Potting Mix Volume Calculator
Calculate the volume of potting mix needed to fill containers, pots, or raised beds of various shapes.
Typically 85–95% to allow watering space at the top.
Formulas Used
Cylinder (Round Pot):
V = π × r² × h | r = diameter ÷ 2
Rectangle / Raised Bed:
V = length × width × depth
Square Pot:
V = side² × depth
Tapered / Cone (Frustum):
V = (π × h ÷ 3) × (R² + R·r + r²) | R = top radius, r = bottom radius
Adjusted Volume:
Vtotal = V × (fill% ÷ 100) × number of containers
Unit Conversions:
1 gallon = 231 in³ | 1 quart = 57.75 in³ | 1 ft³ = 1,728 in³ | 1 liter = 61.0237 in³
Assumptions & References
- Containers are assumed to have uniform cross-sections (cylinder, rectangle, square) or a linear taper (frustum/cone).
- A fill percentage of 85–95% is recommended to leave headspace for watering without overflow.
- Bag sizes are estimates; actual bag volumes may vary slightly by brand. Always round up to avoid running short.
- Potting mix volume is measured loose/uncompressed. Settling after watering may reduce volume by 5–10%.
- Frustum formula source: standard solid geometry — V = (πh/3)(R² + Rr + r²).
- Unit conversions per USDA and standard US customary measurements.