Mulch Calculator
With length 30 ft, width 8 ft, depth 3 inch, waste allowance 10 %, mulch comes to 2.44 cu yd — mulch needed. It is reached in 8 steps, the last of which is 66 / 27, and each one is printed on the page with its numbers filled in. The formula is the one published by Penn State Extension, Mulching Landscape Trees, not an approximation fitted to it.
Cubic yards and bags of mulch for a bed, with a waste allowance and a warning when the depth would smother the roots.
Formula and sources checked · How we check
Bed size Length and width, Length 30 ft, Width 8 ft, Mulch texture Coarse — bark nuggets, wood chips
2.44 cu yd
Mulch needed for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.
It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.
- Bed area
1 * (30 * 8) + 0 * 240240 sq ft- Volume
240 * 3 / 1260 cu ft- Volume with waste
60 * (1 + 10 / 100)66 cu ft- Cubic yards
66 / 272.444 cu yd- Bags to buy
ceil(66 / 2)33 bags- Depth over the recommended maximum
max(0, 3 - (4 * 1 + 2 * 0))0 in- Weight if dry
2.4444444 * 243594 lb- Weight if green or wet
2.4444444 * 4731,156.222 lb
Several at once
A job is rarely one of anything. Work out the first, add it, change the figures and add the next — the list keeps what each line was, and totals them.
Worked example
A 30 by 8 ft bed at 3 inches is 60 cubic feet, 66 with waste, which is 2.44 cubic yards or 33 two-cubic-foot bags. Bulk delivery is usually cheaper past about 2 yards, or roughly 27 bags.
How to work it out yourself
- 1.Measure the bed in feet. Curved beds are close enough if you take an average width and multiply by the length.
- 2.Pick the depth. Three inches is the working figure for bark and chips; fine shredded mulch and compost pack down and should go on thinner.
- 3.Multiply area by depth in feet, then divide by 27 for cubic yards. Bagged mulch is sold in cubic feet, so the bag count comes from the same number before dividing.
- 4.Keep mulch off the trunk. Three to five inches of clearance for a young tree, eight to ten for a mature one.
How far one cubic yard goes
A cubic yard is 27 cubic feet. Spread one inch deep it covers 324 square feet, and every other depth is that figure divided by the depth in inches — which is the whole table in one sentence.
| Depth | Square feet | Square yards |
|---|---|---|
| 1 in | 324 | 36.0 |
| 2 in | 162 | 18.0 |
| 3 in | 108 | 12.0 |
| 4 in | 81 | 9.0 |
| 6 in | 54 | 6.0 |
| 8 in | 41 | 4.5 |
| 10 in | 32 | 3.6 |
| 12 in | 27 | 3.0 |
Cubic yards for a given area
| Area | 1 in | 2 in | 3 in | 4 in | 6 in | 8 in | 10 in | 12 in |
|---|---|---|---|---|---|---|---|---|
| 100 sq ft | 0.31 | 0.62 | 0.93 | 1.23 | 1.85 | 2.47 | 3.09 | 3.70 |
| 200 sq ft | 0.62 | 1.23 | 1.85 | 2.47 | 3.70 | 4.94 | 6.17 | 7.41 |
| 500 sq ft | 1.54 | 3.09 | 4.63 | 6.17 | 9.26 | 12.35 | 15.43 | 18.52 |
| 1,000 sq ft | 3.09 | 6.17 | 9.26 | 12.35 | 18.52 | 24.69 | 30.86 | 37.04 |
Suppliers deliver in whole or half yards, so round up — a truck will not bring 2.37.
Bags to the cubic yard
| Bag | Holds | Bags per yard |
|---|---|---|
| Mulch, 2 cu ft bag | 2 cu ft | 14 |
| Mulch, 3 cu ft bag | 3 cu ft | 9 |
| Topsoil or compost, 1 cu ft bag | 1 cu ft | 27 |
| Concrete mix, 80 lb bag | 0.6 cu ft | 45 |
| Concrete mix, 60 lb bag | 0.45 cu ft | 60 |
| Concrete mix, 40 lb bag | 0.3 cu ft | 90 |
Concrete is sold by weight and the yield is printed on the bag, which is why it takes 45 of the 80 lb bags to make a yard rather than the dozen people expect. Past about ten bags, ready-mix is cheaper and far less work.
Depth by use
| Use | Depth | Why |
|---|---|---|
| Mulch, established beds | 2–3 in | Deeper than 3 in holds water against stems and starves roots of air. |
| Mulch, new beds over bare soil | 3–4 in | The extra inch is what suppresses weeds for a season. |
| Topsoil over an existing lawn | 0.25–0.5 in | Any more and the grass underneath is smothered rather than fed. |
| Topsoil for a new lawn | 4–6 in | Roots need the depth once, at the start; it cannot be added later. |
| Gravel walkway | 2–4 in | Over a compacted base, not over soil. |
| Gravel driveway, surface course | 3–4 in | Over 6 to 8 in of compacted base. |
| Gravel driveway, full build | 8–12 in | Base and surface together, laid and compacted in layers. |
| Concrete patio or walkway | 4 in | Four inches is the ordinary residential slab. Follow the specification for anything carrying a vehicle. |
How much extra to order
| Reason | Add | Note |
|---|---|---|
| Compaction, crushed stone | 20% | Six inches loose settles to about five. Order for the finished depth. |
| Settling, mulch and soil | 10–15% | Organic material shrinks as it breaks down over the first season. |
| Spillage and uneven ground | 5–10% | A hole is never the rectangle it was measured as. |
| Concrete, sub-base variation | 5–10% | A slab poured half an inch deep over 200 sq ft is a third of a yard nobody ordered. |
The formula
- Bed area
1 * (30 * 8) + 0 * 240 - Volume
240 * 3 / 12 - Volume with waste
60 * (1 + 10 / 100) - Cubic yards
66 / 27 - Bags to buy
ceil(66 / 2) - Depth over the recommended maximum
max(0, 3 - (4 * 1 + 2 * 0)) - Weight if dry
2.4444444 * 243 - Weight if green or wet
2.4444444 * 473
Source: Penn State Extension, Mulching Landscape Trees — 2 to 4 inches of organic mulch, less for fine textures, NIST Handbook 130, Uniform Method of Sale §2.18.2 — mulch is sold by volume, not weight, US EPA, Volume-to-Weight Conversion Factors, April 2016 — wood chips, dry and green
Questions people actually ask
- How deep should mulch be?
- Two to four inches for bark or chips, and one to two for finely shredded mulch or compost, which packs down and holds water against the roots. Penn State Extension caps organic mulch at four inches; past that the layer stays wet, roots grow up into it, and the tree is worse off than with no mulch at all. This calculator flags the depth when it goes over the maximum for the texture you picked.
- How many bags is a cubic yard?
- Thirteen and a half two-cubic-foot bags, or nine three-cubic-foot bags. Bulk delivery usually beats bags somewhere around two yards once the delivery fee is spread over the load, which is about 27 of the small bags.
- How much does a yard of mulch weigh?
- Roughly 240 lb dry and up to 475 lb green or rain-soaked, using the EPA wood-chip figures. That range is about the water in it, not about the product: the same mulch weighs twice as much the day after a storm, which is what decides whether it fits in a pickup.
- Is mulch sold by weight or volume?
- By volume. NIST Handbook 130 requires mulch to be sold in cubic yards, cubic feet, cubic meters or liters, so a price quoted per ton is not a lawful method of sale for it. The weight figures here are for working out whether the load fits in your vehicle.
Related
- Gravel & Aggregate CalculatorCubic yards and tons of gravel, sand, limestone or topsoil for an area at a given depth.
- Square Footage CalculatorSquare footage of a room, wall, border, gable end, ring or triangle from feet-and-inches measurements, with a waste factor and the cost.
- Cubic Yard CalculatorCubic yards for any footprint and depth, with a waste allowance and the weight of the debris if you are hauling it away.
- Material Weight CalculatorWhat a volume of gravel, sand, topsoil or mulch weighs, and what a weight takes up, so tons quoted by a supplier can be checked against yards measured on site.
- Topsoil CalculatorHow much topsoil a bed or a lawn needs, in cubic yards and in bags, with the weight — the number that decides truck or car boot.
- Sod CalculatorRolls and pallets of sod for a lawn, from the area and the roll size the farm cuts, with the waste a shaped lawn actually needs.
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