Mulch calculator

How mulch is calculated

Mulch is sold by the cubic yard in bulk and by the cubic foot in bags, so the calculator works out the volume of the bed at your depth and reports it both ways. Weight is there for loading a truck or trailer, and cost appears once you enter a price per yard.

If you add an allowance, it multiplies the volume before the bags, tons and cost are worked out. For mulch it normally stays at 0.

Worked example: 20 × 10 ft bed, 3 in deep

The calculator opens on a 20 × 10 ft bed with 3 in of shredded hardwood mulch, bought in 2 ft³ bags.

1. Area: 20 × 10 = 200 ft².
2. Volume: 200 × 3 ÷ 12 = 50.0 ft³.
3. Cubic yards: 50.0 ÷ 27 = 1.85 yd³. A bulk yard sells by the half or whole yard, so order 2 yd³.
4. Bags: 50.0 ÷ 2 = 25 bags of 2 ft³. In 3 ft³ bags it is 50.0 ÷ 3 = 16.67, rounded up to 17.
5. Weight: 1.85 × 600 ÷ 2,000 = 0.56 tons, about 1,111 lb.

How deep to spread mulch

For new beds, 2–3 in is the working range, and 3 in is deep enough to shade out most weed seedlings. Deeper is not better: more than 4 in can smother roots and keep the soil too wet, and the calculator warns when you enter more. If last year's mulch is still there, a 1–2 in top-up is usually all a bed needs, so measure what is left before you order.

• Measure each bed and enter it with “+ Add another bed”; each bed keeps its own depth, and the yards and bags are totalled for the whole job. A long strip along a fence is just a narrow rectangle.
• For a ring around a tree, use the circle shape and the ring's diameter, then pull the mulch back from the trunk when you spread it.
• Island beds with curved edges are close enough as a circle or a rectangle of the same rough area.

Bags or bulk

Bags are easy to carry and store, but they get expensive fast. A cubic yard is 13.5 two-cubic-foot bags or 9 three-cubic-foot bags, and the calculator notes when a bag count climbs past a sensible number. To find the break-even, divide the bulk price per yard by the number of bags in a yard. At $35 a yard, a 2 ft³ bag has to cost $2.59 or less to match bulk, before the delivery fee.

Hardwood or bark

The two choices in the calculator differ mostly in weight and texture, not in how much you need: the volume for a bed is the same whichever you pick. Shredded hardwood is the common bulk product, and its stringy pieces knit into a mat. Bark nuggets are chunkier and, at about 500 lb a yard against roughly 600 lb for hardwood, the lighter of the two; pine bark is the lightest of all. Both weigh more when they arrive wet, so treat the weight line as a guide for loading rather than a scale ticket.

Mulch is light for its bulk: a yard of hardwood mulch is about 600 lb and bark nuggets about 500 lb, so a pickup bed fills up before it reaches its payload. As a rule of thumb a half-ton pickup carries about 1 yd³ of mulch per trip.