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Mulch Calculator
Use this free Mulch Calculator to find out how much mulch your garden beds need before you buy. Enter the size of the area and the depth you want, and it works out the volume in cubic yards and cubic feet, how many bags that is, and what it will cost — both as bulk mulch by the yard and as bagged mulch — so you can pick the cheaper option.
2–4 in is right for most beds; 3 in is standard.
Typical bulk mulch: about $30–$50 per yard.
Typical bagged mulch: about $3–$5 per 2 cu ft bag.
| Bed area | — |
| Volume (cubic feet) | — |
| Volume (cubic yards) | — |
| Bags needed | — |
| Bulk cost | — |
| Bagged cost | — |
How it works
Mulch is sold by volume, but beds are measured by area and depth, so the calculator bridges the two. First it finds the area of your beds in square feet — either by multiplying the length by the width, or by taking the total square feet you enter directly, which is handy for beds that are not neat rectangles. Then it multiplies the area by the depth, with the depth converted from inches to feet by dividing by 12, to get the volume in cubic feet. Finally it divides by 27, because there are 27 cubic feet in a cubic yard, and that is the unit bulk suppliers quote.
The bag count comes from dividing the cubic feet by the size of one bag. A 2 cubic foot bag is the most common size at garden centers, but 1 and 3 cubic foot bags are sold too, so pick the size you plan to buy. The calculator rounds the bag count up to a whole bag, because a half-covered bed is no good and a spare bag keeps well in a dry shed. The two costs are worked out separately: the bulk cost multiplies the exact cubic yards by your price per yard, and the bagged cost multiplies the rounded-up bag count by your price per bag. Comparing the two lines is usually the most useful part of the result — for a big bed the bulk price is often half the bagged price, while for a single small bed the bags can win once delivery fees are counted.
Depth is the number most people get wrong, so the depth guide below is worth a look before you order. Too thin and weeds push through within weeks; too thick and water struggles to reach the soil, while plant roots can grow up into the mulch instead of down into the ground. Three inches is the standard depth for a fresh bed, two inches is enough for a yearly top-up over mulch that is already there, and four inches suits a new bed or a weedy patch. If your beds have different depths — a fresh bed at 3 inches and a top-up at 2 inches, for example — run the calculator once for each group and add the results together.
Mulch depth guide and coverage table
Two to four inches covers nearly every garden job. Use 2 inches to refresh a bed that already has mulch, 3 inches for a standard fresh bed, and 4 inches for a new bed or one with stubborn weeds. Never go deeper than 4 inches around shrubs and trees, and keep mulch a few inches away from trunks and stems so bark stays dry and rot cannot start.
| Depth | Best for | Area covered by 1 cubic yard |
|---|---|---|
| 1 inch | Light dusting over existing mulch | 324 sq ft |
| 2 inches | Yearly top-up | 162 sq ft |
| 3 inches | Standard fresh bed | 108 sq ft |
| 4 inches | New bed, weedy patch | 81 sq ft |
Worked example
A flower bed measures 20 feet long and 15 feet wide, and it needs mulch 3 inches deep. Bulk mulch costs $45 per cubic yard, and bagged mulch costs $4.50 per 2 cubic foot bag.
Step 1: Area: 20 × 15 = 300 square feet.
Step 2: Depth in feet: 3 inches ÷ 12 = 0.25 feet.
Step 3: Volume: 300 × 0.25 = 75 cubic feet.
Step 4: Cubic yards: 75 ÷ 27 = 2.78 cubic yards.
Step 5: Bags: 75 ÷ 2 = 37.5, rounded up to 38 bags.
Step 6: Bulk cost: 2.778 × $45 = $125.00. Bagged cost: 38 × $4.50 = $171.00.
Enter those same numbers in the calculator — 20 ft by 15 ft, 3 in deep, 2 cu ft bags, $45 per yard, $4.50 per bag — and it gives exactly the same result: 2.78 cubic yards, 75 cubic feet, 38 bags, $125.00 in bulk or $171.00 bagged. Bulk mulch saves $46.00 on this bed, so a yard delivery is the better buy unless the truck cannot reach the garden.
FAQ
How deep should mulch be?
Two to four inches is the right depth for most garden beds. Three inches is the usual choice: deep enough to hold moisture and block weeds, but not so deep that it smothers plant roots. Use 2 inches for a light top-up over existing mulch, and 4 inches for a fresh bed or a spot with stubborn weeds. Never pile mulch against tree trunks or plant stems — leave a few inches of clear space so bark and stems stay dry.
How many cubic yards of mulch do I need?
Multiply your bed area in square feet by the depth in feet (depth in inches divided by 12) to get cubic feet, then divide by 27 to get cubic yards. For example, a 300 square foot bed at 3 inches deep needs 75 cubic feet, which is 2.78 cubic yards. Round up when ordering bulk mulch, because a thin spot is easy to fix with a spare wheelbarrow load but a short delivery is not.
How many bags of mulch make a cubic yard?
It depends on the bag size. A cubic yard is 27 cubic feet, so it takes about fourteen 2 cubic foot bags to make a yard, nine 3 cubic foot bags, or twenty-seven 1 cubic foot bags. Bags are handy for small beds and for carrying mulch through a gate a truck cannot reach, but bulk mulch by the cubic yard is usually much cheaper per cubic foot for larger jobs.
Is bulk mulch or bagged mulch cheaper?
Bulk mulch is almost always cheaper per cubic foot. Bulk hardwood mulch often costs $30 to $50 per cubic yard delivered, while bagged mulch at $3 to $5 for a 2 cubic foot bag works out to roughly $40 to $68 per cubic yard before delivery — and you still have to haul the bags. Bags win only for small jobs under a yard, or where a delivery truck cannot get close to the beds. This calculator shows both costs side by side so you can compare.
How much area does one cubic yard of mulch cover?
One cubic yard covers 324 square feet at 1 inch deep, 162 square feet at 2 inches, 108 square feet at 3 inches, and 81 square feet at 4 inches. The coverage halves as the depth doubles, because the same volume is spread thicker. Use the coverage table on this page to check your result, or enter your bed size in the calculator and let it work out the volume for you.