Mulch Calculator
A 12 ft × 10 ft bed 3 inches deep needs about 1.11 cu yd (30 cu ft) of mulch, or 15 bags of 2 cu ft.
Updated · US units: feet, inches, cubic yards · Built and checked by AI, which can make mistakes
Work out how much mulch you need
Result
This is an estimate. Real quantities depend on uneven ground, settling, compaction and the exact product, and bag sizes and weights vary by brand. Check the bag or ask your supplier before you buy.
Built and checked by AI. AI wrote this calculator and its explanations, researched the rates and ran the tests. AI can make mistakes, and the checks may not catch them all, so confirm anything important with an official source or a qualified professional. How we use AI.
Quick answer
A 12 ft × 10 ft bed 3 inches deep needs about 1.11 cu yd (30 cu ft) of mulch, or 15 bags of 2 cu ft.
In Australia? Use our Australian mulch calculator, in cubic metres and litres.
How to use the mulch calculator
- Choose the shape of the area: a rectangle, a circle, or enter the area if you already know it.
- Enter the measurements in feet and the depth in inches.
- Pick the bag size you plan to buy.
- Optionally open “Compare costs” to see whether bags or bulk is cheaper.
- Press Calculate to see how much you need, with the steps.
How it’s calculated
Area = length × width (sq ft), or π × (diameter ÷ 2)² for a circle
Volume (cu ft) = area (sq ft) × depth (in) ÷ 12
Cubic yards = cubic feet ÷ 27
Bags = cubic feet ÷ cubic feet per bag, rounded up
Worked example
Mulch for a 12 ft × 10 ft area at 3 inches
- Area: 12 ft × 10 ft = 120 sq ft.
- Volume: 120 sq ft × 3 in ÷ 12 = 30 cu ft.
- In cubic yards: 30 cu ft ÷ 27 = 1.11 cu yd.
- Bags: 30 cu ft ÷ 2 cu ft per bag = 15, rounded up to 15 bags.
How deep should mulch be?
University extension services generally recommend 2 to 4 inches of mulch. The University of Illinois suggests 2 to 3 inches for composted mulch and 3 to 4 inches for coarse mulch, and the University of Florida recommends 2 to 3 inches on plant beds.
Keep mulch away from tree trunks and plant stems. The University of Illinois says to keep it at least 4 inches from trunks, because mulch piled against bark can cause rot and invite pests and disease.
When you’d actually use a mulch calculator
- Refreshing garden beds in spring. Work out how many bags to grab before you get to the store.
- Deciding between bags and bulk. Compare the cost of bags with a delivered load.
- Mulching around new trees. Use the circle option for the ring around each trunk.
What this calculator doesn’t include
- Irregular shapes. Split the area into rectangles and circles and add the results.
- Settling and compaction. Organic materials settle after watering, so you may need a little more.
- Delivery fees, minimum orders and local prices, which vary by supplier.
How we calculate
Area comes from your measurements. Volume is area × depth ÷ 12, converted to cubic yards by dividing by 27. We calculate at full precision and round only for display. Bag counts are rounded up to whole bags.
Sources:
Frequently asked questions
How many bags of mulch are in a cubic yard?
There are 27 cubic feet in a cubic yard, so it takes 13.5 bags of 2 cu ft mulch, or 18 bags of 1.5 cu ft, to make a cubic yard.
How deep should mulch be?
University extension services generally recommend 2 to 4 inches: 2 to 3 inches for fine or composted mulch and 3 to 4 inches for coarse bark. Keep it away from trunks and stems.
How much area does a bag of mulch cover?
A 2 cu ft bag covers about 8 square feet at 3 inches deep, or 12 square feet at 2 inches.