Mulch Calculator: Cubic Yards for Garden Beds
Free mulch calculator to estimate cubic yards for a rectangular garden bed using length, width and mulch depth.
How to calculate mulch volume
Measure the garden bed length and width in feet and choose a depth in inches. Multiply length by width by depth in feet, then divide the cubic feet by 27 to convert to cubic yards.
Example estimate
A 20 by 6 foot bed covered with 3 inches of mulch needs 30 cubic feet, or approximately 1.11 cubic yards before any extra allowance.
Before you buy materials
Avoid piling mulch against tree trunks or plant stems. Appropriate depth depends on your mulch type, soil and plants. All results are planning estimates, not professional construction advice.
Measure beds and depth
Measure each rectangular bed in feet. Convert mulch depth from inches to feet by dividing by 12. Multiply length × width × depth to find cubic feet, then divide by 27 to get cubic yards. Add separate beds together.
Example with a buying allowance
A 20 × 6 ft bed at 3 inches deep needs 30 cubic feet, or about 1.11 cubic yards. With 10% extra, allow approximately 1.3 cubic yards. Bulk suppliers may have their own order increments.
Common questions
What if my bed is curved?
Break it into smaller approximate rectangles, or measure its total surface area and multiply by depth.
Can I add new mulch over old mulch?
Measure existing depth first so the total layer does not become excessive.
Where should mulch go near a tree?
Keep mulch away from direct contact with the trunk and follow appropriate planting guidance.