Chimney Flue Size Calculator
Free chimney tool

Chimney Flue Size Calculator

Enter the size of a fireplace opening or pick a stove to see the flue size and liner to plan for.

These tools give planning-level estimates from typical values. They are not quotes, designs or engineering, and results depend on your actual chimney, appliance, fuel, site conditions and local rules. Only a site visit can confirm what a project needs, and we give you a written scope and price before any work begins.

How it works

Four quick steps.

  1. 01

    Pick what you burn

    Open fireplace, wood stove, insert or gas appliance.

  2. 02

    Enter the size

    Fireplace opening in inches, or the stove flue collar size.

  3. 03

    Add the chimney height

    A taller chimney draws more strongly.

  4. 04

    Read the result

    A suggested flue size and a note on liners.

Tips

  • A flue that is too large cools the smoke and builds creosote. One that is too small chokes the draft.
  • Stoves and inserts are usually sized to the collar on the appliance.
  • A stainless liner can bring an oversized flue down to the right size.
Questions

About this tool.

Is this the final size?

No. It is a planning guide from common rules of thumb. We measure and confirm on site.

Why does flue size matter?

Smoke needs to stay hot and move quickly. The right size keeps the draft strong and the flue cleaner.

Can an existing flue be made smaller?

Yes, with a liner sized to the appliance.

Free estimate

Ready for a chimney you can trust?

Call us and we will visit, look closely at your chimney and give you a clear plan and a written scope.

Call NowFree Estimate