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Dust Collector CFM & Duct Sizer

Size a single-stage or two-stage dust collector for your shop — by tool count, duct length, and number of machines running at once.

Calculator

Planer 600+, jointer 350, table saw 350, miter saw 200.

Each 90° adds ~10 ft equivalent length.

What makes this different

Generic 'shop size → CFM' charts ignore duct resistance, which is the actual bottleneck. This one lets you enter duct length, number of fittings (each adds equivalent length), and CFM per tool — then computes total static pressure loss and required collector CFM.

Who it's for & when to use it

Sizing a new dust collector, troubleshooting weak suction at the planer, deciding if you need a bigger blower.

How to use

  1. Enter the dimensions of your material or the parameters of your project.
  2. Adjust the optional knobs (waste factor, kerf, planer allowance) to match your shop practice.
  3. Click Calculate and read the output. Use the per-item breakdown for ordering, the totals for budgeting.
  4. Compare the result to your lumber yard's quote — the effective $/BF column is the apples-to-apples number.

Formula: Equivalent duct length = straight ft + 10 × fittings. CFM required = sum of tool CFM. Velocity target ≈ 3,500–4,000 fpm for fine dust.

Notes & tips from the shop

  • Static pressure loss, not CFM, is usually the limit. A long, narrow duct on a small blower gives up before CFM does.
  • 6 in main duct is the practical minimum for a small shop; 8 in for shops with more than one heavy machine.
  • Always run the largest machine alone when sizing — the planer alone often draws more than all the others combined.

Frequently asked questions

Why is suction weak at the planer?

Usually duct length or fittings, not the collector. Try a shorter, straighter duct or a larger diameter before buying a bigger blower.

Do I need a cyclone separator?

For any collector under 1,500 CFM, yes — it cuts filter clogging dramatically.

What's a 'high-static' blower?

Higher static pressure at the same CFM — designed for long duct runs. Worth the cost if your shop is laid out long.

Limitations

Single-duct model. Branch circuits and blast gates not modeled — those change CFM at each tool depending on what's open.

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