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Concrete Evaporation Rate Calculator

Estimate concrete surface moisture evaporation rate to check plastic shrinkage cracking risk before a pour.

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 2026-08-26 · v1.1.0

Market
Imperial · sales tax

Estimated evaporation rate

0.54 kg/m²/hr

High confidence

Below the critical threshold under these conditions — standard curing practices should be adequate, though conditions can change during a long pour, so re-check if temperature or wind picks up.

Critical threshold
1 kg/m²/hr

Conditions are favorable for a standard cure, but evaporation risk can change quickly if wind picks up or humidity drops during a long pour — recheck this calculator against updated conditions if the placement runs long.

Add the equipment this sizes

This result is a specification — 0.537 kg/m²/hr — 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 305R / Uno metric evaporation equation: E = 5 x ([Tc+18]^2.5 - r x [Ta+18]^2.5) x (V+4) x 10^-6, with E in kg/m2/h, temperatures in degrees C and wind speed in km/h
  • Widely cited critical threshold: evaporation rate at or above approximately 0.2 lb/sq ft/hr (1.0 kg/m²/hr) significantly raises the risk of plastic shrinkage cracking

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Frequently asked questions

Why does wind matter so much more than I'd expect?
Wind continuously replaces the humid air layer right above the concrete surface with drier ambient air, dramatically accelerating moisture loss — this is why job sites often erect temporary windbreaks around large slab pours in exposed, breezy locations.
What is plastic shrinkage cracking?
When surface water evaporates faster than bleed water can rise to replace it, the surface shrinks while the concrete below is still plastic (not yet hardened), causing shallow cracks — usually cosmetic but sometimes affecting durability, and preventable with proper curing precautions.
What should I do if the rate is critical but I can't reschedule the pour?
Common mitigations include fogging the surface with a fine water mist (not flooding it), applying an evaporation-retardant admixture, erecting windbreaks and sunshades, and finishing/curing as promptly as possible after placement.
Is concrete temperature the same as air temperature?
No — fresh concrete generates heat from the cement hydration reaction and is often several degrees warmer than the surrounding air, especially in the first few hours, which is why this calculator asks for both separately.