CFM (Cubic Feet per Minute) measures the volume of air moved by your dust collector. Higher CFM means more dust and chips are captured at the source. For effective dust collection, you need sufficient CFM at each machine—typically 350–450 CFM for most woodworking tools with a 4-inch port. Undersized CFM leads to clogged pipes and poor air quality.

The most common shop hose size is 4 inches—it fits standard dust ports on table saws, jointers, planers, and band saws. If you have a larger industrial collector (3+ HP), a 5-inch or 6-inch hose delivers better airflow. For small benchtop tools with 2.5-inch ports, use a 2.5-inch hose with an adapter. Always match your hose size to both the machine port and the dust collector inlet for optimal performance.

Each 90° elbow adds resistance equivalent to 6–10 feet of straight duct, while 45° elbows add about 3–5 equivalent feet. Wye branches contribute 5–8 equivalent feet. Too many fittings dramatically increase static pressure loss, reducing airflow. Minimize elbows by using gentle bends and 45° fittings whenever possible. Our calculator accounts for these losses in the equivalent duct length estimation.

A 4-inch duct can handle approximately 350–400 CFM at proper transport velocity (3,500–4,000 FPM). A 6-inch duct handles 800–1,000 CFM—more than double the capacity. If your total CFM demand exceeds 400, upgrading to 6-inch main ducts prevents bottlenecking. Many small shop collectors come with 4-inch ports, but for multi-machine systems, 6-inch mains with 4-inch drops to each machine offer the best balance of airflow and velocity.

Static pressure (measured in inches of water) represents the resistance to airflow in your duct system. Every component—straight ducts, elbows, branches, and the machine hood itself—adds resistance. Most small shop collectors are rated for 6–10 inches of static pressure. If your system's total static pressure loss exceeds the collector's rating, airflow drops significantly. Keeping duct runs short and minimizing fittings helps keep static pressure low.

Flexible hose is convenient but has 1.5–2× more friction loss than smooth rigid duct. For short machine connections (5–10 feet), flexible hose works well. For long main runs, use rigid metal or PVC duct to minimize resistance. If you must use flex hose for longer runs, go up one size (e.g., use 5-inch flex where you'd use 4-inch rigid) to compensate for the extra friction.

Most woodworking machines with 4-inch dust ports need 350–450 CFM at the port. Table saws, jointers, and planers typically require 400 CFM. Sanders need 300–400 CFM. Small benchtop tools with 2.5-inch ports need about 150–250 CFM. Our calculator includes preset CFM values for common machines—simply select your machine type and we'll use the recommended CFM automatically.

As a rule of thumb: 1–1.5 HP suits single-machine use with short hose runs (under 15 feet). 2 HP collectors handle small ducted systems serving 2–3 machines. 3–5 HP units are needed for larger shops with multiple machines and longer duct runs. Our calculator estimates the recommended blower power based on your total CFM demand and system resistance—use it as a starting point when shopping for a collector.

Manufacturer CFM ratings are often measured at the impeller inlet with no duct attached. Once you connect ducts, hoses, elbows, and a dust bag or filter, the actual airflow at the machine can drop by 30–50% or more. That's why our calculator factors in equivalent duct length and static pressure losses—to give you a realistic estimate of what your system can actually deliver.

Most stationary woodworking tools have 4-inch OD dust ports that accept 4-inch ID flexible hose. Some benchtop tools use 2.5-inch ports, while large industrial machines may have 5-inch or 6-inch ports. Measure the outside diameter of your machine's dust port—the hose should slide snugly over it. Adapters and reducers are widely available if your hose size doesn't match the port exactly.