Stone calculator
Firepit Stone Calculator
Enter the finished diameter and block size to get blocks per course, total blocks, base gravel and liner requirements.
Your project
36-48 inches outside is the comfortable range for a backyard pit.
12-14 inches above grade is standard for seating-height warmth.
Blocks needed
30
10 per course × 3 courses
- Inside diameter (usable fire area)
- 31"
- Courses
- 3
- Base gravel (4" compacted)
- 4.22 cu ft
- Fire brick (split, 4.5" × 2.5")
- 100 bricks
- Construction adhesive
- 2 tubes
- Estimated block cost
- $120
Never build a fire pit on a wood deck, under a tree canopy, or within 10 feet of a structure. Check local burn ordinances — many suburbs regulate pit size and setback.
The shareable link reopens this calculator with your exact inputs.
Sizing a fire pit
A 36-44 inch outside diameter with a 12-14 inch wall is the standard backyard pit: big enough for a real fire, small enough that people sitting 3 feet back still feel the heat. Inside diameter should end up around 24-30 inches.
Blocks per course is the inside circumference divided by the block face length. Because the blocks form a ring, use the mean diameter — outside diameter minus one block width — for the circumference, or you will over-order.
Fire brick and heat
Wall block and natural stone are not rated for direct flame contact. Repeated heating drives moisture out of concrete block, which spalls and eventually cracks. A split fire brick liner set with refractory mortar absorbs that and can be replaced.
Leave the base as compacted gravel or sand rather than solid concrete: trapped moisture under a fire turns to steam, and steam in a sealed slab cracks it.
Blocks per course by pit size
Using 12 inch face-length wall block.
| Outside diameter | Blocks per course | 3 courses (12") |
|---|---|---|
| 36" | 8 | 24 |
| 40" | 9 | 27 |
| 44" | 10 | 30 |
| 48" | 11 | 33 |
| 54" | 13 | 39 |
Frequently asked questions
+How many blocks do I need for a fire pit?
A 44 inch pit with 12 inch blocks takes about 10 blocks per course, so 30 blocks for a 12 inch wall in three courses.
+How big should a fire pit be?
36-44 inches outside diameter, 24-30 inches inside, and 12-14 inches tall. Larger pits look impressive and radiate heat past where people actually sit.
+Do I need fire brick in a fire pit?
For regular wood fires, yes. Standard concrete wall block spalls under direct flame within a season or two. Gas fire pits do not need a liner.
+What goes in the bottom of a fire pit?
Four inches of compacted gravel or coarse sand for drainage. Never a sealed concrete pad, which traps moisture and cracks.