How this calculator works
It multiplies the bed area by the depth to get the volume of mulch, adds a small allowance for settling, and rounds up to whole bags or to whole cubic yards (cubic metres in metric) for a bulk order.
Bag counts use the bag volume printed on the bag, 2 cubic feet by default (60 litres in metric). One cubic yard is 27 cubic feet, the same as 13.5 two-cubic-foot bags.
area = length × width
cu ft = area × depth (in) ÷ 12
bags = cu ft × (1 + settling) ÷ cu ft per bag
bulk cu yd = cu ft × (1 + settling) ÷ 27Worked example
A 20′ × 10′ bed is 200 sq ft. At 3″ deep that is 200 × 3 ÷ 12 = 50 cu ft, or 1.85 cu yd. With 5% for settling it is 52.5 cu ft, which is 27 bags of 2 cu ft, or 2 cu yd if you order bulk.
Tips before you buy
- Measure odd-shaped beds as a few rectangles and add the results; it is close enough for mulch.
- Keep mulch 2–3″ away from tree trunks and house siding to avoid rot and pests.
- Topping up an existing bed usually needs only 1″ of fresh mulch, not the full depth.
- Past about one cubic yard, ask for a bulk price; delivery fees vary, so compare against the bag count.
Questions
- How deep should mulch be?
- Two to three inches (5–7.5 cm) suits most flower beds and shrub borders. Thinner layers let weeds through; much deeper layers can starve roots of air and keep the soil too wet.
- How many bags of mulch are in a cubic yard?
- A cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cubic feet or 9 bags of 3 cubic feet. In metric, one cubic metre is 1,000 litres, about 17 bags of 60 litres.
- Should I buy bags or bulk?
- Bags are easier to carry and store for small beds. For larger jobs bulk mulch is usually cheaper per cubic yard, but it is sold in whole or half yards and often has a delivery fee, so compare both totals.
- Why add extra for settling?
- Fresh mulch is fluffy and settles after watering and the first rain. A small allowance keeps the finished layer at the depth you planned.