Measure the inside of your fire pit opening, then choose a burner whose minimum opening is the same size as yours or smaller. Warming Trends publishes a minimum opening for every CROSSFIRE burner, from 18 inches round for the smallest to 74 by 14 inches for the longest linear, and the burner plate that caps the opening is sized to it. A 36 inch opening, for example, is the stated size for the CFBO320 at 320,000 BTU/hr and, in a square pan, the CFBST400 at 400,000 BTU/hr.
How do I measure my fire pit opening?
Measure the inside of the opening where the burner plate will sit, not the outside of the fire pit. For a round pit that is the inside diameter, for a square pit one inside side, and for a rectangular or linear pit the inside length and width. If the enclosure is not built yet, use the opening on the drawing and size the burner before the masonry or concrete goes in.
Then find your opening in the tables below. Each burner is listed at the minimum opening Warming Trends publishes for it, so any burner listed at your size or smaller will fit.
Which burner fits a round or square opening?
| Minimum opening | Burner | Family | BTU/hr | Pan shape | Flex lines | Plate |
|---|---|---|---|---|---|---|
| 18 in | CFBCTL120 | Circular Tree-Style | 120,000 | Round | One | ALPL18C |
| 18 in | CFBST120 | Square Tree-Style | 120,000 | Square | One | ALPL18S |
| 18 in | CFBO140 | Octagonal | 140,000 | Round or square | One | ALPL18C or ALPL18S |
| 24 in | CFBCTXL120 | Circular Tree-Style | 120,000 | Round | One | ALPL24C |
| 24 in | CFBO180 | Octagonal | 180,000 | Round or square | One | ALPL24C or ALPL24S |
| 30 in | CFB180 | Original | 180,000 | Round or square | One | ALPL30C or ALPL30S |
| 30 in | CFB240 | Original | 240,000 | Round or square | One | ALPL30C or ALPL30S |
| 30 in | CFBCT240 | Circular Tree-Style | 240,000 | Round | One | ALPL30C |
| 30 in | CFBO280 | Octagonal | 280,000 | Round or square | Two | ALPL30C or ALPL30S |
| 36 in | CFBO320 | Octagonal | 320,000 | Round or square | Two | ALPL36C or ALPL36S |
| 36 in | CFBST400 | Square Tree-Style | 400,000 | Square | Two | ALPL36S |
| 42 in | CFBO360 | Octagonal | 360,000 | Round or square | Two | ALPL42C or ALPL42S |
| 42 in | CFBCT440 | Circular Tree-Style | 440,000 | Round | Two | ALPL42C |
| 42 in | CFBST500 | Square Tree-Style | 500,000 | Square | Two | ALPL42S |
| 48 in | CFB350 | Original | 350,000 | Round or square | Two | ALPL48C or ALPL48S |
| 60 in | CFB450 | Original | 450,000 | Round or square | Two | ALPL60C or ALPL60S |
Plates ending in C are round and plates ending in S are square. Original and Octagonal burners take either; Circular Tree-Style is for round pans and Square Tree-Style for square ones.
Which burner fits a rectangular or linear opening?
| Minimum opening | Burner | Family | BTU/hr | Flex lines | Plate |
|---|---|---|---|---|---|
| 28 x 15 in | CFBH120 | H-Style | 120,000 | One | ALPL2815 |
| 34 x 17 in | CFBH160 | H-Style | 160,000 | One | ALPL3417 |
| 40 x 17 in | CFBH200 | H-Style | 200,000 | One | ALPL4017 |
| 46 x 17 in | CFBH240 | H-Style | 240,000 | One | ALPL4617 |
| 56 x 25 in | CFBH300 | H-Style | 300,000 | Two | ALPL5625 |
| 62 x 25 in | CFBH340 | H-Style | 340,000 | Two | ALPL6225 |
| 22 x 17 in | CFBDT160 | Double Tree-Style | 160,000 | One | ALPL2217 |
| 29 x 17 in | CFBDT240 | Double Tree-Style | 240,000 | One | ALPL2917 |
| 41 x 18 in | CFBDT320 | Double Tree-Style | 320,000 | Two | ALPL4118 |
| 50 x 18 in | CFBDT400 | Double Tree-Style | 400,000 | Two | ALPL5018 |
| 58 x 18 in | CFBDT480 | Double Tree-Style | 480,000 | Two | ALPL5918 |
| 20 x 11 in | CFBT110 | Tree-Style linear | 110,000 | One | ALPL2011 |
| 28 x 11 in | CFBT170 | Tree-Style linear | 170,000 | One | ALPL2811 |
| 36 x 11 in | CFBT230 | Tree-Style linear | 230,000 | One | ALPL3611 |
| 44 x 14 in | CFBT290 | Tree-Style linear | 290,000 | Two | ALPL4414 |
| 58 x 14 in | CFBT350 | Tree-Style linear | 350,000 | Two | ALPL5814 |
| 66 x 14 in | CFBT410 | Tree-Style linear | 410,000 | Two | ALPL6614 |
| 74 x 14 in | CFBT470 | Tree-Style linear | 470,000 | Two | ALPL7414 |
| 32 x 8 in | CFBL130 | Linear | 130,000 | One | ALPL328 |
| 38 x 8 in | CFBL150 | Linear | 150,000 | One | ALPL388 |
| 40 x 8 in | CFBL170 | Linear | 170,000 | Confirm | ALPL408 |
| 44 x 8 in | CFBL190 | Linear | 190,000 | One | ALPL448 |
| 50 x 10 in | CFBL210 | Linear | 210,000 | One | ALPL5010 |
| 56 x 10 in | CFBL250 | Linear | 250,000 | Two | ALPL5610 |
| 62 x 12 in | CFBL270 | Linear | 270,000 | Two | ALPL6212 |
H-Style spreads the flame across a wider rectangle, Double Tree-Style suits long pans about 17 to 18 inches wide, and Tree-Style linear and Linear burners make a single line of flame in narrow troughs.
Why does the opening matter more than the BTU number?
Because the BTU rating comes with the burner you choose, and the burner you can choose depends on the space it sits in. Each CROSSFIRE burner is rated for a minimum opening, and the burner plate that closes the gap around it is made to that opening. Start from the opening, then compare output among the burners that fit. Choosing more BTU than the opening is rated for does not make the fire bigger, it makes a burner that does not fit.
What else do I need to order with the burner?
The burner plate. It is a separate item and its part number follows the opening size. Each burner page names the plate it takes.
Natural gas or propane. Every burner comes as an NG or LP part number. The fuel is chosen when you order and the burner is not converted afterwards.
The flex line kit, or your own fittings. Each burner is offered with or without the FK1 kit, which includes a 36 inch by 3/4 inch flex line, two 3/4 inch flared fittings, a 3/4 inch key valve, a 3 inch and a 12 inch key, and a 1/2 by 2 inch nipple. Burners that take two flex lines need two connections.
A licensed gas technician. The gas supply has to be sized for the whole load and installed to the National Fuel Gas Code, ANSI Z223.1 and NFPA 54.
Questions we get about burner size
What size burner do I need for a 36 inch fire pit?
Two CROSSFIRE burners are made for a 36 inch opening: the CFBO320 Octagonal at 320,000 BTU/hr, which takes a round or square plate, and the CFBST400 Square Tree-Style at 400,000 BTU/hr for a square pan. Both take two flex lines. Burners listed for smaller openings, such as the CFB240 or the CFBCT240 for 30 inches and up, also fit and run on one flex line.
What size burner do I need for a 48 inch fire pit?
The CFB350 Original is listed for openings of 48 inches or larger, at 350,000 BTU/hr with the ALPL48C or ALPL48S plate. It takes two flex lines. For 60 inches and up the CFB450 at 450,000 BTU/hr is the next size.
Does a bigger BTU burner give me a bigger fire?
Only within the opening it was made for. Each burner is rated for a minimum opening, and that figure is what keeps the plate, the flame and the surrounding material in proportion. Choose from the openings in the tables first, then compare output among the burners that fit.
Do I need a burner plate?
Yes. The plate covers the opening around the burner and its part number follows the opening size, so ALPL4617 is the plate for a 46 by 17 inch opening. Each burner page names its plate, and it is ordered as a separate item.
What is the difference between one and two flex lines?
A burner with one flex line needs one gas connection. A burner with two needs two connections and a gas supply sized for the full load, which matters to your gas contractor before the enclosure is built. In most CROSSFIRE families the burners above 240,000 BTU/hr take two.
Can I order natural gas now and switch to propane later?
No. Natural gas and propane are separate part numbers, with an NG or LP suffix, and they are chosen when you order. Confirm the fuel at the site before ordering.
Not sure which one fits? Send us the inside dimensions of the opening and the fuel at your site, and we will reply with the burner, the plate and the number of flex lines.
Send us your measurementsSee all 43 burnersSources: minimum openings, BTU ratings, flex line counts, plates and kit contents are from the Warming Trends CROSSFIRE product listings at American Fire Features, read October 2026. Gas installation requirements from the National Fuel Gas Code, ANSI Z223.1 and NFPA 54. The product page governs if anything here differs.
