Calculate mulch volume for a rectangular bed in cubic yards, cubic feet and whole bags. A 20 x 5-foot bed at 3 inches needs 25 cubic feet, 0.9259 cubic yard or 13 two-cubic-foot bags. The result is net geometric volume, with no extra allowance. For a top-up, enter only the depth you need to add.
How the mulch calculator works
Cubic feet = length (feet) x width (feet) x depth (inches) / 12.
Cubic yards = cubic feet / 27.
Bags = cubic feet / printed bag volume, rounded up. One cubic yard is 3 x 3 x 3 = 27 cubic feet. Use the volume stated on your bag, not its weight. This form offers 2- and 3-cubic-foot bags and does not add a waste or settling percentage.
The form measures one rectangle. Use only the area you will mulch; do not include a walkway or lawn inside a larger bounding rectangle. For several beds, calculate each area, add their unrounded volumes, then round the combined bag count once if all use the same product. Rounding each bed separately can produce a different total.
Mulch volume chart by area and depth
Our calculated chart shows net cubic yards without allowance. Depths are examples. Select an appropriate total depth for your plants and material before ordering.
| Bed area | 2-inch new layer | 3-inch new layer | 4-inch new layer |
|---|---|---|---|
| 50 sq ft | 0.3086 yd³ | 0.4630 yd³ | 0.6173 yd³ |
| 100 sq ft | 0.6173 yd³ | 0.9259 yd³ | 1.2346 yd³ |
| 200 sq ft | 1.2346 yd³ | 1.8519 yd³ | 2.4691 yd³ |
| 300 sq ft | 1.8519 yd³ | 2.7778 yd³ | 3.7037 yd³ |
| 500 sq ft | 3.0864 yd³ | 4.6296 yd³ | 6.1728 yd³ |
| 1000 sq ft | 6.1728 yd³ | 9.2593 yd³ | 12.3457 yd³ |
How much area does one bag cover?
Coverage in square feet = bag volume in cubic feet x 12 / depth in inches. These are calculated geometric values. Product texture, actual spread depth and site shape affect the practical result.
| Layer depth | 2-cu-ft bag | 3-cu-ft bag | 1 cubic yard |
|---|---|---|---|
| 1 inches | 24.0 sq ft | 36.0 sq ft | 324.0 sq ft |
| 2 inches | 12.0 sq ft | 18.0 sq ft | 162.0 sq ft |
| 3 inches | 8.0 sq ft | 12.0 sq ft | 108.0 sq ft |
| 4 inches | 6.0 sq ft | 9.0 sq ft | 81.0 sq ft |
Three checked examples
1. A 20 x 5-foot bed at 3 inches
Area: 20 x 5 = 100 square feet. Volume: 100 x (3 / 12) = 25 cubic feet. Divide by 27: 0.925926 cubic yard, displayed as 0.9259. With 2-cubic-foot bags, 25 / 2 = 12.5, so round up to 13 bags. Thirteen bags contain 26 cubic feet, 1 cubic foot beyond the net target because bags are whole units.
2. A 12 x 8-foot bed with 3-cubic-foot bags
For an example 2-inch new layer: 12 x 8 x (2 / 12) = 16 cubic feet, or 0.592593 cubic yard. At 3 cubic feet per bag, 16 / 3 = 5.333333, rounded up to 6 bags. Those bags contain 18 cubic feet. The bag count does not include a separate allowance.
3. Topping up existing mulch
Suppose a 15 x 10-foot bed has 2 inches of usable mulch remaining and you choose a 3-inch total layer. The new depth is 3 – 2 = 1 inch. New volume: 15 x 10 x (1 / 12) = 12.5 cubic feet, or 0.462963 cubic yard. With 2-cubic-foot bags, 12.5 / 2 = 6.25, rounded up to 7 bags. Entering the full 3 inches would triple the estimated new material.
How deep should mulch be?
University of Minnesota Extension’s general mulching guide recommends a 2- to 4-inch layer, clear space around stems and trunks, and checking depth as organic mulch decomposes.1 The same guide notes that grass clippings should be applied in thin layers because matting can restrict oxygen. A depth range for bark or chips should not be treated as a universal rule for every material.
The 3-inch default is an example within that general range. For a top-up, check several places and enter the missing depth rather than burying an existing full layer. The source also advises removing existing weeds before mulching and keeping a 6-inch mulch-free ring around tree trunks.1 For circular beds or rings, use our tree mulch measuring guide; this rectangular form does not subtract a circular trunk opening automatically.
Bulk yards versus bags
One cubic yard contains exactly 27 cubic feet. That is 13.5 two-cubic-foot bags by volume, so 14 whole bags are needed to meet or exceed a full yard. It is exactly 9 three-cubic-foot bags. Do not call 13 two-cubic-foot bags a full yard: they contain only 26 cubic feet.
The bulk and bag results are two ways to supply the same volume, not quantities to add together. Bulk suppliers may order in set increments, and the calculator does not apply their rounding or delivery terms. For a price comparison, use the separate mulch bags-versus-bulk cost calculator with actual quotes and delivery charges. This form has no cost input.
Measuring irregular beds
Split an L-shaped bed into nonoverlapping rectangles. Calculate each at the same new depth and add volumes. Do not count an interior rectangle again if it is already part of a larger measured rectangle. For curved boundaries, use a measured shape formula or smaller sections; a bounding rectangle can overestimate. See our irregular-yard area guide.
Metric mode
Use the switch for length and width in meters and new depth in centimeters. The bag dropdown stays in the US package units it names. Equivalent metric entries give the same bag count. The default 20 x 5 feet by 3 inches becomes 6.096 x 1.524 meters by 7.62 centimeters: 0.707921 cubic meter before bag rounding, or 13 two-cubic-foot bags.
FAQ
Does the calculator include settling or waste?
No. It reports net geometric volume and rounds only the bag quantity. It does not predict shrinkage as organic mulch decomposes. If you choose an order allowance with your supplier, apply it once to the unrounded volume, not again after entering an already increased depth.
Can I enter the total bed area instead of length and width?
There is no separate area field in this form. For a known 100-square-foot area, using 100 feet by 1 foot gives the same geometric volume at the chosen depth. That input pair represents the area mathematically, not the bed’s actual shape.
Should I put weed fabric under wood mulch?
University of Minnesota Extension does not recommend landscape fabric under organic mulch such as shredded wood in its evergreen guidance. It distinguishes that from fabric under non-organic mulch such as rock or shredded rubber.2 Do not treat fabric as a required part of a wood-mulch project.
What if my bag is a different size?
Use the cubic-foot result and divide by your bag’s printed cubic-foot volume, then round up. For example, 25 cubic feet / 1.5 cubic feet per bag = 16.666667, so 17 whole bags. Do not select 2 cubic feet for a 1.5-cubic-foot package.
Sources
- University of Minnesota Extension: Mulching for Soil and Garden Health (layer depth, material differences, replenishment and trunk clearance; reviewed 2026)
- University of Minnesota Extension: Fertilizing Evergreens (organic mulch and landscape-fabric distinction; reviewed 2026)
What you’ll need
A plain checklist. Needs vary by project, so follow the instructions on your materials.
- Wheelbarrow and rake – to move and spread mulch.
- Landscape edging – keeps mulch in the bed and out of the lawn.
- Shovel or pitchfork – for loose bulk mulch.
- Weed removal before spreading – Extension recommends removing existing weeds; landscape fabric is not recommended under organic mulch in its evergreen guidance.1, 2
- Gloves – splinters and dust.
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Turn mulch quantities into a budget
Use our mulch cost guide to compare bagged, bulk and installed quotes with the same scope. Price the whole bags or supplier delivery increment you actually buy, not just the unrounded volume. Our bags versus bulk cost calculator compares your own bag and bulk prices. Check delivery, spreading and bed preparation separately, and do not add them again if an installed quote already includes them.