What Size Dust Collector Do I Need?

Select the tools in your shop. The calculator sizes for your single largest tool, not the sum of all of them, because a blast gate sends full airflow to one machine at a time. Figures are recommended CFM, which includes margin for duct losses and fine dust capture, not just visible chip pickup.

1 HP vs 2 HP, in plain terms

A 1 HP single-stage collector is rated around 650 CFM by the manufacturer, but delivers closer to 420 CFM through six feet of 4 inch flex hose once real-world losses are accounted for, and less than 300 CFM at 25 feet. A 1.5 HP unit rated near 1,200 CFM tends to deliver roughly 470 to 500 CFM under the same conditions. The gap between the rated number and the delivered number is the single most common source of disappointment when sizing a collector, and it is why this calculator uses recommended, not rated, figures.

Full CFM reference chart

These are recommended, not bare minimum, figures, cross-checked against Oneida's and Woodcraft's published sizing guidance. Your actual duct run, number of elbows, and hood design will shift the real number. When in doubt, size up, since a collector that is slightly oversized is a minor cost, and one that is undersized never catches fine dust properly no matter how the ductwork is tuned.