How this mulch calculator works
Mulching a bed comes down to one idea: volume = area × depth. Work out the area of the bed — length × width for a rectangle, or enter the square footage directly for an odd shape — then decide how deep you want the mulch to sit, and multiply. The result is a volume, which bulk suppliers quote in cubic yards (US) or cubic meters (metric), and which bagged mulch quotes in cubic feet.
The key is keeping units consistent. This tool converts your depth into the same unit as the area before multiplying, so a depth entered in inches is turned into feet first (divide by 12), and a depth in centimeters is turned into meters (divide by 100). If you are mulching several identical beds, set the number of beds and the volume is multiplied accordingly.
Once it has the volume, the calculator converts between cubic yards, cubic feet and cubic meters (1 cubic yard = 27 cubic feet). It then divides the volume by common bag sizes — 2 cu ft and 3 cu ft bags — rounding up so you never come up short. As a coverage rule of thumb, one 2 cu ft bag covers about 12 sq ft at 2 inches deep, and one cubic yard covers roughly 100 sq ft at about 3 inches deep. Bag sizes vary by brand and region, so always check the label.
Reference note: conversions use 1 cubic yard = 27 cubic feet and 1 cubic meter = 35.3147 cubic feet. Bag sizes vary between brands and countries, so the bag counts are estimates — round up and order a little extra to allow for settling and topping up as the mulch breaks down.
Mulch depth and coverage at a glance
| Depth | 2 cu ft bag covers | 3 cu ft bag covers | 1 cubic yard covers |
|---|---|---|---|
| 2 in | ~12 sq ft | ~18 sq ft | ~162 sq ft |
| 3 in | ~8 sq ft | ~12 sq ft | ~108 sq ft |
| 4 in | ~6 sq ft | ~9 sq ft | ~81 sq ft |
Frequently asked questions
- How much mulch do I need?
- Multiply the bed area by the mulch depth to get the volume, then divide by 27 to convert cubic feet to cubic yards. For example a 200 sq ft bed at 3 inches deep needs 200 × 0.25 = 50 cubic feet, which is about 1.85 cubic yards. This calculator does the conversions and also estimates how many bags you will need.
- How many bags of mulch are in a cubic yard?
- One cubic yard is 27 cubic feet, so it equals about 13.5 of the common 2 cu ft bags, or 9 of the 3 cu ft bags. Always round up to whole bags, and remember bag sizes vary by brand and region, so check the label before you buy.
- How deep should mulch be?
- Most gardens use 2 to 3 inches (about 5 to 8 cm) of mulch for flower beds and around shrubs, and 3 to 4 inches for weed suppression or moisture retention. Going much deeper than 4 inches can suffocate roots and waste material, and deeper mulch needs more volume.
- How many square feet does a bag of mulch cover?
- A 2 cu ft bag covers about 12 sq ft at 2 inches deep, or about 8 sq ft at 3 inches deep. A 3 cu ft bag covers about 18 sq ft at 2 inches deep. As a rule of thumb, one cubic yard covers roughly 100 sq ft at about 3 inches deep.
- What is the difference between cubic feet and cubic yards?
- A cubic yard is a block 3 ft × 3 ft × 3 ft, which equals 27 cubic feet. Bulk mulch is usually sold by the cubic yard, while bagged mulch is sold in cubic feet, commonly 2 or 3 cu ft bags. To convert cubic feet to cubic yards, divide by 27.
- Does the type of mulch matter for volume?
- For calculating volume, no — the math is the same whether you use wood chips, bark, straw or rubber, because volume is just area times depth. Type matters for weight, cost, settling and how often you top it up, but a given depth over a given area always needs the same cubic volume.