Mulch Calculator
How much mulch for your garden beds? Enter bed size and depth to get cubic yards needed plus 2 cu ft bag equivalents.
This free mulch calculator saves you from guessing at the garden center. Enter your bed length, width, and mulch depth in inches, and get the cubic yards for a bulk delivery plus how many standard 2 cu ft bags you would need instead.
2-4" typical for flower beds.
How to use this calculator
- Step 1: Measure your bed length and width in feet (for irregular beds, break them into rectangles).
- Step 2: Enter your target mulch depth in inches — 3 is typical for flower beds.
- Step 3: Click Calculate to see cubic yards, cubic feet, and the number of 2 cu ft bags.
- Step 4: Compare bulk vs bags — over about 2 yards, bulk delivery is usually much cheaper.
The formula
Cubic feet = length x width x (depth/12). Cubic yards = cubic feet / 27. Bags = round up(cubic feet / 2).
Worked example
A 10x10 ft bed at 3 inches deep needs 25 cubic feet of mulch — that is 0.93 cubic yards, or 13 standard 2 cu ft bags. A full 12-inch-deep new bed the same size needs 3.7 yards (50 bags).
Frequently Asked Questions
How deep should mulch be?
Two to four inches is the sweet spot for flower beds and around trees — deep enough to suppress weeds and hold moisture, shallow enough for water and air to reach the soil. Never pile mulch deeper than 4 inches, and keep it pulled back a few inches from plant stems and tree trunks to prevent rot.
How often do I need to re-mulch?
Plan on topping up once a year. Organic mulch decomposes about an inch per year, so a 3-inch bed is down to 2 inches after a season. You usually only need to add an inch or two to refresh it, not redo the full depth — measure the current depth and top up to your target.
Is it cheaper to buy mulch in bulk or in bags?
Bulk wins once you need around 2 cubic yards or more — a bulk yard typically costs less than the equivalent in 2 cu ft bags, sometimes half as much. Bags are easier for small beds, precise top-ups, and when you have no way to get a truckload delivered. This calculator gives you both numbers so you can compare.
What type of mulch should I use?
Shredded hardwood bark is the all-around choice for beds — it mats together, resists washing away, and breaks down into good soil. Pine straw works well in the Southeast and around acid-loving plants. Dyed mulches look sharp but fade within a season. Avoid fresh wood chips directly against plant stems, and never use mulch as a substitute for fixing drainage problems.