Mulch & Soil Calculator
Cubic yards, bags, and bales of mulch, topsoil, or compost for any bed
How to Calculate Mulch
Mulch is sold by the cubic yard in bulk and by the cubic foot in bags. Multiply the bed's area in square feet by the depth in inches, divide by 12 to get cubic feet, then divide by 27 to get cubic yards. For round beds, the area is Ο Γ radiusΒ²; for triangles, it's base Γ height Γ· 2. The calculator lets you add as many beds as you need and totals them for you.
A quick shortcut: one cubic yard covers 324 square feet at 1 inch deep. Divide 324 by your depth to see how far a yard goes β 162 sq ft at 2 inches, 108 at 3 inches, 81 at 4 inches.
Worked Example: A 20 Γ 4 ft Bed
A 20 Γ 4 ft bed is 80 sq ft. At 3 inches deep that's 80 Γ 3 Γ· 12 = 20 cubic feet, or about 0.74 cubic yards. That's 10 bags of 2 cu ft mulch β or 7 bags of 3 cu ft. Add about 10% extra, since fresh mulch settles and beds are rarely perfectly measured.
How Much a Bag of Mulch Covers
How Deep Should Mulch Be?
For most garden beds, 2β3 inches is the sweet spot: deep enough to block weeds and hold moisture, shallow enough to let water and air through. Fine mulches can go thinner; coarse nuggets can go a little deeper. Around trees, spread mulch in a wide ring but keep it a few inches away from the trunk β piling it up against the bark ("mulch volcanoes") invites rot and pests. Refresh beds with about an inch each year rather than piling on a full new layer.
Frequently Asked Questions
- How many bags of mulch are in a cubic yard?A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cu ft mulch or 9 bags of 3 cu ft mulch to equal one cubic yard.
- How much area does a yard of mulch cover?One cubic yard covers about 324 square feet at 1 inch deep, 162 square feet at 2 inches, 108 square feet at 3 inches, and 81 square feet at 4 inches.
- How deep should I put mulch?2 to 3 inches is ideal for most garden beds. Use about 1.5 to 2 inches for rubber mulch, and keep any mulch a few inches away from plant stems and tree trunks.
- Is it cheaper to buy mulch in bags or bulk?Bags are convenient for small beds. Once you need more than about 2 cubic yards (27 bags of 2 cu ft), bulk mulch delivered is usually cheaper even after the delivery fee, and saves you dozens of trips with bags.
- How many bales of pine straw do I need?A standard bale of pine straw covers roughly 40 to 50 square feet at about 3 inches deep. Divide your total bed area by 50 and round up, adding a bale or two for touch-ups.
- How often should mulch be replaced?Organic mulch breaks down over time. Most beds need a top-up of about 1 inch each year, and a fuller refresh every 2 to 3 years. Rubber mulch and stone don't decompose and rarely need replacing.
Results are estimates for planning and budgeting. Weights and coverage vary by supplier, moisture, and product β confirm with your supplier before ordering.