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Chimney Liner Length Calculator

Find out how many metres of flue liner you need and what it will cost.

How it is calculated

The liner has to cover the chimney height plus extra at both ends for the connections: liner length = H + a, with H the chimney height in metres and a the combined top and bottom connection allowance in metres (you enter it; the default is 1 m). Because liner is sold in whole metres, the tool rounds up: order = ceil(H + a). Cost is order × price per metre. Only the liner itself is priced; the top plate, cowl, connector and any fittings are not included. Height must be above zero, allowance and price can be zero but not negative.

Worked example

A chimney 7.3 m tall with a 1.2 m connection allowance and liner at 32 per metre. The liner length is 7.3 + 1.2 = 8.50 m. Liner is sold in whole metres, so 8.5 is rounded up and you order 9 m. The cost is 9 × 32 = $288.00. The rounding adds half a metre of spare liner, which is useful as a safety margin when feeding it down.

Try this example →

Common mistakes

  • Measuring the height of the stack from the roof only. The liner runs from the appliance outlet at the bottom, so measure the full flue path including the part inside the room.
  • Setting the allowance to 0 because the chimney looks straight. The top and bottom connections always use some length, so the default of 1 m is a better starting point.
  • Paying by the exact length shown. Liner is sold in whole metres, so the order line, not the liner length line, is the figure to buy and cost.
  • Expecting the total cost to include the cowl, top plate and connector. The tool prices only the liner, so add fittings from your supplier.
  • Entering feet where metres are asked. A 20 ft chimney is about 6.1 m, not 20.

About this calculator

A flexible chimney liner needs to run the full height of the chimney from the appliance connection at the bottom to above the chimney pot at the top, plus a connection allowance for the top and bottom ends, which you enter yourself — so ordering exactly the measured chimney height typically comes up short. Cost then follows directly from that length rounded up to whole meters multiplied by the price per meter; fittings like the top plate, cowl and connector are not included, so add them separately.

Homeowners installing a wood-burning stove or open-fire liner, and the HVAC or chimney technicians who fit them, use this calculation to order the correct liner length in one purchase, since flexible liner is typically sold by the meter and running short mid-installation means a costly second delivery — or worse, a joint partway up a flue where none should exist.

Chimney height plus the connection allowance gives the liner length to order, and the price per meter turns it into the total cost, so you can buy the right amount before work starts.

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