Fireplace Liner Sizing Guide

The standard 10-1 ratio has been used in the chart below.  To be safe, we recommend a 10-1 ratio for chimneys less than 25 feet in height and a 12-1 ration for chimneys greater than 25 feet in height.

Please contact us for other sizes or with any further questions.

Fireplace Opening

Up to 600 sq. in

Liner Size

9"
601 - 760 sq. in. 10"
761 - 942 sq. in. 11"
943 - 1140 sq. in. 12"
1141 - 1356 sq. in. 14"
1357 - 1846 sq. in. 16"








 

 

 

Liner Sizing Charts

Calculate the area needed for fireplace liners of various shapes:
 
Rectangle 1. Figure the opening for the fireplace (length x width)
2. Divide this number by 12
Circle Area = pi r2
Circumference = pi d
pi = 3.14
r = radius (half of diameter)
r2 = radius squared
d = diameter

Look at the charts below for round or ovalized liners.
Oval 1. Divide the shape into a rectangle and two half circles (1/2 circle on each end of the rectangle)
2. Figure the area for the rectangle
3. Then figure the area for the circle
4. Add the two amounts together.  This gives you the approximate area of the oval

Look at the charts below for round or ovalized liners.
Square Area = length (L) x width (W)
Triangle Area = length (L) x width (W) x 1/2

Use a liner size where the square inches for the liner is larger than the number you came up with.  This is the appropriate liner for this fireplace opening.

Area in Square Inches of ROUND Liners

3" 4" 5" 6" 7" 8" 9" 10" 11" 12"
7.07 12.56 19.63 28.26 38.46 50.25 63.58 78.5 94.99 113.14


Area in Square Inches of OVALIZED M-Flex Liners

Original
Size
of
Round
Liner
 12" 63 72 79 86 93 99 102 106 113
11" 57 65 72 78 83 87 92 95 *
10" 50 57 63 68 72 76 79 * *
9" 43 50 53 56 61 63 * * *
8" 36 42 45 48 50 * * * *
7" 32 34 36 38 * * * * *
6" 24 25 28 * * * * * *
5" 18 19 * * * * * * *
  4" 5" 6" 7" 8" 9" 10" 11" 12"
The Size of the Liner Ovalized To


Calculating the Dimension of the LARGER SIDE of an M-Flex OVALIZED Liner

Original
Size
of
Round
Liner
 12" 16.5" 16.2" 15.7" 15.4" 15.0" 14.5" 14.0" 13.0" *
11" 15.3" 14.8" 14.3" 13.6" 12.8" 12.0" 11.5" * *
10" 13.8" 13.3" 13.0" 12.5" 12.0" 11.3" * * *
9" 12.5" 12.0" 11.8" 10.8" 10.0" * * * *
8" 10.5" 10.3" 9.5" 9.0" * * * * *
7" 9.3" 8.8" 8.3" * * * * * *
6" 7.7" 7.0" * * * * * * *
5" 5.7" * * * * * * * *
  4" 5" 6" 7" 8" 9" 10" 11" 12"
The Smaller Side of the M-Flex Ovalized Liner
(the size the liner was ovalized down to)