How to Calculate Mulch Quantity
Bed area × depth, converted to cubic yards or bags
Area times depth
Measure the bed's area (length × width for a rectangular bed, or break an irregular bed into sections), then multiply by the desired mulch depth. A depth of 2-3 inches is typical for most mulch applications — deeper than that can suffocate plant roots, shallower doesn't suppress weeds as effectively.
Converting to cubic yards
Convert your depth to feet (2 in = 0.167 ft) and multiply by area in square feet to get cubic feet, then divide by 27 to get cubic yards — bulk mulch is typically sold and delivered by the cubic yard.
Or convert to bags
Bagged mulch is commonly sold in 2 cubic foot bags. Divide your total cubic feet by 2 to get the number of bags needed — useful for smaller beds where a bulk delivery isn't practical.
Worked Example
A 200 ft² bed, 3 inches deep.
Depth in feet: 3 ÷ 12 = 0.25 ft
Volume: 200 × 0.25 = 50 ft³
Cubic yards: 50 ÷ 27 ≈ 1.85 yd³
Or in bags (2 ft³ each): 50 ÷ 2 = 25 bags
Related Calculators
Related Guides
Sources
NIST SP 811
Unit conversion reference (cubic feet, cubic yards, cubic metres).
NIST SP 811 — reference