Mulch Calculator
Mulch is sold two ways: in 2-cubic-foot bags from the garden center or by the cubic yard from a bulk supplier. The trick is knowing which is cheaper for your job, and that comes down to how much you actually need. Enter your bed dimensions and the depth you want below. You'll get bags, cubic yards, and a cost estimate, so you can see at a glance whether to grab bags or order a bulk drop.
How much mulch you need, bags or a bulk drop
Mulch comes two ways: 2-cubic-foot bags from the garden center, or by the cubic yard dumped from a bulk supplier. The volume you need is the same either way; the smart move is knowing which is cheaper for your beds. Enter the bed size and the depth you want and the calculator returns bags, cubic yards, and a cost, so the call is obvious before you load the car.
The math, and the one number worth memorizing
Multiply bed length by width for square footage, multiply by depth in feet for cubic feet, then divide by 27 for yards or by 2 for standard bags. The shortcut to keep in your head: one cubic yard covers 100 square feet at 3 inches deep. Everything scales from there. Mulch settles and breaks down over a season, so order about 10 percent over your flat number.
How far a cubic yard of mulch goes
One yard is 27 cubic feet, which spreads differently depending on depth. This is the table that answers "how many bags do I need" without the guesswork.
| Depth | 1 cubic yard covers | 2 cu-ft bags per 100 sq ft |
|---|---|---|
| 1 inch | ~324 sq ft | ~4 bags |
| 2 inches | ~162 sq ft | ~9 bags |
| 3 inches | ~108 sq ft | ~13 bags |
| 4 inches | ~81 sq ft | ~17 bags |
A cubic yard equals 13.5 of the standard 2-cubic-foot bags, which is why bulk gets cheaper fast once a job runs past a dozen bags.
How deep, by bed type
| Where | Depth | Why |
|---|---|---|
| Established beds | 2-3 in | Holds moisture and blocks weeds without smothering roots |
| New beds, weed control | 3-4 in | Thicker layer to choke weeds out from the start |
| Around trees | 2-3 in | Keep it off the trunk, no volcano piles |
| Refreshing old mulch | 1-2 in | Top up the color, don't rebuild the whole depth |
| Paths and play areas | 3-4 in | Deeper cushion that lasts |
If you mulched the bed last year, you only need an inch or two to bring the color back, not a full 3 inches. Set the refresh depth and you'll buy half the mulch.
A real example
A 20 by 10 foot bed at 3 inches deep is 200 square feet times 0.25 feet, or 50 cubic feet. That's 25 bags, or just under 2 cubic yards. At that size a bulk yard usually beats bagged once you add up the bag prices, which is exactly the comparison the cost field is for.
Mulch types and weight
Type matters for delivery and for what you're mulching. Hardwood and bark are the everyday choices. Rubber and dyed mulches last longer but don't feed the soil, and rubber has no place in a vegetable garden. Weight matters if you're hauling: a cubic yard of wood mulch runs roughly 400 to 800 pounds dry, heavier soaked, so a pickup bed handles a yard or two, not five.
Bagged or bulk
Bagged is simpler for small beds and you can carry it one bag at a time. Bulk saves real money past a dozen bags and skips the stack of plastic, but you pay a delivery fee and move the pile yourself. The cost estimate lets you price both for your exact square footage before you decide.
Mulch coverage chart
| Amount | At 2 in deep | At 3 in deep |
|---|---|---|
| 1 bag (2 cu ft) | 12 sq ft | 8 sq ft |
| 5 bags | 60 sq ft | 40 sq ft |
| 1 cubic yard | 162 sq ft | 108 sq ft |
| 2 cubic yards | 324 sq ft | 216 sq ft |
| 5 cubic yards | 810 sq ft | 540 sq ft |
The planning shortcut: one yard per 100 square feet of bed at 3 inches. Walk the yard, add up rough bed sizes, and you'll land within a bag or two of the calculator.
Quick answers
What kind of mulch lasts longest? Pine bark nuggets and cedar outlast shredded hardwood by a season or more. Dyed mulch holds color, not structure; it decomposes on the same schedule as plain hardwood.
Should I remove old mulch first? No, unless it's matted or moldy. Rake it loose, top up to your target depth, and let the old layer keep feeding the soil.
How much does a yard of mulch weigh? 600 to 800 pounds dry, close to double after heavy rain. One of the few materials a half-ton pickup hauls by the full yard.
Common questions
Measure your bed's length and width, pick a depth of 2 to 3 inches for most plantings, and the calculator converts that into bags and cubic yards. A rough rule: one cubic yard covers about 100 square feet at 3 inches deep.
Thirteen and a half. A cubic yard is 27 cubic feet and each bag holds 2, so 27 divided by 2 is 13.5 bags per yard. That's why bulk gets cheaper fast on bigger jobs.
Two to three inches for established beds. Too thin and weeds push through; too thick and you can suffocate roots and trap moisture against stems.
Bulk almost always wins per cubic foot, but you pay for delivery and you have to move it yourself. For small beds under a dozen bags, bagged is simpler. The cost estimate above lets you compare both for your size.
Estimates for planning. Verify against your supplier's units and your local building codes before ordering or building. For anything structural, follow your engineer or local code.