volume for relative yield, and the theoretical density from the mix design for gravimetric air content.
By ProofGrit Editorial TeamLast reviewed:
Results update as you typeUnits: pcf, lb, ft³, %Runs in your browser. Nothing is saved.
Key takeaways
- Density needs only the measure volume and two weighings.
- Yield and relative yield need the total batch mass and the design volume.
- Gravimetric air content needs the air-free theoretical density from the mix design.
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How it's calculated
How is the result calculated?
D = (Mc − Mm) ÷ Vm; Y = W ÷ D; relative yield = Y ÷ design volume; A = (T − D) ÷ T × 100.
- 01Density (unit weight) D = (Mc − Mm) ÷ Vm, with Mc = measure filled with concrete, Mm = empty measure (lb) and Vm = measure volume (ft³)
- 02Yield Y = W ÷ D (ft³), with W = total mass of all materials in the batch (lb); divide by 27 for cubic yards
- 03Relative yield = Y ÷ the volume of concrete the batch was designed to produce
- 04Gravimetric air content A = (T − D) ÷ T × 100, with T = theoretical density of the concrete on an air-free basis
- 05Density is shown to 0.1 pcf, air content to 0.1 % and yield to 0.01
Rounding: density to 0.1 pcf, air content to 0.1 %, yield and relative yield to 0.01. Full precision is kept between steps.
FAQ
Frequently asked questions about the concrete unit weight calculator
Is unit weight the same as density?
Yes. ASTM C138 uses density (unit weight) for the mass of fresh concrete per unit volume, in pcf in US customary units.
What does relative yield tell me?
Whether the batch produced the volume it was designed for. A value below 1 means less concrete than designed; above 1 means more.
Where does the theoretical density come from?
From the mix design: the total mass of the batch materials divided by their absolute volumes, with no air. Ask the mix designer or the producer for it.
Does gravimetric air replace a pressure meter test?
No. It is a calculated check. Air content is measured with ASTM C231 (pressure) or ASTM C173 (volumetric) as the project requires.
Do I need all the inputs?
No. The measure volume and the two weighings give density. Yield, relative yield and air content appear as you add the batch mass, design volume and theoretical density.
Related guides and pages
- Fresh concrete tests: slump, air, temperature and unit weightA plain-English tour of fresh concrete tests: sampling, slump, air content, temperature and unit weight, and why the field sheet matters later.
- Slump test: ASTM C143 field guideWhat the concrete slump test measures, how ASTM C143 results are recorded, and how to avoid confusing slump with strength or acceptance.
- ASTM C31: making and curing concrete cylinders in the fieldA walk-through of making and curing field cylinders, the initial curing temperature ranges, and how handling errors show up in acceptance results.
- Concrete testing softwareHow ProofGrit handles this test in the lab.
- Standards indexEvery standard explained on this site, with plain-English purpose.
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Sources and further reading
- ASTM C138/C138M, density (unit weight), yield and gravimetric air contentASTM International
- ASTM C172/C172M, sampling freshly mixed concreteASTM International
- ASTM C231/C231M, air content by the pressure methodASTM International
Standards are summarized in our own words. Read the current edition from the publisher before you test.
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