Calculator inputs
Example data table
| Scenario | Shape | People | Fuel | Suggested opening | Safety clearance | Notes |
|---|---|---|---|---|---|---|
| Small patio chat | Round | 4 | Gas | ~2.0 ft inner diameter | ~3.0 ft | Compact footprint and easier temperature control. |
| Family evening | Round | 6 | Wood | ~2.6 ft inner diameter | ~3.5 ft | More room for logs and comfortable spacing. |
| Bench seating | Rectangle | 8 | Gas | ~2.0 × 4.0 ft opening | ~3.0 ft | Good for linear seating and conversation lines. |
Formula used
- Perimeter target: Perimeter = People × ArcAllowance × IntensityFactor
- Round opening: Diameter = Perimeter ÷ π
- Square opening: Side = Perimeter ÷ 4
- Rectangle opening: Width = Perimeter ÷ (2 × (1 + Ratio)), Length = Ratio × Width
- Outer size: Outer = Inner + 2 × WallThickness
- Footprint size: Footprint = Outer + 2 × SafetyClearance
- Volume: OpeningVolume = OpeningArea × FireDepth
How to use this calculator
- Select your measurement system and preferred fire pit shape.
- Enter how many people you want to seat comfortably.
- Set seating distance and a safety clearance around the pit.
- Adjust wall thickness and depth to match your build style.
- Press Calculate to see dimensions, footprint, and volume.
- Download CSV or PDF to share with your installer.
Planning guidance
Seating capacity and comfortable perimeter
Fire pit sizing starts with the space each person needs at the rim. The calculator assigns a perimeter allowance per person and scales it by burn intensity. More perimeter reduces crowding, improves sightlines, and keeps chairs evenly spaced. Wood typically needs a slightly larger allowance to accommodate logs, sparks, and tending. Gas can be tighter because heat and flame are more controllable.
Shape selection for real outdoor layouts
Round pits support conversation because everyone faces the center at similar angles. Square pits maximize opening area on small patios but require careful corner clearance. Rectangles suit benches or long sectional seating. The aspect ratio converts the same perimeter into a linear footprint, which helps when patio depth is limited and you want longer flame presentation.
Clearance, footprint, and reserved space
Good planning considers more than the opening. The calculator reports inner opening, outer wall, and a safety clearance zone. Footprint values help keep furniture, planters, and planting beds away from heat. Reserved space adds your seating distance beyond the outer edge so you can confirm chairs and walkways still fit without tight circulation.
Depth and volume for materials planning
Depth affects capacity and base stability. Opening volume is calculated from opening area and depth, helping you compare designs and estimate fill. For gas pits, media depth estimates how much lava rock or glass is needed to cover the burner area. In imperial units, the tool also estimates typical 20 lb media bags for purchasing.
Practical checks before construction
Use results as a planning baseline, then confirm the final build with the product manual and local requirements. Verify distances to fences, structures, and overhead elements, and ensure airflow is not blocked by walls or dense planting. Choose a non-combustible base, plan drainage, and increase clearance for windy sites. For comfort, aim for a level pad, stable seating, and low-glare lighting. Keep a metal lid or extinguisher nearby, and store extra fuel away from the cleared zone always.
FAQs
1) What seating distance should I use?
Start with 24–30 inches (or 60–75 cm) for warmth and comfort. Increase the distance for taller flames, windy sites, or if children will be present. The reserve-space output helps confirm your patio still has clear walkways.
2) Why does wood often require a larger opening?
Wood fires need room for log placement, tending tools, and stronger airflow. A larger opening also helps distribute heat across the seating ring and reduces crowding around the rim during active burning.
3) How do I choose between round and rectangular?
Pick round for balanced conversation and a compact footprint. Pick rectangular when you have bench seating, a long wall, or a narrow patio. Aspect ratio lets you match the pit to your available layout.
4) Is the safety clearance the same as local code?
No. Clearance values here support planning only. Always follow the appliance manufacturer’s minimum clearances and any local rules. If guidance conflicts, use the most conservative requirement for safer spacing.
5) What does “opening volume” tell me?
Opening volume estimates the usable cavity inside the pit. It helps compare designs and approximate media or fuel capacity. It does not replace burner specifications or heat output ratings for gas units.
6) Can I use this for in-ground fire pits?
Yes, as a sizing starting point. Ensure soil stability, drainage, and non-combustible lining. In-ground builds may need larger clearances and additional venting or gravel layers depending on the design.