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The hardened concrete's unit weight.
150 pcf is standard for normal-weight concrete; lightweight structural concrete is typically 90-115 pcf.
The concrete's specified 28-day compressive strength.
This formula is calibrated for f'c up to about 6000 psi; higher-strength concrete may need a different modulus formula per ACI 318.
Modulus of elasticity
3,830 ksi
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
- 26,436.27 MPa
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Concrete Elastic Modulus Calculator (ACI 318): 3,834 ksi — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- 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
Inputs used
- Concrete Unit Weight
- 150 pcf
- Compressive Strength (f'c)
- 4000 psi
Intermediate steps
- Equivalent in MPa
- 26,436.27 MPa
Confidence note: 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.
What this calculation does not cover
- The formula reads only unit weight and specified strength. It carries no information about aggregate type or stiffness, which is the main reason two mixes at the same weight and strength measure different moduli — the ACI expression is a best fit through scattered test data, not a property of your mix.
- It assumes the specified 28-day strength has been reached. Nothing here allows for age at loading, curing history, moisture condition, or in-place strength from cores and cylinders; concrete loaded early is meaningfully less stiff than this figure.
- This is a short-term elastic modulus. It does not include creep, shrinkage, or sustained-load effects, and it says nothing about cracked-section behaviour — a deflection check on a reinforced member needs a cracked or effective stiffness and a long-term multiplier applied on top of this number.
- The expression covers unit weights of roughly 90 to 160 pcf (1,440 to 2,560 kg/m³), so it does not apply to heavyweight or shielding concrete. The strength field accepts up to 12,000 psi (83 MPa) even though the formula is calibrated for normal-strength concrete; above about 6,000 psi (41 MPa) it tends to read stiffer than tests on high-strength mixes, and no warning is raised.
- This is an estimate, not a measured or design value. Where deflection, camber, prestress loss or vibration governs, the modulus has to come from ASTM C469 testing on the actual mix, and its use in a structural check is the engineer of record's call.
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This result is a specification — 3,830 ksi — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.2.1
Regulatory standards & verification citations1
- 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
Which documents these citations point at
Standards referenced: ACI 318 (American Concrete Institute, United States).
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