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Embodied Carbon in Concrete Calculator

Cradle-to-gate (A1-A3) carbon for a concrete element, and what replacing cement with GGBS or fly ash actually saves.

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 · v1.1.0

Market
Imperial · sales tax

Embodied carbon (A1-A3)

18800 kgCO₂e

Low confidence

Emission factors here are typical published ranges for orientation, not product data. A reportable assessment uses the supplier's own Environmental Product Declaration — the spread between two suppliers of the same nominal product routinely exceeds 30%.

Tonnes CO₂e
18.8 tCO₂e
Concrete
15000 kgCO₂e
Reinforcement
3800 kgCO₂e
Reinforcement share
20.21 %
Per m³ of element
376 kgCO₂e/m³
Saving against 100% Portland
0 kgCO₂e
Reinforcement mass
11023.11 lb

At the values currently entered, the embodied carbon (a1-a3) works out to 18800 kgCO₂e. The largest intermediate quantity is concrete, at 15000 kgCO₂e — check that step first if the total looks off. Note that concrete volume and custom factor (kgco₂e/m³) sit at the edge of the range this calculator was checked against, so treat the output as indicative rather than settled. Confidence on this run is low: check the result against a supplier quote or a professional before ordering or building. Figures are shown for United States, where IRC 2024 is the governing residential reference; switch the market above if you are building elsewhere.

Add the equipment this sizes

This result is a specification — 18,800 kgCO₂e — 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

  • EN 15804 modules A1-A3 define cradle-to-gate: raw material supply, transport to the plant, and manufacturing
  • Typical GWP ranges for structural concrete are drawn from published EPDs and the ICE database; product-specific EPDs vary widely around them
  • Cement clinker is the dominant contributor — roughly 90% of a plain concrete's A1-A3 figure comes from the Portland cement fraction

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 is cement replacement such a large lever?
Because almost all of concrete's carbon is in the clinker, not the aggregate or the water. Making Portland cement calcines limestone, and that chemical reaction releases carbon dioxide regardless of how the kiln is fired — it is not a fuel problem that cleaner energy solves. Substituting GGBS or fly ash for part of the cement removes that fraction of the clinker and its emissions with it.
What is the catch with high GGBS levels?
Early strength. A 70% GGBS mix gains strength considerably more slowly than plain Portland, especially in cold weather, which pushes out striking times and can extend the programme. On a fast-cycle frame that delay has its own cost, and sometimes its own carbon. It is a genuine engineering trade, not a free saving.
Should I trust the numbers in the dropdown?
Only for orientation. They are typical published ranges, and the spread between two suppliers of nominally identical concrete regularly exceeds 30% — larger than several of the savings people chase. For anything that will be reported, use the supplier's EPD for the specific mix from the specific plant, and enter it as the custom factor.
Why does reinforcement get its own line?
Because it is routinely a fifth or more of a reinforced element's total, and concrete-only figures quietly omit it. It also carries its own large choice: recycled electric-arc-furnace rebar sits several times below primary blast-furnace steel. The breakdown shows the reinforcement share so you can see whether your attention belongs on the mix or on the steel.