How to Use This Tool
Convert a room's volume and target air-change rate into ideal volumetric airflow. Calculate CFM, cubic meters per hour, room volume and minutes per nominal air change from room dimensions and ACH.
The decision this tool supports
ACH is a normalized rate, while a fan is rated in airflow; choosing equipment requires converting between them on the actual room volume. This page keeps the decision bounded to ideal airflow and the supporting outputs shown beside it. ACH Airflow does not import an account, infer a market rate, or silently substitute an industry average.
Inputs and units
The ACH Airflow calculation uses Room length, Room width, Room height, Target air changes per hour. Keep all money values in one currency and all time, distance, mass, energy or volume entries in the unit printed beside the field. Mixing ACH Airflow scopes can produce a plausible number with the wrong meaning.
- Room length is entered in feet.
- Room width is entered in feet.
- Room height is entered in feet.
- Target air changes per hour is entered in ACH.
Formula and worked check
ACH = airflow per hour ÷ room volume, so CFM = room volume ft³ × ACH ÷ 60; m³/h converts CFM by 1.69901082. A 20 × 15 × 8 ft room is 2,400 ft³; six ACH corresponds to 240 CFM, 407.8 m³/h and one nominal air change every ten minutes. The ACH Airflow default is an executable known-answer case, not a benchmark or recommendation. Change one input and verify that the direction of ideal airflow still matches the stated relationship.
How to interpret the result
The result is ideal nominal airflow. Real fan selection must account for duct pressure, filter loading, mixing, outdoor-air fraction and required standard. The additional ACH Airflow outputs expose the denominator, comparison, capacity or reverse value needed to audit the primary result instead of presenting one unexplained number.
Assumptions
- Room is approximated as a rectangular volume.
- Target ACH is supplied from the applicable design requirement.
- Airflow is an ideal well-mixed volumetric rate.
Save the ACH Airflow input values and date with any material decision. A later ACH Airflow rerun is reproducible only when the same assumptions and units are available.
Limitations and safety boundary
This does not prescribe a safe ACH, calculate contaminant removal, certify ventilation, or size a fan under static pressure. ACH Airflow is an estimate and cannot replace a contract, local code, licensed professional, calibrated measurement, lender statement or platform report where one governs the decision.
Source and privacy
The ACH Airflow definition or rule was checked against ASHRAE Handbook — Ventilation and Infiltration on 2026-08-26. Recheck ASHRAE Handbook — Ventilation and Infiltration when a specification or policy behind ACH Airflow can change. ACH Airflow arithmetic runs in this browser tab; ecech does not receive the values through a calculation API.
Sources & assumptions
Tool Spec v2 · verified 2026-08-26. Platform rules and fees can change; the editable inputs remain authoritative for your account.
Official references
- ASHRAE Handbook — Ventilation and Infiltration (checked 2026-08-26)
Model assumptions
- Room is approximated as a rectangular volume.
- Target ACH is supplied from the applicable design requirement.
- Airflow is an ideal well-mixed volumetric rate.
- This does not prescribe a safe ACH, calculate contaminant removal, certify ventilation, or size a fan under static pressure.
