Mulch Calculator
Estimate bulk cubic yards or bag count from bed area and mulch depth without assuming one universal bag size.
Continue your project estimate
Plan topsoil for the same bed →How the mulch calculation works
Convert your mulch depth from inches to feet, multiply by the bed area to get cubic feet, then divide by 27 for cubic yards.
cubic yards = area (ft²) × depth (ft) ÷ 27
For bags, the calculator divides the waste-adjusted cubic feet by the bag volume printed on the product label and rounds up to a whole bag.
Example
A 20 ft × 10 ft bed at 3 in deep is 50 ft³, or about 1.85 yd³ before extra material. With 5% extra, that becomes about 52.5 ft³ or 1.94 yd³.
Why we do not assume a bag size
Mulch bag volume varies by product and retailer. Enter the cubic-foot volume printed on the exact bag you plan to buy. This avoids false precision and makes the result useful across brands.
Before buying mulch
Confirm whether you are ordering bulk material or bags. For bags, use the exact cubic-foot volume printed on the product rather than a generic bag size. For bulk orders, ask the supplier how they sell and round quantities so the calculator output can be matched to a real order.
Related calculators
500-sq-ft mulch example · Topsoil Calculator · Gravel Calculator
Bagged and bulk mulch use different purchase units
The same bed area and depth can be purchased as bulk cubic yards or as bags with a stated cubic-foot volume. Convert the project volume first, then apply the package size or supplier unit that matches the way you will actually buy the material.
Depth should reflect the project goal and site condition rather than a hidden default. Existing mulch, plant crowns, tree trunks and sloped areas can affect the practical amount spread on site, so use the calculated volume as a planning quantity and compare it with the final bed preparation.
How mulch depth changes whole-bag purchases
A 20 × 12 ft planting bed measures 240 sq ft. At a hypothetical 2-inch replenishment depth, the volume is 240 × (2 ÷ 12) = 40 cubic feet. If your actual product contains 2 cubic feet per bag, that is 20 whole bags. Changing only the planned depth to 3 inches gives 60 cubic feet, or 30 bags of that same product, before any additional allowance.
Use only the incremental depth required for a top-up, not the thickness of the existing plus new layer. Confirm suitable application depth, drainage and clearance around plants or tree trunks separately; changing the depth in the calculator is a quantity scenario rather than horticultural advice.