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Mulch Calculator

Area to cubic yards, bags and coverage

"Mulch Calculator" Calculator

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Mulch: the Formula, the Coverage and What a Yard Weighs

How much mulch a bed needs

Mulch is bought by volume — by the bag or by the yard — so «how much» is a volume question. For a rectangular bed it is one multiplication and one division:

cubic yards = square feet × depth in inches ÷ 324

The 324 is not a rule of thumb. A cubic yard is 3 × 3 × 3 feet = 27 cubic feet; spread one inch deep it becomes a sheet 27 × 12 = 324 square feet across. Divide 324 by the depth you want and you have the coverage of one yard. Nothing in that chain depends on what the mulch is made of, which is why the volume is exact and the weight is only an estimate.

Step by step

  1. Measure the bed in square feet. Width × length for a rectangle; split a border or an island bed into rectangles and add them up.
  2. Choose the depth in inches. Extension services recommend 2–4 inches of organic mulch; 3 inches is the middle of that range and the default here.
  3. Multiply and divide by 324. That is cubic yards. Multiply the square feet by the inches and divide by 12 instead if you want cubic feet, which is what bags are labelled in.
  4. Divide the cubic feet by the bag size. A standard bag is 2 cubic feet, so a cubic yard is 13.5 bags — and part bags always round up.

How much one cubic yard covers

This is the second question the topic asks, and the answer only depends on depth — not on the material:

Depth One cubic yard covers Mulch for 100 square feet Bags Typical use
1 inch324 square feet0.31 cubic yards5 bags a top-up over last year’s mulch
2 inches162 square feet0.62 cubic yards9 bags minimum that suppresses weeds
3 inches108 square feet0.93 cubic yards13 bags recommended depth for most beds
4 inches81 square feet1.23 cubic yards17 bags upper limit for organic mulch
6 inches54 square feet1.85 cubic yards25 bags too deep for plants — paths only

What a cubic yard of mulch weighs

Weight is the second thing people ask about mulch, usually because they are deciding between a delivery and several trips in a car. Here the honest answer is a band, not a figure:

  • Dry bark or wood chips: roughly 400 to 800 lbs per cubic yard — a fifth to two fifths of a ton. A 2 cubic foot bag is therefore around 30 to 60 lbs.
  • Soaked with rain: two to three times that. Mulch is a sponge; a load that fitted in the car dry may be over the axle rating wet.
Why no source is cited here. Density figures for aggregates are published by highway authorities; nobody publishes an authoritative density for garden mulch, because it depends on the species, the chip size, the age of the pile and the weather. So this page prints a typical range with no citation instead of a precise number with a fake one.

Bags or bulk

One cubic yard is 27 cubic feet, so it is 13.5 bags of 2 cubic feet. Bagged mulch is priced per bag and bulk mulch per yard, which is why the two are hard to compare in the aisle: convert both to the same volume first. Bags win on small beds and on anything you have to carry through a house; bulk wins from roughly two cubic yards up, where the delivery charge is spread over enough material to matter.

What people are actually working out

  • Beds and borders: the everyday case — measure the bed, take 3 inches, order.
  • Around trees: a ring, not a volcano. Mulch piled against the trunk keeps the bark wet and invites rot; leave a hand's width of clear ground around the stem.
  • Weed suppression: the depth is doing the work. Under 2 inches light reaches the soil and weeds come through anyway.
  • Playgrounds and paths: deeper than a bed, and a different product — engineered wood fibre rather than bark.
  • Topping up: last year's mulch has not vanished, it has composted down. Measure what is left and add the difference, not the full depth.

Where the formula stops working

  • The bed must be flat and rectangular. Split irregular shapes into rectangles; for a ring around a tree, take the outer circle and subtract the inner one.
  • Deeper is not better. Over 4 inches of organic mulch keeps water and air from the roots, which is the opposite of what mulching is for.
  • Mulch settles and decomposes. A 3 inch layer will not be 3 inches next spring, so plan on topping up rather than on a one-off.
  • The weight is an estimate. Use it to decide whether a load will fit in the car, not to settle a delivery invoice.

Doing it in your head

Remember one number: 324. One cubic yard, one inch deep, covers 324 square feet — so at the recommended 3 inches a yard does about 110 square feet, and 100 square feet is very nearly one yard, or about 13 bags. Most home beds land between half a yard and two yards.

Mulch for common areas

At the recommended depth of 3 inches, in bulk and in bags:

Area Mulch Cubic feet Bags
30 square feet0.28 cubic yards7.5 cubic feet4 bags
50 square feet0.46 cubic yards12.5 cubic feet7 bags
60 square feet0.56 cubic yards15 cubic feet8 bags
80 square feet0.74 cubic yards20 cubic feet10 bags
100 square feet0.93 cubic yards25 cubic feet13 bags
120 square feet1.11 cubic yards30 cubic feet15 bags
150 square feet1.39 cubic yards37.5 cubic feet19 bags
160 square feet1.48 cubic yards40 cubic feet20 bags
200 square feet1.85 cubic yards50 cubic feet25 bags
250 square feet2.31 cubic yards62.5 cubic feet32 bags
300 square feet2.78 cubic yards75 cubic feet38 bags
400 square feet3.7 cubic yards100 cubic feet50 bags
500 square feet4.63 cubic yards125 cubic feet63 bags
600 square feet5.56 cubic yards150 cubic feet75 bags
800 square feet7.41 cubic yards200 cubic feet100 bags
900 square feet8.33 cubic yards225 cubic feet113 bags
1,000 square feet9.26 cubic yards250 cubic feet125 bags
1,200 square feet11.11 cubic yards300 cubic feet150 bags
1,500 square feet13.89 cubic yards375 cubic feet188 bags
2,000 square feet18.52 cubic yards500 cubic feet250 bags
No prices here, on purpose. What a bag or a yard of mulch costs depends on the supplier, the product and the season; we have no data on any of the three, so this page answers volume, bags, coverage and weight and leaves the price to your supplier.

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FAQ

How much mulch do I need?

Multiply the area in square feet by the depth in inches and divide by 324 — that gives cubic yards. A 200 sq ft bed at 3 inches deep is 200 × 3 ÷ 324 = 1.85 cubic yards, which is 50 cubic feet, or 25 bags of 2 cubic feet.

How much does a yard of mulch weigh?

Dry bark or wood chips typically run 400 to 800 pounds per cubic yard, so a yard is roughly a fifth to two fifths of a ton. This is a typical range rather than a measured figure — no authoritative source publishes a single density for mulch — and soaked mulch weighs two to three times as much.

How much area does a yard of mulch cover?

One cubic yard spread 1 inch deep covers 324 square feet. Divide that by your depth: 162 square feet at 2 inches, 108 at 3 inches, 81 at 4 inches, 54 at 6 inches.

How many bags of mulch are in a yard?

A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cubic feet — the standard US bag size. Bagged mulch is priced per bag and bulk mulch per yard, which is why the two are hard to compare directly.

How deep should mulch be?

Extension services recommend 2 to 4 inches of organic mulch; this calculator uses 3 inches, the middle of that range. Deeper is not better: mulch piled against a trunk holds moisture on the bark, and more than 4 inches can keep water and air away from the roots.

How much mulch should I order?

The WSDOT Design Manual advises adding 10 % to a calculated quantity when material is stockpiled, to allow for waste. That figure is for aggregate rather than mulch, but it is the same handling loss, and the result page prints it next to the exact volume. Bagged quantities are rounded up to the next whole bag.