Mulch Calculator
Work out how much mulch a garden bed needs. Depth starts at 3 inches; get cubic yards, bags of 2 and 3 cubic feet, truck loads, an optional cost, and a table of the area one cubic yard covers at each depth.
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Enter the dimensions to see the volume.
About the mulch calculator
The Mulch Calculator tells you how much mulch to order for a garden bed, a tree ring or a whole set of borders. Choose the shape of the bed, enter its measurements and the depth you want to spread, and the calculator returns the volume in cubic yards, cubic feet, cubic metres and litres. It also converts that volume into a number of bags, a number of truck loads and, if you enter a price, an estimated cost.
Mulch is sold two ways: by the bag at a garden centre, or loose by the cubic yard from a landscape supplier. Bags are handy for small jobs. Bulk delivery is usually cheaper per unit once you need more than a few cubic yards. Seeing both numbers side by side makes the comparison easy.
How to calculate how much mulch you need
Steps
- Pick the shape: rectangle, circle, triangle, trapezoid, or known area if you already have the square footage.
- Enter the measurements. Each length has its own unit, so you can mix feet, inches, yards, metres, centimetres and millimetres.
- Check the depth. It is pre-filled with 3 inches, which you can change.
- If you have several identical beds, set the quantity instead of measuring each one again.
- Add a waste allowance if you want a margin. It starts at zero.
- Read the volume, bag counts and truck loads. Enter a price per cubic yard, per cubic metre or per bag to see an estimated cost.
Formulas
The volume is the bed area multiplied by the depth.
Bags are rounded up, because you cannot buy part of a bag.
Cubic yards come from cubic feet using the fact that a yard is 3 ft, so a cubic yard is 27 cubic feet.
For a circle the area is , where is the diameter. For a triangle it is half the base times the height, and for a trapezoid it is the average of the two parallel sides times the height. If you want to check the area on its own first, the Area Calculator handles the same shapes.
Worked example: a rectangular bed
A bed measures 20 ft by 10 ft and you want 3 inches of mulch. The area is 200 square feet and the depth is 3/12 = 0.25 ft, so the volume is 200 x 0.25 = 50 cubic feet. Divide by 27 and you get 1.85 cubic yards, which is about 1.42 cubic metres.
In bags, that is 25 bags of 2 cubic feet or 17 bags of 3 cubic feet (50 / 3 = 16.7, rounded up). At a price of 35 per cubic yard, the bulk cost is about 64.81. Compare that with your local bag price multiplied by 25 or 17 to see which option is cheaper.
Worked example: round beds and repeated beds
A circular bed 8 ft across at 3 inches deep has an area of about 50.3 square feet, so the volume is about 12.6 cubic feet, or 0.47 cubic yards. That is 7 bags of 2 cubic feet or 5 bags of 3 cubic feet.
For four identical square planting beds, each 4 ft by 4 ft and mulched 2 inches deep, enter one bed and set the quantity to 4. Each bed needs 16 x (2/12) = 2.67 cubic feet, so the total is 10.67 cubic feet, or about 0.40 cubic yards.
How far does a cubic yard of mulch go?
One cubic yard is 27 cubic feet, so the area it covers is 27 x 12 divided by the depth in inches. The table shows the result for common depths.
| Depth | Area covered by 1 cubic yard |
|---|---|
| 1 in | 324 sq ft |
| 2 in | 162 sq ft |
| 3 in | 108 sq ft |
| 4 in | 81 sq ft |
Doubling the depth halves the area, which is why a small change in depth makes a big difference to the amount you buy.
Choosing a depth
Typical advice is 2 to 3 inches around established plants. Thicker layers can hold too much moisture and starve roots of air, while thin layers let weeds through. Keep mulch away from tree trunks and plant stems, leaving a gap of a few inches so the bark can stay dry. Mulch breaks down and thins out, so many gardeners top up each year rather than starting over. These are typical guidelines only. Your plants, climate and soil may call for something different, so follow local advice.
Bags, bulk and truck loads
Bag sizes of 2 and 3 cubic feet are common, but products vary, so check the volume printed on the bag label. For bulk orders, the truck loads figure uses a capacity you can edit, with 10 cubic yards as the default. Ask your supplier what they actually deliver, as loads, minimum orders and delivery fees differ. For other loose materials, see the Gravel Calculator and the Topsoil Calculator.
Accuracy and limits
Results are estimates. Beds are rarely perfectly flat, mulch settles after spreading, and some is lost at the edges. If you want a safety margin, use the waste allowance. The calculator does not include a weight field, because mulch density varies a lot with moisture and material. If you need to compare cubic yards with cubic metres or litres elsewhere, the Volume Converter can help.
Privacy
Nothing is uploaded; every calculation runs in your browser and never leaves your device.
Related tools
For measuring beds, use the Area Calculator or the Length Converter. To estimate soil for the same project, try the Topsoil Calculator or the Soil Calculator, and use the Unit Price Calculator to compare bag and bulk prices.
Frequently asked questions
How do I calculate how much mulch I need?
Multiply the bed area by the depth to get a volume, then convert it to cubic yards by dividing cubic feet by 27. For example, a 20 ft by 10 ft bed at 3 inches deep is 50 cubic feet, or about 1.85 cubic yards.
How deep should mulch be?
A typical depth is 2 to 3 inches around established plants. Keep mulch off tree trunks and plant stems, and top it up as it breaks down, usually once a year. Check local advice for your plants and climate.
How much area does one cubic yard of mulch cover?
One cubic yard covers about 324 square feet at 1 inch, 162 at 2 inches, 108 at 3 inches and 81 at 4 inches. The area is 27 cubic feet times 12 divided by the depth in inches.
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, which is 13.5 bags of 2 cubic feet or 9 bags of 3 cubic feet. The calculator rounds up the bags for your actual volume. Check the bag label, because sizes vary by brand.
Is it cheaper to buy mulch in bags or in bulk?
Bulk is often cheaper per cubic yard for larger jobs, while bags suit small beds and avoid delivery fees. Enter a price per yard, per cubic metre or per bag to see an estimated cost, and ask your supplier about minimum orders and delivery charges.
Can I use different units and several beds?
Yes. Each length has its own unit (feet, inches, yards, metres, centimetres or millimetres), and the quantity field repeats one bed measurement for identical beds. Results show in cubic yards, cubic feet, cubic metres and litres.
Is my data sent anywhere?
No. The bed volume, bag count and cost sums run in your browser, so your bed sizes and prices are never uploaded or stored on a server. They stay on this device and are not shared with anyone.