1. Draw the footprint
Mark each rectangle, circular landing, and section whose area is already known. Measure to the edges that will contain gravel. Do not multiply overlapping shapes twice. In GravelSum, add one region for each non-overlapping piece.
2. Use one depth or split the project
The calculator applies the shared layer depth to every region unless you enter a depth override on that region. If a 120 ft² patio uses 2 in while a 40 ft² border uses 3 in, enter the common value once and override the section that differs.
3. Work the volume
For a 12 ft × 10 ft patio at 2 in loose placed depth:
120 ft² × (2 ÷ 12) ft = 20 ft³
20 ft³ ÷ 27 = 0.7407 yd³
A separate circular sitting area 8 ft across has area π × 4² = 50.265 ft². At the same 2 in depth it adds 8.378 ft³, bringing the combined volume to 28.378 ft³, or 1.051 yd³.
4. Compare the way stores sell it
For bags sold by volume, divide needed volume by volume per bag and round up to a whole bag. If the example above uses 0.5 ft³ bags, 28.378 ÷ 0.5 = 56.756, so the order is 57 bags before any separate allowance. A bag price is not needed to calculate this quantity.
For bags sold by weight, use the supplier’s loose bulk density range. The bag count may also be a range. Keep it that way until the supplier provides a tighter product figure. If the supplier quotes this pea gravel by short ton or metric tonne, use the cubic-yards-to-tons converter with that product’s density and quoted unit.
Pea gravel can travel beyond its intended area, so use appropriate containment; Fox Landscape Supply’s installation notes likewise call for a border.