How many bricks for a 36 inch fire pit?

16 modular bricks per course. Three courses (8 in high): 51 bricks; four: 68; five (13 in): 84; six: 101, all with 5% waste. Fire brick lining inside is another 14 per course.

How many bricks for a 48 inch fire pit?

21 modular bricks per course, so 89 for four courses and 111 for five with waste. A 48 inch pit is large: the ring is about 5 ft across the outside and needs a base of gravel or a paver circle to sit on.

How many bricks for a small 30 inch fire pit?

14 per course; 59 bricks for four courses, 74 for five. Thirty inches inside is the smallest comfortable fire; below that the flames lick the bricks and they spall.

How many retaining wall blocks for a fire pit?

Blocks are counted the same way: the circumference through the middle of the block divided by the block length. Many wall blocks are tapered for exactly this and the maker publishes blocks per ring for a given diameter; a typical 12 inch tapered block gives 10 to 12 per ring for a 36 inch pit. Use the calculator with the block length and depth.

Do I need fire bricks?

Yes for a wood fire you will use often: ordinary clay bricks and concrete blocks crack and spall with heat, fire bricks (refractory) do not. The usual build is an outer ring of face brick or block with an inner ring of fire brick laid with refractory mortar, and a steel ring insert is the alternative.

Dry-stacked rings work for tapered blocks and for a low pit; brick rings are better mortared, with refractory mortar on the fire-brick liner and ordinary mortar outside. Leave two or three unmortared vertical joints in the bottom course for air. Never seal a fire pit; trapped water turns to steam and breaks the bricks.

How many bricks do I need for a fire pit? 30, 36 and 48 inch

A round fire pit with a 36 inch inside diameter takes 16 standard modular bricks per course laid flat with their long side following the circle, so a 5 course pit about 13 inches high is 84 bricks with 5% waste. A 30 inch pit is 14 per course, a 48 inch pit 21. Line the inside with fire brick and add 14 of those per course. The tables cover 30 to 48 inches, 3 to 6 courses, square pits and the UK brick.

Open the brick and block calculator

Round fire pits: bricks per course and in total

Bricks laid flat, long side following the circle, joints of 3/8 inch (10 mm for the UK brick, 1/8 inch refractory mortar for fire brick). Per course is rounded up; totals add 5% for the odd cracked or cut brick. Height is the number of courses times the brick plus joint.

US modular 7 5/8 x 3 5/8 in, laid flat, 5% waste
Inside diameter	Per course	3 courses	4 courses	5 courses	6 courses
30 in	14	45 (8 in high)	59 (11 in high)	74 (13 in high)	89 (16 in high)
36 in	16	51 (8 in high)	68 (11 in high)	84 (13 in high)	101 (16 in high)
42 in	18	57 (8 in high)	76 (11 in high)	95 (13 in high)	114 (16 in high)
48 in	21	67 (8 in high)	89 (11 in high)	111 (13 in high)	133 (16 in high)

UK standard 215 x 102.5 mm, laid flat, 5% waste
Inside diameter	Per course	3 courses	4 courses	5 courses	6 courses
30 in	13	41 (9 in high)	55 (12 in high)	69 (15 in high)	82 (18 in high)
36 in	15	48 (9 in high)	63 (12 in high)	79 (15 in high)	95 (18 in high)
42 in	17	54 (9 in high)	72 (12 in high)	90 (15 in high)	108 (18 in high)
48 in	19	60 (9 in high)	80 (12 in high)	100 (15 in high)	120 (18 in high)

Fire brick 9 x 4.5 in, laid flat, 5% waste
Inside diameter	Per course	3 courses	4 courses	5 courses	6 courses
30 in	12	38 (8 in high)	51 (11 in high)	63 (13 in high)	76 (16 in high)
36 in	14	45 (8 in high)	59 (11 in high)	74 (13 in high)	89 (16 in high)
42 in	17	54 (8 in high)	72 (11 in high)	90 (13 in high)	108 (16 in high)
48 in	19	60 (8 in high)	80 (11 in high)	100 (13 in high)	120 (16 in high)

Square fire pits

Four straight sides with overlapping corners: each side is the inside length plus one brick depth, divided by the brick plus joint, and the courses alternate the overlap so the corners bond.

US modular brick, 5% waste
Inside side	Per course	3 courses	4 courses	5 courses	6 courses
36 in	20	63	84	105	126
42 in	24	76	101	126	152
48 in	28	89	118	147	177

How the numbers are worked out

Take the circle through the middle of the brick: inside diameter plus one brick depth. Its circumference (pi x diameter) divided by the brick length plus joint is the bricks per course, rounded up. For 36 inches with a modular brick: (36 + 3.625) x 3.1416 / (7.625 + 0.375) = 15.6, so 16. Times the courses, plus 5%. The brick calculator gives the count for a wall; for a ring use the formula above or enter the ring as a wall of length = circumference and height = courses.

Before you build

Base: dig out 6 inches, fill with compacted gravel, or set the pit on a paver circle; the paver guide and the base guide cover the patio around it.
Keep the pit at least 10 ft from the house, fences and overhanging branches, and check local rules on open fires.
Fire brick goes in with refractory mortar, not ordinary mortar, and the wall can be capped with a course of pavers or flat stone for a seat.
Bricks for a straight wall or a patio are in the bricks per square foot guide.

Frequently asked questions

How many bricks for a 36 inch fire pit?: 16 modular bricks per course. Three courses (8 in high): 51 bricks; four: 68; five (13 in): 84; six: 101, all with 5% waste. Fire brick lining inside is another 14 per course.
How many bricks for a 48 inch fire pit?: 21 modular bricks per course, so 89 for four courses and 111 for five with waste. A 48 inch pit is large: the ring is about 5 ft across the outside and needs a base of gravel or a paver circle to sit on.
How many bricks for a small 30 inch fire pit?: 14 per course; 59 bricks for four courses, 74 for five. Thirty inches inside is the smallest comfortable fire; below that the flames lick the bricks and they spall.
How many retaining wall blocks for a fire pit?: Blocks are counted the same way: the circumference through the middle of the block divided by the block length. Many wall blocks are tapered for exactly this and the maker publishes blocks per ring for a given diameter; a typical 12 inch tapered block gives 10 to 12 per ring for a 36 inch pit. Use the calculator with the block length and depth.
Do I need fire bricks?: Yes for a wood fire you will use often: ordinary clay bricks and concrete blocks crack and spall with heat, fire bricks (refractory) do not. The usual build is an outer ring of face brick or block with an inner ring of fire brick laid with refractory mortar, and a steel ring insert is the alternative.
Mortar or dry stack?: Dry-stacked rings work for tapered blocks and for a low pit; brick rings are better mortared, with refractory mortar on the fire-brick liner and ordinary mortar outside. Leave two or three unmortared vertical joints in the bottom course for air. Never seal a fire pit; trapped water turns to steam and breaks the bricks.

How many bricks per square metre (and per square foot)?
Bricks and blocks per square metre and per square foot for the common formats, how the mortar joint changes the count, and what to order for a 10 m² wall.
How many bricks per square foot? Walls, patios and floors
Modular bricks per square foot of wall (about 7) and laid flat on a patio (4.5 to 5), bricks for 100 to 500 sq ft with 5% waste, mortar, and the UK brick per sq ft.
How many blocks for a retaining wall? (12x4, 16x6 and 18x8 in)
Retaining wall blocks for 10 to 50 ft walls at 1, 2 and 3 ft high in the three common sizes, plus the gravel base and the drainage stone behind the wall, and metric.
How many bags of mortar per 100 bricks (and per 100 blocks)?
80 lb and 60 lb mortar bags per 100, 500 and 1,000 bricks or 8x8x16 blocks from the label yields, mortar volume per square metre of wall, and 25 kg bags for UK bricks.

Last updated 2026-09-12. Figures are planning estimates from typical product data: check the yield, size or coverage printed on what you buy and round up.