Abstract: An airflow measuring assembly and method for an air handling system, such as an HVAC system. The assembly is constructed and arranged to direct a measurable air stream to quantify airflow through an air handling system. The assembly includes a plate structure with at least one aperture and airflow sensors. The assembly is adapted for placement in a slot of an air handler and may simulate the flow resistance of HVAC filters. The airflow sensors may be positioned with respect to the plate structure to provide averaged total and static pressure signals. A manometer may be connected to the assembly to provide pressure differential readings and which may be converted via mathematic formulas to provide the volumetric airflow rate through the air handling system.