Mulch, Topsoil & Compost Calculator
Cubic yards, m³ and bags of mulch, soil or stone for any bed — with extension depths.
Beds and areas
Material and depth
Bags and prices
Bags of each size
| Bag | Bags | Holds | Left over |
|---|
Each area
| # | Shape | Area (m²) | Volume (m³) |
|---|
About the Mulch, Topsoil & Compost Calculator
Work out how much mulch, topsoil, compost or decorative stone to buy for flower beds, borders, tree rings and raised beds. Add each bed as a rectangle, circle, ring around a tree, triangle, L-shape or a known area, choose the material — its depth from university extension guidance fills in — and the calculator gives the volume in cubic yards, cubic feet, cubic metres and litres, the number of bags of any size, and the cost bagged or delivered in bulk.
For a raised bed it also splits the fill into topsoil and compost. Everything runs in your browser; nothing you type is sent anywhere.
How to use it
- Choose Metric or US units and describe each bed. Use Ring (around a tree) for tree rings — outer diameter, and the circle kept clear around the trunk — and How many for several identical beds.
- Pick the material. The depth fills in from the extension guidance shown under it; change it or tap a common depth.
- Add an extra allowance if the material will settle or the ground is uneven, and for a raised bed the share of compost in the fill.
- Choose the bag size you can buy, and add a bag price and a bulk price (per yd³ or m³, plus delivery) to see which is cheaper. Copy the result or download it as CSV.
Examples
200 ft² × 0.25 ft = 50 ft³ = 1.85 yd³ → 25 bags of 2 ft³ or 17 bags of 3 ft³
10 m² × 0.075 m = 0.75 m³ = 750 litres → 15 bags of 50 L or 10 bags of 75 L
π/4 × (1.2² − 0.3²) × 4 = 4.24 m² → 0.32 m³ = 318 L → 7 bags of 50 L
58.7 ft³ = 2.17 yd³: 46.9 ft³ of topsoil and 11.7 ft³ of compost
How it is calculated
Volume = area × depth × (1 + extra allowance), and bags = volume ÷ bag size, rounded up to whole bags. Areas are length × width for a rectangle, π/4 × diameter² for a circle, π/4 × (outer² − inner²) for a ring, Heron's formula for a triangle from its three sides, and the overall rectangle minus the cut-out corner for an L-shape.
Units follow the exact definitions in NIST SP 811 (1 ft = 0.3048 m): 1 yd³ = 27 ft³ = 0.7646 m³, 1 ft³ = 28.32 litres and 1 m³ = 1,000 litres. Clemson's rule of thumb — one cubic yard covers 324 ft² an inch deep — is the same arithmetic: square feet × depth in inches ÷ 324 = cubic yards.
How deep? The extension guidance behind the presets
- Mulch (shredded bark, wood chips, pine straw): fine-textured mulches 2–3 in; coarse ones such as pine bark nuggets up to 4 in; grass clippings and shredded leaves never more than 2 in, because they mat (Clemson HGIC 1604). Florida-Friendly Landscaping recommends 3 in and no more (UF/IFAS Gardening Solutions).
- Compost: start with 2 in (about 25% by volume) worked into the top 6 in of a bed (Clemson HGIC 1655); about 1 in tilled in before a new lawn (Clemson HGIC 1203).
- Topsoil: up to 3 in over heavy clay or eroded soil before a new lawn (Clemson HGIC 1203).
- Raised beds: fill to the height of the bed; unframed beds are 4–8 in high, and compost should be 10–20% of the fill (Clemson HGIC 1257).
- Decorative stone: 2–4 in of crushed rock (University of Arizona AZ1497); Clemson notes that 1 in of small rocks already controls weeds.
Laying it around plants and buildings
Keep mulch 2–3 in away from the stems of woody plants and 6–12 in away from the walls of buildings (Clemson HGIC 1604) — mulch piled against a trunk ("volcano mulching") invites rot and rodents. Clemson suggests a mulch circle 3–4 ft across for a newly planted tree and about 2 ft of diameter for each inch of trunk diameter for an established one; UF/IFAS suggests at least 8 ft across and keeping mulch about 1 ft from the base of large trees. Enter the cleared circle as the ring's inner diameter.
Bags or bulk?
Bags in the US are sold by the cubic foot (2 ft³ and 3 ft³ are common); elsewhere they are sold by the litre (40–100 L). A cubic yard is 13.5 bags of 2 ft³ or 9 bags of 3 ft³; a cubic metre is 20 bags of 50 L. Enter both prices — and the delivery fee for bulk — and the calculator shows which is cheaper for your volume. The table lists the bags of every common size, and how much would be left over.
Limitations
- Beds are treated as flat and the depth as even; slopes, edging and dips need more.
- Bulk mulch and compost are loose: what the supplier measures can settle in the truck and after spreading. Use the extra allowance for that — there is no single figure for every material.
- Weights are not shown: they depend on the material and how wet it is. For stone sold by the tonne use the gravel calculator.
- The depths are the extension services' general guidance; local advice for your climate, soil and plants comes first.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
How many bags of mulch make a cubic yard?
A cubic yard is 27 ft³, so 13.5 bags of 2 ft³ or 9 bags of 3 ft³. In litres it is 764.6 L — about 15.3 bags of 50 L or 10.2 bags of 75 L.
How much area does a cubic yard of mulch cover?
At 1 in deep it covers 324 ft²; divide by the depth in inches for any other depth — 162 ft² at 2 in, 108 ft² at 3 in and 81 ft² at 4 in. A cubic metre covers 20 m² at 50 mm and 13.3 m² at 75 mm.
How deep should mulch be?
For fine mulches such as shredded bark or pine straw 2–3 in (50–75 mm), for coarse bark nuggets up to 4 in, and no more than 2 in of leaves or grass clippings (Clemson HGIC 1604). UF/IFAS recommends 3 in and warns that more keeps water from the roots.
How do I enter a tree ring?
Choose Ring (around a tree). The outer diameter is the width of the mulched circle; the inner diameter is the trunk plus the gap you keep free around it (a few inches; about a foot for large trees). Set How many for several trees of the same size.
How much compost goes into a raised bed?
Clemson HGIC 1257 suggests compost as 10–20% of the bed's volume, the rest good topsoil. Choose Raised bed fill, set the depth to the height of the bed and the compost share, and the calculator splits the volume for you.
Should I order a little extra?
Loose material settles and ground is rarely flat, so many people round up. The calculator does not add anything unless you set the extra allowance; it then shows the volume with it and the bags for that volume.