How many fire bricks do I need for a fire pit?

For a circular fire pit, divide the circumference by the brick width plus mortar joint. A 1m diameter pit has a circumference of 3.14m — with 65mm bricks and 10mm joints, that's about 42 bricks per course. With 4 courses high, you need approximately 168 fire bricks. Add 10% for cuts.

What type of brick should I use for a fire pit?

Use fire bricks (refractory bricks) for the inner ring as they withstand temperatures up to 1,300°C. Standard bricks will crack and spall from heat cycling. Fire bricks are typically 230mm × 114mm × 65mm. For the outer decorative ring, standard engineering bricks or natural stone are fine as they don't contact flames directly.

Does a fire pit need drainage?

Yes, fire pits need drainage to prevent rainwater pooling in the base. Lay 100-150mm of clean gravel (20mm pea shingle) in the base before use. Don't use concrete for the base — it can crack from heat and trap water. Some builders also install a 50mm drain pipe through the base for complete drainage.

What mortar do I use for a fire pit?

Use fire cement or refractory mortar for the inner ring of fire bricks — standard mortar will crack at high temperatures. For the outer ring (if using standard bricks), normal mortar is fine. Fire cement is available in tubs from builders' merchants. Apply in thin joints (5-10mm) between fire bricks.

Do I need planning permission for a fire pit?

A permanent fire pit structure doesn't usually need planning permission if it's in your garden and is a reasonable size. However, check with your local council about smoke control zones — in a Smoke Control Area, you can only burn authorised fuels. Keep the fire pit at least 2m from boundaries and any flammable structures. Be considerate of neighbours.

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Fire Pit Calculator — Fire Bricks, Mortar & Cap Stones

Calculate fire bricks, mortar, cap stones and drainage gravel for a garden fire pit.

Inside Diameter

Pit Shape

Wall Courses

4 courses = ~300mm high

Fire Brick Price

Cap Stone Price

Gravel Price

How We Calculate This

This calculator determines the fire bricks, mortar, cap stones and drainage gravel needed for a garden fire pit.

Brick count

Circular: Bricks per Course = Circumference / (Brick Width + Joint)
Square: Bricks per Course = Perimeter / (Brick Width + Joint)
Total Bricks = Bricks per Course x Number of Courses

Drainage and capping

Gravel drainage in the base at 100mm depth. Cap stones along the top edge at approximately 300mm centres for a finished look and seating edge.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.