How to use this mulch calculator
- Units, choose Feet or Metres for your bed measurements.
- Mulch material, pick shredded bark, wood chips, straw, pine straw or rubber mulch to load a typical bag or bale size, or choose Custom to type your own.
- Length and width, enter the dimensions of the rectangular bed.
- Depth, enter how thick you want the mulch layer (inches in Feet mode, centimetres in Metres mode).
- Bag or bale size, adjust this in cubic feet if your product's packaging differs from the preset.
- Read the cubic yards, cubic feet and bags/bales needed, they update instantly as you type.
- Add another bed for every extra planting area, each one gets its own volume and bag count, plus a combined total for the whole job.
How to calculate mulch
Mulch is sold by volume, so the calculation is simply volume = area × depth. First find the area of the bed by multiplying length by width, then multiply by the depth to get the volume. The trick is keeping your units consistent: depth is usually given in inches or centimetres, so it has to be converted to the same unit as length and width before multiplying. In Feet mode this calculator divides the depth in inches by 12; in Metres mode it divides the depth in centimetres by 100, then converts the result to cubic feet.
From there the conversions are fixed. 1 cubic yard = 27 cubic feet, so the calculator divides the total cubic feet by 27 to give cubic yards, the unit bulk mulch is usually sold in. To find bags or bales it divides the total cubic feet by your bag or bale size and rounds up, since you can only buy whole ones. A layer of 2 to 3 inches is typical for most beds, deep enough to hold moisture and slow weeds without smothering roots.
Bag and bale sizes vary a lot by material. A standard bag of shredded bark mulch holds about 2 cubic feet, wood chips are often sold in larger 3 cubic foot bags, and rubber mulch bags are commonly 1.5 cubic feet. Straw and pine straw are sold by the bale instead, and a bale spreads over less ground than its size suggests once you account for a normal 2 to 3 inch mulch depth. These are general figures from typical retail packaging, not a guarantee for every brand, so check your own bag or bale before buying in bulk.
Note: This calculator assumes rectangular beds and a flat, even layer. Real beds settle and ground is rarely perfectly level, so it is wise to buy a little extra. Each bed's bag or bale figure is rounded up on its own, then added to the combined total, so the total may be a little higher than dividing the combined volume by the bag size directly.
Frequently asked questions
How much mulch do I need for my garden bed?
Multiply the bed length by the width to get the area, then multiply by the depth to get the volume. For a 10 ft by 10 ft bed at a 3 inch depth, that is 100 sq ft times 0.25 ft, or 25 cubic feet, which is just under one cubic yard.
How many cubic feet are in a cubic yard?
One cubic yard equals 27 cubic feet. So if your bed needs 54 cubic feet of mulch, that is 2 cubic yards.
How many bags of mulch are in a cubic yard?
A standard bag holds about 2 cubic feet. Since a cubic yard is 27 cubic feet, you need roughly 13.5 bags to make one cubic yard.
How thick should the mulch be?
A layer of 2 to 3 inches is typical for garden beds, deep enough to hold moisture and suppress weeds without smothering plant roots.
Does the type of mulch change how many bags I need?
Yes. A standard bag of shredded bark is about 2 cubic feet, wood chips are often sold in larger 3 cubic foot bags, and rubber mulch bags are commonly 1.5 cubic feet. Straw and pine straw are sold by the bale rather than the bag. Picking a material preset in the calculator swaps in a typical figure for that type, so the bag or bale count updates automatically.
Can I calculate mulch for more than one garden bed?
Yes. Use the Add another bed button to enter as many beds as you need, each with its own length, width and depth. The calculator shows the volume and bags for every bed plus a combined total for the whole job.