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Concrete Elastic Modulus Calculator (ACI 318)

Estimate a concrete mix's modulus of elasticity from its unit weight and compressive strength.

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

Modulus of elasticity

3834.25 ksi

Check your inputs

This is an estimate from a standard empirical formula — actual elastic modulus varies by aggregate type and should be measured directly (ASTM C469) for critical deflection-sensitive designs.

Equivalent in MPa
26436.27 MPa

Running these inputs gives 3834 ksi as the modulus of elasticity. Expect some drift against the real job; the calculation is solid but conditions on site are not. Currently reading for United States under IRC 2024 — pick a different market above and the figures re-cast accordingly.

Add the equipment this sizes

This result is a specification — 3,834.255 ksi — 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

  • ACI 318 Section 19.2.2: Ec = 33 x wc^1.5 x sqrt(f'c), where Ec and f'c are in psi and wc (unit weight) is in pcf, valid for wc between 90 and 160 pcf

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

What is the elastic modulus used for?
It's needed to calculate deflections, stiffness, and how load distributes between concrete and steel in composite or reinforced sections — a stiffer (higher modulus) concrete deflects less under the same load.
Why does unit weight matter so much for elastic modulus?
Lightweight concrete (using lightweight aggregate) is inherently less stiff than normal-weight concrete of the same strength, because the aggregate itself is more porous and compressible — the wc^1.5 term captures this effect.
Is this formula accurate for high-strength concrete?
It's calibrated for typical normal-strength ranges — for f'c above roughly 6000-8000 psi, ACI 318 and ACI 363 provide separate, more accurate modulus formulas for high-strength concrete.