Mulch Calculator: How Many Yards or Bags You Need
This mulch calculator guide gives you the exact formula and the worked math to size any bed: square footage times depth in inches, divided by 324, equals the cubic yards you need. Measure each bed, pick a depth, run the number, then round up about 10 percent for settling. The full method, a coverage lookup table, per shape formulas, and the bag versus bulk conversion are below. For what mulch actually costs per yard or per bag, see our 2026 mulch pricing guide; this page is the math.
The mulch calculator formula
The core formula is square footage times depth in inches, divided by 324, which gives cubic yards. The 324 is a constant: it folds together the 12 inches in a foot and the 27 cubic feet in a cubic yard, so you can go straight from a flat area and a depth in inches to a yardage. One cubic yard spread one inch deep covers 324 square feet, which is where the number comes from.
If you prefer to work in stages, multiply area in square feet by depth in feet (inches divided by 12) to get cubic feet, then divide cubic feet by 27 to reach cubic yards. Both routes land on the same answer. The single divide by 324 version is faster for a quick estimate; the two step version is easier to check.
| Step | What you do | Example (300 sq ft bed, 3 inch depth) |
|---|---|---|
| 1. Area | Length times width in feet | 300 sq ft |
| 2. Multiply by depth | Area times depth in inches | 300 times 3 = 900 |
| 3. Divide by 324 | Result is cubic yards | 900 divided by 324 = 2.78 cu yd |
| 4. Round up for settling | Add roughly 10 percent | Order 3 cu yd |
How much does a yard of mulch cover?
One cubic yard of mulch covers about 324 square feet at 1 inch deep, 162 square feet at 2 inches, 108 square feet at 3 inches, and 81 square feet at 4 inches. Depth and coverage move in inverse: double the depth and you halve the area one yard reaches. A cubic yard is 27 cubic feet, so these figures hold regardless of mulch type, since they are pure volume math, not weight.
Use the table below as a quick reference when you already know your square footage and want the yardage without doing the arithmetic. Find your depth column, then divide your total square footage by the coverage figure to get cubic yards.
| Depth | Coverage per cubic yard | Coverage per 2 cu ft bag | Typical use |
|---|---|---|---|
| 1 inch | 324 sq ft | 24 sq ft | Light refresh over existing mulch |
| 2 inches | 162 sq ft | 12 sq ft | Decorative beds, vegetable gardens |
| 3 inches | 108 sq ft | 8 sq ft | Standard new beds, around shrubs |
| 4 inches | 81 sq ft | 6 sq ft | Weed suppression, tree rings, paths |
How many bags of mulch are in a yard?
A cubic yard holds 27 cubic feet, so the bag count depends only on bag size. A standard 2 cubic foot bag gives 13.5 bags per yard, which most buyers round up to 14. A 3 cubic foot bag gives 9 per yard, a 1.5 cubic foot bag gives 18, and a 1 cubic foot bag gives 27. Divide 27 by your bag size to get the count for any package.
| Bag size | Bags per cubic yard | Bags for a 200 sq ft bed at 3 inches |
|---|---|---|
| 1 cu ft | 27 | 50 |
| 1.5 cu ft | 18 | 34 |
| 2 cu ft | 13.5 (round to 14) | 25 |
| 3 cu ft | 9 | 17 |
Bulk yardage is usually the cheaper unit once a project clears roughly 500 square feet, but that is a cost question, not a sizing one. For the bag versus bulk break even math and current price ranges, see our mulch pricing guide.
Calculating mulch for circles, triangles, and odd shapes
The divide by 324 formula needs a flat square footage first, so the only real work for non rectangular beds is finding the correct area. Use the shape formulas below to get square feet, then run the same depth and yardage steps. For a bed that is none of these shapes cleanly, break it into rectangles and circles you can measure, find each area, and add them together.
| Bed shape | Area formula (square feet) | Example |
|---|---|---|
| Rectangle or square | Length times width | 20 ft times 6 ft = 120 sq ft |
| Circle | 3.14 times radius times radius | Radius 5 ft: 3.14 times 25 = 78.5 sq ft |
| Triangle | Base times height, divided by 2 | 10 ft base, 8 ft height: 80 divided by 2 = 40 sq ft |
| Half circle (round bed end) | (3.14 times radius times radius) divided by 2 | Radius 4 ft: 50.24 divided by 2 = 25 sq ft |
| Irregular | Split into shapes above, sum the areas | Add each piece |
For a tree ring, measure the outer radius of the mulch circle and subtract the area of the trunk and any inner gap, since you are not mulching the trunk itself. Most homeowners skip that subtraction on small rings because it changes the yardage by a fraction. Our guide to measuring square footage covers the same area math for lawns and large irregular spaces.
What depth of mulch do I actually need?
A new bed wants 2 to 3 inches of mulch, and 3 inches is the common default for weed suppression and moisture retention without smothering roots. Refreshing a bed that still has old mulch needs only 1 to 2 inches to top it back up, so a refresh uses far less material than a fresh install. Going past 4 inches risks holding water against stems and starving roots of oxygen.
This new bed versus refresh split is the part most people get wrong, and it is why a refresh order should never use new bed numbers. If you laid 3 inches last year and an inch has broken down or compacted, you are topping up 1 to 2 inches, not 3, which can cut your yardage by half or more.
- Check what is already on the bed. Bare soil means a new install; existing mulch means a refresh.
- For a new bed, plan 3 inches (use 2 inches for vegetable gardens, up to 4 inches for tree rings and paths).
- For a refresh, plan 1 to 2 inches to bring the layer back to depth.
- Keep mulch 2 to 3 inches back from trunks and stems to avoid rot, regardless of bed depth.
A worked example, start to finish
Say you have two beds: one rectangle at 25 feet by 8 feet, and one circular bed with a 6 foot radius, both new installs at 3 inches deep. The rectangle is 200 square feet. The circle is 3.14 times 36, which is about 113 square feet. Total area is 313 square feet. Multiply by 3, divide by 324, and you need 2.9 cubic yards before settling.
Round up to 3 cubic yards for bulk, or buy 39 bags at 2 cubic feet each if you are bagging it. Adding a 10 percent settling and waste buffer to the raw 2.9 figure lands you at the same 3.2, which rounds to 3 yards. The settling buffer matters more on larger orders, where a 10 percent shortfall can leave a visible strip of bare bed.
| Bed | Area | Depth | Cubic yards |
|---|---|---|---|
| Rectangle (25 ft x 8 ft) | 200 sq ft | 3 in | 1.85 |
| Circle (6 ft radius) | 113 sq ft | 3 in | 1.05 |
| Total before buffer | 313 sq ft | 3 in | 2.90 |
| With 10 percent buffer | 3.19, order 3 cu yd |
Common mulch calculator mistakes
The errors that throw off a mulch order are almost always input errors, not math errors: mixing units, using new bed depth for a refresh, and forgetting the settling buffer. Each one tends to push you toward ordering too much or too little by a meaningful margin, so a quick check on these three before you buy is worth the minute.
- Mixing feet and inches: measure the bed in feet, but keep depth in inches and use the divide by 324 formula, or convert everything to feet first.
- Using new bed depth on a refresh: a top up is 1 to 2 inches, not 3, and this single mistake commonly doubles an order.
- Skipping the settling buffer: add roughly 10 percent because mulch compacts and some is lost in handling.
- Forgetting to subtract hardscape: do not mulch over pavers, stepping stones, or the trunk gap; subtract those areas first.
- Rounding down: always round the final yardage up, since coming up short means a second trip or a second delivery fee.
Mulch depth ties directly into bed health. If your beds are fighting weeds, compaction, or thin spots, depth alone will not fix them; our guides on diagnosing bare and damaged patches and renovating bare ground cover the underlying soil work. For broader project planning, the HMNDP learn hub collects the full set of lawn and landscape calculators and guides.
Last reviewed: June 2026
HMNDP Editorial Team, reviewed by HMNDP turf and horticulture editors.
Frequently asked questions
How much mulch do I need?
Multiply your bed’s square footage by the depth in inches, then divide by 324 to get cubic yards. A 300 square foot bed at 3 inches needs 2.78 cubic yards. Round up about 10 percent for settling, so order 3 yards. Measure every bed first, total the square footage, then run the formula once on the combined area.
How many bags of mulch are in a yard?
A cubic yard holds 27 cubic feet, so the bag count depends on bag size. A standard 2 cubic foot bag gives 13.5 bags per yard, usually rounded up to 14. A 3 cubic foot bag gives 9 per yard, a 1.5 cubic foot bag gives 18, and a 1 cubic foot bag gives 27. Divide 27 by your bag size.
How much does a yard of mulch cover?
One cubic yard covers about 324 square feet at 1 inch deep, 162 square feet at 2 inches, 108 square feet at 3 inches, and 81 square feet at 4 inches. Coverage halves each time you double the depth. These figures are pure volume math, so they hold for any mulch type regardless of weight.
How deep should mulch be?
A new bed wants 2 to 3 inches, with 3 inches the common default for weed control and moisture retention. Refreshing a bed that still has old mulch needs only 1 to 2 inches to top it up. Stay under 4 inches to avoid smothering roots, and keep mulch 2 to 3 inches back from trunks and stems.
Should I use cubic feet or cubic yards?
Use cubic yards for bulk mulch, since that is how delivery is sold and priced, and it is the cheaper unit on projects over roughly 500 square feet. Use cubic feet to count bags for small beds. Both come from the same formula: find cubic feet first, then divide by 27 to convert to cubic yards.
How do I calculate mulch for a circular bed?
Find the area with 3.14 times the radius times the radius, then run the standard depth formula. A bed with a 5 foot radius is 3.14 times 25, or about 78.5 square feet. At 3 inches deep that is 0.73 cubic yards. For odd shapes, split the bed into rectangles and circles, find each area, and add them.
How much does a yard of mulch weigh?
A cubic yard of wood mulch weighs roughly 400 to 800 pounds depending on moisture and wood type, and a 2 cubic foot bag runs about 25 to 40 pounds. Weight does not change the volume math: coverage and yardage depend only on cubic feet, so a heavier wet mulch covers the same area as a dry one.
Why round the mulch order up?
Mulch settles and compacts after spreading, and some is lost in handling and delivery, so add roughly 10 percent to your calculated yardage. Coming up short means a second trip or a second delivery fee, which costs more than a small surplus. The buffer matters most on larger orders where a 10 percent gap leaves a visible bare strip.