Work out exactly how much mulch your garden beds need. Enter length, width and depth to get cubic yards, cubic feet and bag counts instantly.
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Enter the length and width of your bed in feet and the mulch depth you want in inches. The calculator converts depth to feet, multiplies the three dimensions to get cubic feet, divides by 27 for cubic yards (the unit bulk suppliers use), and divides the cubic feet by your chosen bag size, rounding up to whole bags. Cubic yards suit bulk delivery orders; the bag count suits a store run. Add about 10 percent extra if your beds have irregular edges or slopes, since mulch settles and shifts in its first season.
Mulch is sold by volume, so the math is area times depth. The calculator multiplies bed length by bed width (both in feet) by depth converted from inches to feet (depth / 12) to get cubic feet. It then divides by 27 to get cubic yards, because one cubic yard equals 27 cubic feet and bulk suppliers price by the yard. Finally it divides cubic feet by your selected bag size and rounds up to whole bags, since stores do not sell fractions of a bag.
Measure the longest length and widest width of each bed with a tape measure, in feet. If your bed is irregular, break it into rectangles, calculate each one, and add the areas together, or use the circular-bed rule (3.14 × radius²⁾ and enter the total area mentally. Enter the numbers above, pick the mulch depth you want in inches, and choose the bag size your store sells (1.5, 2, or 3 cubic feet). This mulch estimator updates instantly: cubic feet and cubic yards for bulk ordering, plus the bag count for a store run.
Depth matters more than most people think. For flower beds, 2 to 3 inches is the sweet spot: enough to block weeds and hold soil moisture without smothering shallow roots. Around trees and shrubs, go 3 to 4 inches, but keep the mulch pulled several inches back from the trunk in a donut shape. Never pile mulch against a trunk or stem, the so-called mulch volcano, because trapped moisture causes rot and invites pests. Use only 1 to 2 inches when refreshing an already mulched bed, and never go deeper than 4 inches in planted beds. Here is a quick mulch coverage chart for one cubic yard: 162 square feet at 2 inches, 108 at 3 inches, 81 at 4 inches.
For small jobs under about one cubic yard, bagged mulch wins on convenience: no delivery fee, easy car transport, and you buy exactly the number of bags the calculator gives you. Above one to two cubic yards, bulk mulch delivered by the truckload is almost always cheaper per cubic foot, often $30 to $45 per yard versus $54 or more for the equivalent in bags. Remember that one cubic yard equals 13.5 two-cubic-foot bags (18 of the 1.5 cu ft bags, 9 of the 3 cu ft bags), so bag costs add up fast on large beds. Spring multi-bag sales can flip the math back toward bags, so compare your local prices before you order.
Compare the total cost of bagged mulch and bulk mulch before you order: at typical prices a two-yard job runs about $60 to $90 in bulk versus $100 or more in bags, before the delivery fee, so bulk almost always wins once you pass the one-yard mark.
Take a flower bed 20 feet long and 10 feet wide, and you want 3 inches of bark mulch. First convert depth: 3 / 12 = 0.25 feet. Volume in cubic feet: 20 × 10 × 0.25 = 50 cubic feet. In cubic yards: 50 / 27 = 1.85 yards, so order 2 yards of bulk mulch to be safe. In bags: 50 / 2 = 25 two-cubic-foot bags, or ceil(50 / 3) = 17 three-cubic-foot bags. That is the same math the calculator above runs for any bed size.
Spread mulch 2 to 4 inches deep. Three inches is the sweet spot for most flower beds: it suppresses weeds and holds moisture without starving roots of oxygen. Around trees and shrubs you can go 3 to 4 inches, and a 1 to 2 inch layer is enough when refreshing existing mulch. Never exceed 4 inches in planted beds.
One cubic yard equals 27 cubic feet. That works out to 13.5 two-cubic-foot bags, 18 one-and-a-half-cubic-foot bags, or 9 three-cubic-foot bags. Since you cannot buy half a bag, always round up: a job needing 13.5 bags means buying 14.
At the recommended 3-inch depth, 100 square feet needs about 0.93 cubic yards, which is 25 cubic feet, or 13 two-cubic-foot bags. At 2 inches deep you need about 0.62 yards, roughly 9 bags. Measure your exact bed and use the calculator above for your depth.
Bulk is usually much cheaper per cubic foot. At typical prices, a cubic yard costs about $54 in 2 cu ft bags versus $30 to $45 in bulk. Bags win for small jobs under a yard, since there is no delivery fee and they are easier to haul. For jobs over 1 to 2 yards, bulk delivery usually saves real money.
Organic mulch like bark and wood chips decomposes and settles about 10 to 20 percent in its first season, so top-dress beds with 1 to 2 inches every spring to keep color and depth. Plan a full refresh or partial removal every 2 to 3 years as old material breaks down and compacts.
One 2 cubic foot bag covers about 12 square feet at 2 inches deep, 8 square feet at 3 inches, and 6 square feet at 4 inches. A 3 cu ft bag covers 18, 12, and 9 square feet at those same depths.
No. Piling mulch against a tree trunk, called volcano mulching, traps moisture against the bark and invites rot, fungi, and pests. Keep mulch pulled back several inches from trunks and stems in a flat donut shape instead of a mound.
Break an irregular bed into rectangles or circles, calculate each area, and add them together. For a circular bed, use 3.14 times the radius squared for the area in square feet. Then multiply total area by depth in inches divided by 12 to get cubic feet, and divide by 27 for cubic yards.
Spring, after the soil has warmed, is the best time to mulch flower beds: the layer locks in spring moisture and smothers weeds before summer heat arrives. Top up the depth again in fall if winter winds thin it out, and avoid spreading mulch on frozen ground, where it can trap frost against shallow roots.