HVAC Ductulator Calculator

Size a duct like the paper wheel, in two taps. Enter CFM and your friction rate and get the next standard round size up, with the velocity and the real friction at the size you'll buy. No fractional answers. Sizes come from the snap-lock, spiral or flex list, and rectangles round up to even inches so the shop can fab them. The math is the handbook's: ASHRAE Darcy friction with Colebrook, Huebscher equivalents, standard air. Every result shows how it got there. FREE, NO LIMITS • Size a duct by the equal-friction method, with an optional Manual D velocity limit per run (supply or return, trunk or branch) • Check an existing round or rectangular duct: velocity, friction and equivalent diameter • Round to rectangular for any duct depth, with aspect-ratio warnings past 3:1 and 4:1 • US units (CFM, in, fpm, in/100 ft) or metric (L/s, mm, m/s, Pa/m) PRO, ONE-TIME PURCHASE • Job sheets: save…