Cinder Block Fire Pit Calculator
Count blocks for a round fire pit.
Your result
Enter your numbers and press the button. Your result appears here.
Laid in a ring, each block covers its length along the centre line of the wall.
How it works
Blocks per course = π × (inside diameter + block depth) ÷ block length, rounded up.
Example: a 36 in fire pit with 8 in deep blocks takes 9 blocks per course, 27 for 3 courses.
At a glance
Same settings as the calculator above, changing only the courses.
| Courses | Blocks | Height |
|---|---|---|
| 2 | 18 | 16 in |
| 3 | 27 | 24 in |
| 4 | 36 | 32 in |
Standard block sizes
| Nominal | Actual | Blocks per 100 ft² of wall |
|---|---|---|
| 4×8×16 | 3⅝ × 7⅝ × 15⅝ in | 112.5 |
| 6×8×16 | 5⅝ × 7⅝ × 15⅝ in | 112.5 |
| 8×8×16 | 7⅝ × 7⅝ × 15⅝ in | 112.5 |
| 12×8×16 | 11⅝ × 7⅝ × 15⅝ in | 112.5 |
Nominal sizes include a ⅜ in mortar joint.
Common questions
How many blocks per square foot?
A standard block with an 8×16 in face covers 1.125 blocks per square foot, or 112.5 blocks per 100 square feet.
Can I use regular concrete blocks for a fire pit?
Ordinary blocks can crack or spall with direct heat. Many builders line the inside with fire brick.