Return Air Grille Size Calculator

Return air grille sizing converts CFM and target face velocity into required free area, then adjusts for grille free-area ratio.

Open grille size calculator Size connected duct

return air grille size calculator return air grille size by cfm supply register sizing by cfm chart

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Required free area

A_free = Q / face velocity

Nominal grille area

A_nominal = A_free / free_area_ratio

Installed check

v_installed = Q / (width * height * free_area_ratio)

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