Free concrete tool
Concrete Evaporation Rate Calculator
Estimate the surface evaporation rate of a fresh concrete pour with the ACI 305 equation, so you know when plastic shrinkage cracking is a real risk before the trucks show up.
What the evaporation rate calculator does
The concrete evaporation calculator takes four inputs — air temperature, concrete temperature, relative humidity, and wind speed — and returns the rate at which surface moisture leaves fresh concrete. Work in US units (°F, mph, lb/ft²/hr) or metric (°C, km/h, kg/m²/hr); MudHub converts and runs the ACI 305 equation either way.
ACI 305 equation
Deterministic implementation of the standard nomograph formula — the same math, without reading a chart in the truck.
Live weather import
Pull current conditions for the job site and see the nearest recognizable town, station distance, and observation time.
Risk guidance
Results are compared against the 0.2 lb/ft²/hr precaution threshold so the call is obvious on site.
Saved to the project
Store the snapshot with the job. Reopening it preserves the original values and conditions.
Concrete Evaporation Rate Calculator
Enter air temperature, concrete temperature, relative humidity, and wind speed to get the ACI 305 surface evaporation rate. Free, no sign-up required.
Surface & Weather Conditions
Range -40 to 140 °F
Always entered or confirmed manually
Range 0 to 100 %
Range 0 to 100 mph
Notice: This calculator estimates evaporative conditions using entered or imported weather data. It is a planning aid and not a direct measurement of actual concrete surface water loss. Verify job-site conditions, project specifications, and applicable industry guidance before placement.
Why evaporation rate matters on a pour
When water leaves the surface faster than bleed water rises, the top of the slab shrinks against concrete that has not moved yet, and plastic shrinkage cracks open before final set. Hot air, low humidity, and wind all push the rate up — wind is often the biggest factor, which is why a mild, breezy day can be worse than a still, hot one.
Running the numbers before the pour tells you whether to schedule earlier, set windbreaks, arrange fogging, or have an evaporation retarder on the truck.
Pairs with the rest of your pour planning
The evaporation calculator lives alongside the other concrete calculators and the joint layout calculator, so volume, saw cut schedule, and curing conditions all sit on the same job.
Informational planning tool only. Curing decisions, code compliance, and final specifications remain the responsibility of the licensed contractor or engineer of record.
Frequently asked questions
- How do I calculate evaporation rate?
- The ACI 305 nomograph equation is E = 5 x [(Tc + 18)^2.5 - r x (Ta + 18)^2.5] x (V + 4) x 10^-6, where Tc is concrete temperature in Celsius, Ta is air temperature in Celsius, r is relative humidity as a decimal, and V is wind speed in km/h. MudHub runs the equation for you in either US or metric units.
- What evaporation rate is too high for concrete?
- ACI 305 flags a surface evaporation rate above 0.2 lb/ft2/hr (about 1.0 kg/m2/hr) as the point where plastic shrinkage cracking becomes likely and precautions are recommended. Low-bleed mixes can require precautions at lower rates.
- What lowers concrete evaporation rate on site?
- Windbreaks, fog misting, evaporation retarders, sunshades, cooling the mix, dampening the subgrade, and scheduling the pour for cooler hours all reduce surface moisture loss.
- Can I save an evaporation calculation to a job?
- Yes. Save the result to a project in MudHub and the original conditions are preserved, so you have a record of the weather at the time of the pour.