Landscaping
Mulch Calculator
Enter your bed size and depth, and this tells you the cubic yards to order or the bags to buy.
| Bed area | — |
|---|---|
| Depth, converted to feet | — |
| Volume needed | — |
| Divided by 27 cu ft per cu yd | — |
| Bags, rounded up | — |
UNITS CU FT
SOURCE /SOURCES/#mulch
What to buy
Paid links. If you buy through one, we earn a commission. Your price is the same. Nothing is listed here unless the calculator above says you need it.
Why this is more than you need
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Bagged wood mulch
The bag count above assumes the bag size you picked. Check the cubic feet on the bag, because 1.5, 2, and 3 cu ft all sit on the same shelf.
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Landscape edging
Mulch migrates. Edging is what keeps the depth you just calculated from ending up on the lawn.
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Landscape rake
Spreading to an even depth is the whole game. A wide rake makes 3 inches actually mean 3 inches.
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Wheelbarrow
Worth it past about a cubic yard, which is roughly 14 bags at 2 cu ft.
What the extensions recommend
| UMass Extension Landscape | 2 to 3 inches | and never more |
|---|---|---|
| University of Florida IFAS | 2 to 3 inches | Florida-Friendly Principle 4 |
Not a manufacturer spec. Two university extensions, agreeing, which is the closest thing to a standard mulch depth has.
Gear for the job
The calculator above does not count any of this. It is what the job takes to actually do. Paid links, and your price is the same.
- Mulch fork A shovel fights bagged bark. A fork lifts it in one motion, which matters at twenty-plus bags.
- Landscape fabric It goes under the mulch, not over it. Fabric on top traps the mulch and starves the soil.
- Heavy-duty tarp Dragging a loaded tarp beats twenty wheelbarrow trips on a small yard with tight gates.
- Edging spade A cut edge is what keeps mulch in the bed instead of on the lawn after the first rain.
- Garden gloves Bark mulch is rough, and hardwood mulch runs hot enough in the bag to be unpleasant bare-handed.
Part of a bigger job
This calculator sizes one material. These jobs need it along with others, and the list says what else to buy and in what order.
- Plant a bed soil, compost and mulch together, topsoil and compost, gravel
Depth is the whole calculation. The same bed at 2 inches versus 4 inches is twice the mulch and twice the money, and going deeper than 3 inches actively works against the plants you are mulching.
How to estimate mulch for a bed
Mulch is sold by volume and spread by depth, so the whole calculation is area times depth. The only trap is units: your bed is in feet, your depth is in inches, and the mulch is in cubic feet or cubic yards.
cubic feet = bed area (sq ft) × depth (in) ÷ 12
cubic yards = cubic feet ÷ 27Dividing by 12 turns inches into feet. Dividing by 27 turns cubic feet into cubic yards, because a cubic yard is 3 × 3 × 3 feet.
Measuring the bed
Rectangles are easy: length times width. For a curved bed, break it into rectangles and add them up, or measure the average width and multiply by the length. Being off by a foot on a border bed changes the answer by less than a bag.
For a circle around a tree, use radius times radius times 3.14. A 6 foot circle has a 3 foot radius, so 3 × 3 × 3.14 is about 28 square feet.
How deep, and why not deeper
Two to three inches. That range is not a guess. UMass Extension recommends 2 to 3 inches and adds "never more". The University of Florida's Florida-Friendly Landscaping program gives the same 2 to 3 inches and says to top up to maintain it. Michigan State horticulture puts 3 inches as the starting point for the main benefits.
Use 2 inches on established beds where there is already a layer, and 3 on new plantings where you are starting from bare soil. Four inches is defensible if weed suppression is the whole point and nothing is planted close, but it is the ceiling, not the target.
Deeper is actively worse. Piled mulch holds moisture against stems and trunks, and a thick mat can shed water instead of letting it through. The volcano of mulch around a tree trunk is the classic version of this mistake.
Bags or bulk
This is the real buying decision, and it turns on volume rather than price per unit.
A cubic yard is 27 cubic feet. At the common 2 cubic foot bag, that is 13.5 bags, so 14. Bag sizes are not standard: 1.5, 2, and 3 cubic feet all sit on the same shelf, and the number of bags changes by nearly half between the smallest and largest. Always read the cubic feet on the bag rather than counting bags from someone else's estimate.
Under about two cubic yards, bags win on convenience. You can fit them in a car, store the extras, and open only what you need. Past two cubic yards, you are opening 27 or more bags and dealing with the plastic, and bulk delivery is usually both cheaper per yard and far less work. That crossover is a handling judgment, not a spec, so treat it as a nudge and price both.
What one cubic yard actually covers
Useful to carry in your head, because it turns a delivery quote into a picture of your yard. One cubic yard spreads to roughly 160 square feet at 2 inches, 108 square feet at 3 inches, and 81 square feet at 4 inches. That is the same division as above, run backwards: 27 cubic feet divided by the depth in feet.
So a single yard covers a bed about 10 by 10 feet at a comfortable 3 inches. If your beds add up to more ground than that, you are into multiple yards, and it is worth measuring properly rather than guessing at the counter.
A quick cost check
Take a 20 by 10 foot bed at 3 inches. That is 200 square feet, 50 cubic feet, about 1.9 cubic yards, or 25 bags at 2 cubic feet. At $4 a bag that is $100. At $45 a delivered cubic yard it is about $85 plus whatever the delivery fee is. Close enough that convenience decides it, which is exactly the point where the crossover sits.
Common estimating mistakes
- Forgetting to divide by 12. Multiplying 200 square feet by 3 gives 600, not 50. Depth has to be in feet before it multiplies cleanly into cubic feet.
- Assuming every bag is 2 cubic feet. It is the most common size, not the only one, and a 1.5 cu ft bag needs a third more bags for the same bed.
- Adding a full layer over old mulch. Measure what is already there and top up to your target depth instead.
- Ordering exactly. Beds are rarely perfect rectangles, and settling costs you a little depth. Rounding up to the next bag or quarter yard is normal.
- Using this for rock or rubber. The volume math holds, but those are often sold by weight, so the bag count will not transfer.
When to hand it off
Mulch is not dangerous work, so the honest boundary here is about volume rather than safety. Past three or four cubic yards you are moving several tons of material by wheelbarrow, and a delivery plus a couple of hours of help is usually worth it.
One real caution: bagged mulch left sealed and wet can go anaerobic and turn sour, which will damage plants. If a bag smells like vinegar or ammonia when you open it, spread it out to air before it goes anywhere near a plant.
Questions
How many bags of mulch are in a cubic yard?
It depends on the bag. A cubic yard is 27 cubic feet, so it takes 14 bags at 2 cu ft, 18 bags at 1.5 cu ft, or 9 bags at 3 cu ft. Two cubic feet is the most common size, so 13.5 bags rounds to 14.
How deep should mulch be?
Two to three inches for most beds. University extension programs are consistent on this: UMass Extension recommends 2 to 3 inches and says never more, and the University of Florida's Florida-Friendly Landscaping program gives the same 2 to 3 inch range. Use 2 inches on established beds and 3 on new plantings. Deeper is not better, because piled mulch holds water against stems and roots.
Is bulk mulch cheaper than bags?
Past about two cubic yards, usually yes. Two cubic yards is 27 bags at 2 cu ft each, which is a lot of plastic to open and haul. Below that, bags are easier to move and store. This calculator shows both numbers so you can price the same volume each way.
Do I need to remove the old mulch first?
Usually not. Measure the depth you already have and top up to your target rather than adding a fresh full layer on top. If the existing mulch is already 3 inches deep and matted, rake it loose instead of burying it.
Does this work for rubber mulch or rock?
The volume math is identical, since it is just area times depth. The buying part is not. Rubber and stone are sold by weight as often as by volume, so convert using the weight per cubic foot on the product rather than assuming bags.
Every constant on this page is logged with its source and the date it was checked on the sources page.