Fire Pit Size & Gravel Calculator
Size a fire pit and its gravel base — pad volume, weight and the safe clearance you need around the flames.
How it works
Pad area = π × (pad diameter ÷ 2)² · Gravel volume = pad area × depth · Clear-space diameter = pit diameter + 2 × clearance
A gravel base keeps a fire pit level and drains water away from the fire, and it also acts as a non-combustible buffer between embers and the ground. Volume is the circular pad area times the base depth; crushed gravel weighs roughly 1.4 tons per cubic yard, so most home pits only need a fraction of a yard. For safety, keep at least 7 ft of clear space between the pit and any seating, wall or overhanging branches, and more if there is wind.
Worked example
A 5 ft gravel pad has an area of π × 2.5² = 19.6 sq ft. At 4 inches (0.33 ft) deep that is 6.5 cu ft, or 0.24 cu yd — about 0.34 tons. With a 3 ft pit and 7 ft clearance, the flames should have a clear circle 3 + 14 = 17 ft across.
Frequently asked questions
How deep should a fire pit gravel base be?
A 4–6 inch compacted gravel base is standard. Deeper bases give better drainage and stability on soft or clay soils; on firm, well-draining ground 4 inches is plenty.
How far should a fire pit be from the house?
Keep a wood-burning fire pit at least 10 ft — ideally more — from any structure, fence, or overhanging tree, and never use one under a covered porch or roof. Check local codes, which often set a specific minimum.
What kind of gravel goes under a fire pit?
Use crushed stone or pea gravel for the base and, if you want a decorative in-pit layer, lava rock or fire-rated gravel — never river rock or wet stones, which can trap steam and crack or pop when heated.
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This calculator is for educational purposes. Double-check important results before acting on them.