Free mulch quantity & purchase planner
How much mulch do you need—and is it cheaper by the bag or delivered? Measure your beds, allow for mulch already in place, and compare the quantities you can actually buy.
BiznTools · bizntools.com/home-projects/mulch-calculator
Enter bed measurements to calculate.
See the volume you need, the quantities to buy and the cost of each option.
Measuring outdoors? Download a blank supplier worksheet for bed measurements, bag options and supplier quotes.
Your measurements and prices stay in this tab.
The math, without the guesswork
Find the area of each bed in square feet. Multiply it by the depth of fresh mulch in inches, then divide by 12 for cubic feet. Add the beds together before applying any extra allowance. Divide by 27 for cubic yards, or by the volume on a bag. Round the purchase up only after you have the total.
For a rectangle, multiply length by width. For a triangle, use half the base times its perpendicular height. A circle uses π × radius²; a ring subtracts the clear center. Split irregular beds into non-overlapping shapes.
20 ft × 10 ft = 200 sq ftCheck what remains before adding a new layer. Subtract usable existing depth from your target. Multiply the area by those fresh inches and divide by 12.
200 × 3 ÷ 12 = 50 cu ftDivide by the bag volume and buy whole bags. For bulk, apply the supplier’s minimum and increment. Compare the price of this rounded purchase, including the delivery you enter.
50 ÷ 2 = 25 bagsA quick reference
These figures are area and depth conversions, before extra allowance. A yard means a cubic yard of material, not a square yard of bed.
| Fresh depth | 1 cubic yard | 1 bag, 2 cu ft | 1 bag, 3 cu ft |
|---|---|---|---|
| 1 in | 324 sq ft | 24 sq ft | 36 sq ft |
| 2 in | 162 sq ft | 12 sq ft | 18 sq ft |
| 3 in | 108 sq ft | 8 sq ft | 12 sq ft |
| 4 in | 81 sq ft | 6 sq ft | 9 sq ft |
For one cubic yard, buy 18 bags of 1.5 cubic feet, 14 bags of 2 cubic feet, or 9 bags of 3 cubic feet. The 14 two-foot bags contain 28 cubic feet—one cubic foot more than a yard. For your whole project, use the calculator’s pooled total rather than rounding every yard separately.
A 1.5-cu-ft bag covers 6 square feet at three inches. A 2-cu-ft bag covers 8; a 3-cu-ft bag covers 12. Use the volume actually printed on the bag.
From garden plan to supply yard
Use the blank mulch supplier worksheet (PDF) to record each bed’s area and fresh layer, compare 1.5, 2 and 3 cu ft bags, and collect complete supplier quotes. Once you have entered your measurements above, Download order PDF fills in the quantities for you.
Compare the same type of mulch. Check the bag’s printed volume and the supplier’s minimum, order increment and delivery charge. The fewest bags may not be the cheapest purchase, and a lower price per yard can be outweighed by delivery.
From measurement to purchase
The bed is 200 square feet. With no old mulch and no extra allowance, 200 × 3 ÷ 12 gives 50 cubic feet, or 1.852 cubic yards. Buy 25 two-cubic-foot bags. If your supplier sells in quarter-yard increments, order 2 cubic yards.
For that same bed, 25 bags at $4 each cost $100. Two cubic yards at $40 per yard cost $80 before delivery. A $30 delivery fee makes the bulk total $110, so bags cost $10 less. Without that fee, bulk costs $20 less. Use your actual quotes.
A 200-square-foot bed already has two inches of usable mulch. To reach a total depth of three inches, add only one inch: 200 ÷ 12 = 16.667 cubic feet. That is nine two-cubic-foot bags after rounding. If the existing layer already meets the target, no fresh mulch is calculated.
Measure what is already there
Push the mulch aside in several spots and measure the usable layer. A three-inch target over two inches of existing mulch needs one inch of fresh material, not another full three inches.
Penn State Extension describes two to four inches for landscape trees, with less on poorly drained soil and one to two inches for fine or double-shredded material. It advises keeping the trunk and root flare clear. Match the depth to your actual material and site.
For a tree ring, enter the clear center’s diameter so that area is excluded. The sketch is a measurement aid, not a planting specification.
Before you order
A cubic yard is 27 cubic feet. That equals 13.5 two-cubic-foot bags, so you need 14 whole bags to cover at least one yard. It equals exactly nine three-cubic-foot bags or 18 bags of 1.5 cubic feet. For several beds, add their volumes first so each small bed does not create a separate rounded-up bag.
One cubic yard covers 324 square feet at one inch, 162 square feet at two inches, or 108 square feet at three inches. Coverage changes with depth. These geometric figures exclude any extra allowance and do not choose an appropriate layer for your plants.
Enter the target total layer and the usable depth already there. The calculator subtracts the existing layer. For a three-inch target over two inches of usable mulch, it adds one inch. If you have already measured the fresh top-up alone, use that as the target and set existing depth to zero.
No. Compare the full order: whole bags and any pickup charge versus the supplier’s rounded bulk quantity and delivery. Minimum orders can matter on small projects. Enter both prices to see the difference; a blank price is never treated as a free product.
For a circle, measure the diameter across its center. For a ring, enter the outer diameter and the diameter of the clear center. Both must use feet. The clear center is excluded from the area. Keep mulch away from the trunk and the root flare; a quantity estimate does not decide the correct clearance.
Use guidance for your plants, material and drainage. Penn State Extension describes two to four inches for landscape trees, less on poorly drained soil, and one to two inches for finely textured or double-shredded mulch. It also advises checking the old layer before adding more and keeping the root flare visible. The initial three inches here is an editable example, not a prescription.
It compares material purchases plus the pickup or delivery charges you enter. Add local tax and installation separately using the supplier’s quote. Mulch weight varies with material and moisture; volume alone does not establish a safe vehicle load.
Penn State Extension — Mulching Landscape Trees — Depth, drainage, existing layers and keeping mulch away from the trunk. This guidance informs the explanation; the tool does not select a safe depth.
University of Minnesota Extension — Mulching for soil and garden health — Material selection and applying mulch without restricting soil aeration.