A fresh layer of mulch holds moisture in the soil, keeps weeds down and evens out soil temperature, but it is surprisingly easy to over- or under-buy. This calculator turns the size of your beds and the depth you want into cubic yards for bulk delivery and a bag count for the size sold at your garden center, and compares the cost of both if you enter prices.
How to use the mulch calculator
- Choose the shape of the bed — rectangle, circle, triangle — or enter a known area. For several beds, total their square footage with the square footage calculator and use Known area.
- Enter the mulch depth. If old mulch remains, enter only the depth you are adding.
- Pick the bag size you plan to buy.
- Optionally enter a price per bag and a bulk price per cubic yard to compare.
Mulch formulas
The shortcut for cubic yards straight from square feet and inches is area × depth ÷ 324.
Worked example
Beds totaling 200 ft², mulched 3 inches deep:
200 × 3 ÷ 12 = 50 ft³; 50 ÷ 27 = 1.85 yd³
In 2 cu ft bags: 50 ÷ 2 = 25 bags. At $4.50 a bag, that is $112.50.
In bulk, rounded up to 2 yd³ at $38 a yard: $76 plus any delivery fee.
How deep to mulch
| Mulch type | Typical depth | Notes |
|---|---|---|
| Shredded hardwood or cedar | 2 – 3 in | Knits together; good on slopes |
| Pine bark nuggets | 3 – 4 in | Coarse; lasts longer, can float in heavy rain |
| Pine straw | 3 – 4 in when fresh | Settles to about 2 in |
| Wood chips | 3 – 4 in | Economical for paths and large areas |
| Rubber mulch | 2 – 3 in | Heavy and long-lasting; mainly for play areas |
For stone mulch, which is sold by weight, use the gravel calculator.
Bags or bulk?
Bags are convenient: they fit in a car, store neatly and let you buy exactly what you need for small beds. Bulk mulch is delivered loose or loaded into a truck at the yard and is typically far cheaper per cubic yard, but suppliers often charge a delivery fee or have a minimum order. As a rough guide, bags win for jobs under about a cubic yard, bulk wins above two or three, and in between it depends on local prices. Have bulk mulch dumped on a tarp close to the beds to save wheelbarrow trips.
Mulching tips
- Keep mulch 2 to 3 inches away from tree trunks and plant stems. Piling it against bark — so-called volcano mulching — traps moisture and invites rot and pests.
- Organic mulch breaks down over time, so most beds need about an inch topped up each year rather than a full new layer.
- Water the soil well before mulching dry beds; mulch keeps moisture in but can also slow light rain from getting through.
To see how far a given amount of mulch will stretch, use the mulch coverage chart.
Frequently asked questions
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cubic feet, 9 bags of 3 cubic feet, 18 bags of 1.5 cubic feet or 27 one-cubic-foot bags.
How much area does a yard of mulch cover?
One cubic yard covers about 162 square feet at 2 inches deep, 108 square feet at 3 inches and 81 square feet at 4 inches. The mulch coverage chart lists more depths and bag sizes.
How deep should mulch be?
Two to three inches is typical for shredded mulch and three to four inches for coarse bark nuggets. Thinner layers let weeds through, while layers much deeper than four inches can keep soil too wet and limit air reaching roots.
Is bulk mulch cheaper than bags?
Usually, once you need more than two or three cubic yards. Bulk mulch often costs much less per yard than the equivalent number of bags, but delivery fees can wipe out the savings on small orders. Enter both prices to compare.
Do I need to remove old mulch first?
Not usually. If last year's layer is still an inch or two deep, measure what is there and only add enough to reach your target depth. Remove it if it has matted into a crust or is causing drainage problems.