How much mulch, soil, or gravel do you actually need?
Enter the size of your bed and how deep you want the material, and this calculator
returns the exact volume in cubic yards and cubic feet — plus how many bags to buy in
the common sizes. The math is the same formula a garden center uses, and it's shown
below the answer so you can check it. Depth recommendations are sourced from university
extension services, not invented.
Rectangle or circle·Cubic yards, cubic feet & bag counts·Formula shown
Read this first
This tool calculates volume — the amount of material that fills your area to the
depth you choose. Volume math is exact. Anything about weight (for hauling) or
recommended depth (for plant health) is approximate and varies with material,
moisture, and your specific plants — those figures are given as ranges and cited to their
sources. Order about 5–10% extra to cover settling, uneven ground, and spillage.
Pick your area shape, enter the dimensions and depth, and choose your material. You'll get cubic yards, cubic feet, and how many bags you need in the common sizes for that material.
Measure straight across the widest point of the circle.
Bags needed (rounded up — partial bags aren't sold)
Tip: order about 5–10% more than the exact figure to allow for settling, uneven ground, and spillage.
Tool 2 · Depth helper
What depth should I use?
Choose what you're doing and get the depth range university extension services recommend. Use it to fill in the depth field above. These are guidelines — your plants and soil drainage come first.
A quick reality check
One cubic yard covers about 324 sq ft at 1 inch deep
That single fact is the backbone of every coverage chart: 27 cubic feet ÷ (1 inch ÷ 12)
= 324 square feet per inch of depth. So a yard covers ~162 sq ft at 2 inches, ~108 sq ft
at 3 inches, and ~81 sq ft at 4 inches. If you'd rather not do the arithmetic, the
calculator above handles it and shows the steps.
Recommended depth & coverage chart
Depth ranges drawn from university extension and horticulture sources. Where the standard
guidance is a range, the range is shown — these are not invented precise numbers. The
coverage column is the exact area one cubic yard covers at that depth (324 ÷ depth in
inches).
Use case
Recommended depth
What 1 cubic yard covers at that depth
Notes & source
Mulch — flower & shrub beds
2–3 in
~108–162 sq ft
2–3 in gives the weed-suppression and moisture benefit without smothering roots. Coarser wood/bark mulch can go to 3–4 in (CSU Extension).
Mulch — around trees
2–4 in
~81–162 sq ft
2–4 in on well-drained soil, less on poorly drained soil; keep it pulled back from the trunk, never piled against bark (Penn State Extension).
Mulch — fine-textured
1–2 in
~162–324 sq ft
Finely shredded mulches pack tighter and restrict oxygen, so apply thinner than coarse mulch (Penn State Extension).
Topsoil — new lawn (seed/sod)
4–6 in
~54–81 sq ft
A settled 4–6 in of quality topsoil supports turf rooting; blend the lower portion into the existing subsoil (Penn State Extension, lawn establishment).
Topsoil / garden soil — new bed
6–12 in
~27–54 sq ft
Deeper for vegetables and deep-rooted plants; 6 in is a common minimum for a raised bed of mixed planting.
Compost — amending soil
1–3 in
~108–324 sq ft
Spread 1–3 in over existing soil and till in; a thin top-dress (¼–½ in) is typical for established lawns.
Gravel — paths & beds
2–4 in
~81–162 sq ft
Inorganic mulches like gravel are commonly applied 3–4 in deep (CSU Extension); decorative beds often 2–3 in over fabric.
Gravel — driveway (per layer)
3–4 in
~81–108 sq ft
Driveways are built in compacted lifts; total depth is usually several layers. Confirm the spec with your supplier or contractor.
Depth ranges are general guidance from the cited extension/horticulture sources; your
specific plants, soil drainage, and climate take priority. Coverage figures are exact
(324 ÷ depth in inches) and assume material spread evenly with no compaction.
What changes how much you need
Depth, not area, is where people go wrong
Doubling the depth doubles the material; the area is usually measured well, but "3 inches" quietly becomes 4 or 5 when you're spreading by hand. Decide your depth from the chart above, then stick to it. An extra inch across a large bed is a surprising amount of extra material — and, for mulch around plants, can be harmful rather than helpful.
Settling and compaction
Loose material settles. Mulch and compost compress over a season; gravel and soil compact under their own weight and foot traffic. The calculator gives the volume to fill your space as measured — adding roughly 5–10% covers settling and the inevitable spillage. For a compacted gravel base, your supplier may recommend ordering more because compacted depth is less than loose depth.
Bagged vs bulk economics
A cubic yard is 27 cubic feet. In 2-cubic-foot bags that's 14 bags (rounding 13.5 up); in 1.5-cubic-foot bags, 18. Once a project crosses roughly 8–12 bags, bulk delivery is usually cheaper per cubic foot and saves a mountain of plastic — but you need a way to move loose material from the pile to the bed. Below that, bags are simpler and cleaner.
Weight matters when you're hauling
Volume tells you how much to buy; weight tells you whether your vehicle can carry it. Mulch is light (roughly 400–1,000 lb per cubic yard), but a single cubic yard of wet soil or gravel can exceed 2,500 lb — beyond the safe payload of many pickups. If you're picking up rather than getting delivery, check the material's weight with the supplier and your vehicle's payload rating.
How to measure your area
Accurate volume starts with an accurate area. Here's the fastest reliable way to measure,
whatever the shape of your bed.
Sketch the bed and break it into simple shapes
Most beds aren't perfect rectangles or circles. Break an irregular area into rectangles, circles, and triangles you can measure separately, then add the results. The calculator handles one rectangle or one circle at a time — run it for each piece and total the cubic yards.
Measure in feet, and measure twice
Use a tape measure or a measuring wheel. For a rectangle, record length and width; for a circle or round bed, measure the diameter straight across the widest point. Measuring twice catches the single most common error — a transposed or misread number.
Decide your depth before you buy
Pick the depth from the recommended-depth chart above (or the depth helper) based on what you're doing — bedding mulch, new lawn topsoil, decorative gravel. Depth is the variable people guess at; settling it up front prevents both shortfalls and the more common over-ordering.
Run the calculator and note both units
Enter your numbers above. Bulk suppliers sell by the cubic yard; bagged products are labeled in cubic feet — having both means you can price either way. The tool also gives the bag count for the common sizes so you can compare bagged against a bulk delivery.
Add a margin and confirm weight if hauling
Add about 5–10% for settling and spillage. If you're transporting it yourself rather than taking delivery, confirm the material's weight per cubic yard with the supplier and check it against your vehicle's payload — soil, sand, and gravel are heavy enough to matter.
Buying bagged or bulk material
Once you know your cubic yards, you can compare a bulk delivery against bagged product at
a local garden center or home-improvement store. Start with whatever is closest and check
delivery fees — they often swing the bagged-vs-bulk decision more than the material price.
Where to buy
Got your numbers? Here's where to pick up what you need:
The terms that show up when you order mulch, soil, or gravel — in plain English.
Cubic yard
The standard unit for selling bulk landscape material — a cube three feet on each side, equal to 27 cubic feet. Spread one inch deep it covers about 324 square feet. "A yard" of mulch or soil always means a cubic yard, never a length.
Cubic foot
A cube one foot on each side. Bagged products are labeled in cubic feet (a 2 cu ft bag of mulch, a 1.5 cu ft bag of soil). There are exactly 27 cubic feet in a cubic yard, which is the conversion that connects bags to bulk.
Depth
How thick the material is spread, measured in inches. Depth is the variable that most changes how much you need, and for mulch around plants it has a recommended range — too shallow won't suppress weeds; too deep can harm roots. See the recommended-depth chart.
Coverage
The area a given amount of material covers at a chosen depth. Coverage and depth trade off: the same cubic yard covers twice the area at half the depth. Garden-center coverage charts are just 324 square feet divided by the depth in inches.
Scoop
An informal unit some suppliers use for loose material loaded by a front-end loader bucket. A "scoop" is not standardized — it can be half a cubic yard, a third, or another fraction depending on the bucket. Always ask how many cubic feet or cubic yards a scoop actually contains before comparing prices.
Bulk (loose) material
Material sold loose by the cubic yard, picked up or delivered in a pile rather than in bags. Usually cheaper per cubic foot than bagged and creates no plastic waste, but you need a truck or delivery and a wheelbarrow to move it.
Bagged material
Material sold in sealed plastic bags labeled by cubic foot. Convenient and clean for small jobs, but more expensive per unit. Common sizes: mulch in 2 cu ft bags; soil in 1.5 and 0.75 cu ft bags; gravel in 0.5 cu ft bags.
Topsoil
Screened upper-layer soil used to build up grade or establish lawns and beds. Heavier than mulch — roughly 1,400–2,000 lb per cubic yard dry, more when wet. Quality varies widely; ask whether it's screened and what it's blended from.
Compost
Decomposed organic matter used to amend soil and add nutrients, rather than as a standalone growing medium. Typically tilled into existing soil at 1–3 inches, or top-dressed thinly on lawns.
Fill dirt
Subsoil with little organic matter, used to fill holes, raise grade, or build up low spots — not for planting. Cheaper than topsoil and used structurally beneath it.
Frequently asked
It depends on the bag size. A cubic yard is 27 cubic feet, so divide 27 by the bag's cubic-foot size. The most common bagged mulch is 2 cubic feet, which gives 27 ÷ 2 = 13.5 bags per cubic yard — round up to 14. For 3 cubic foot bags it's 9 bags per yard; for 1.5 cubic foot bags, 18. Always round up, because partial bags aren't sold. Once you need more than roughly 8–12 bags, bulk (loose) mulch is usually cheaper per cubic foot.
For most landscape beds, university extension services recommend a 2–3 inch layer of organic mulch; Colorado State University Extension cites 3–4 inches for coarser wood and bark mulches. Around trees, Penn State Extension recommends 2–4 inches on well-drained soil and less on poorly drained soil, kept pulled back from the trunk — never piled against the bark in a "volcano." Finely textured mulches should be applied thinner (about 1–2 inches) because they restrict oxygen to the roots. More than about 4 inches can harm plant and tree health.
Approximately 400 to 1,000 pounds per cubic yard, depending heavily on the material and moisture — these are approximate ranges, not exact figures. Dry shredded wood or bark mulch is roughly 400–700 lb per cubic yard; after rain or irrigation it can exceed 800 lb because the fibers hold water. Denser compost-based mulches run higher, around 600–1,000 lb. Weight also varies with wood species and particle size. If a delivery truck's capacity or your vehicle's payload matters, ask your supplier for their specific material's weight.
Use the formula: cubic feet = area in square feet × (depth in inches ÷ 12), then divide by 27 to get cubic yards (there are 27 cubic feet in a cubic yard). Example: a 10 ft × 12 ft bed is 120 sq ft; at 3 inches deep that's 120 × (3 ÷ 12) = 30 cubic feet = 30 ÷ 27 ≈ 1.11 cubic yards. For a circular area, square footage is π × radius² (radius is half the diameter). The calculator at the top does this and shows the steps.
Exactly 27. A cubic yard is a cube three feet on each side, and 3 × 3 × 3 = 27 cubic feet. This is the single most useful conversion in landscaping: bulk materials (mulch, soil, gravel, sand) are sold by the cubic yard, while bagged products are labeled in cubic feet. To convert a yardage to bags, divide 27 by the bag size, then multiply by your number of yards.
These are much heavier than mulch, and all figures are approximate and rise with moisture and compaction. Topsoil is roughly 1,400–2,000 lb per cubic yard when dry and can approach 3,000 lb saturated. Dry sand is roughly 2,600–3,000 lb per cubic yard. Crushed gravel and stone run roughly 2,400–2,900 lb per cubic yard. A single cubic yard of gravel or wet soil can exceed the safe payload of a half-ton pickup — confirm weights with your supplier before hauling it yourself.
A cubic yard (27 cubic feet) spread evenly covers about 324 square feet at 1 inch deep — because 27 ÷ (1 ÷ 12) = 324. So at 2 inches it covers about 162 sq ft, at 3 inches about 108 sq ft, and at 4 inches about 81 sq ft. Coverage is simply 324 divided by the depth in inches. This is the basis for every coverage chart at a garden center, and it assumes the material is spread evenly with no compaction.
It depends on quantity, access, and whether you can move loose material. Bagged is convenient, clean, and easy for small jobs, but costs more per cubic foot and creates plastic waste. Bulk (loose, by-the-cubic-yard) is cheaper per unit and bag-free, but needs a truck or delivery and a wheelbarrow. A common rule of thumb: once a project needs more than roughly 8–12 bags (about a cubic yard), bulk usually wins on price and effort. Below that, bags are simpler. Factor in delivery fees, which often decide it.
Common mistakes
Volume math is reliable, but these four errors consistently turn a correct calculation into
the wrong order — or the right amount applied the wrong way.
Mulch volcanoes against tree trunks
Piling mulch directly against a trunk — the so-called "mulch volcano" — traps moisture against the bark, promotes crown rot, and invites insects. University extension programs are consistent: keep mulch pulled back at least 3 to 6 inches from the trunk, spread in a flat donut, not piled against the bark. Calculating the correct cubic-yard total and then dumping it into a cone at the base still delivers the right amount to the wrong place.
Going too deep with mulch
More mulch does not mean better results. Beyond about 4 inches, organic mulch restricts oxygen to roots and can keep soil waterlogged. The recommended 2 to 3 inch depth is not a minimum — it is the target. Spreading 5 or 6 inches because it "looks better" roughly doubles the material you need and can injure the plants the mulch is meant to protect.
Mixing up bagged cubic feet and bulk cubic yards
Bulk suppliers quote cubic yards; bag labels show cubic feet. One cubic yard equals 27 cubic feet — roughly 14 two-cubic-foot bags. If you calculate "30 cubic feet" and order 30 cubic yards, you'll receive 810 cubic feet of material. The calculator shows both units in parallel precisely to prevent this; if you're writing the number down to call a supplier, make sure you note which unit you're quoting.
Using garden soil where topsoil is needed (and vice versa)
Topsoil and bagged garden soil serve different purposes. Topsoil is screened subsoil used to grade and build up ground level. Bagged garden soil is amended for planting beds. Filling a grading project with bagged garden soil is expensive and structurally unnecessary. Using topsoil alone in a raised bed tends to compact solid within a season. Check which material the project actually needs before entering depth into the calculator.