From this site

One project, every trade

Each calculator adds its lines to a single estimate — consolidated BOM, schedule and cash-flow included.

Open My Project →

Mixed Air (Economizer) Temperature Calculator

Calculate the resulting mixed-air temperature when outdoor air and return air combine in an air handling unit.

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

Resulting mixed air temperature

62.74 °F

High confidence
Total combined airflow
2000 CFM

Running these inputs gives 62.7 °F as the resulting mixed air temperature. Note that outdoor air cfm sits at the low end of the range this calculator was checked against, so treat the output as indicative rather than settled. Currently reading for United States under IRC 2024 — pick a different market above and the figures re-cast accordingly.

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

  • Mixed air temperature = (Outdoor Air CFM × Outdoor Air Temp + Return Air CFM × Return Air Temp) ÷ (Outdoor Air CFM + Return Air CFM), the standard air-stream mass-balance (weighted average) formula used in HVAC economizer and mixed-air control design.

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

How is mixed air temperature calculated?
It's a CFM-weighted average of the two air streams: (Outdoor Air CFM × Outdoor Air Temp + Return Air CFM × Return Air Temp) ÷ (Outdoor Air CFM + Return Air CFM). This is the standard air-stream mass-balance formula used in HVAC economizer and mixed-air control design.
Why does return air usually dominate the mixed air temperature?
Because the result is CFM-weighted, whichever air stream has the larger airflow volume pulls the mixed temperature closer to its own temperature — a return air stream with more CFM than the outdoor air stream will have more influence on the final mixed temperature.
What happens if both CFM values are zero?
With no airflow in either stream there is nothing to mix, so this calculator returns 0°F for that edge case rather than dividing by zero.