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Mulch Calculator

Measure your beds and get the cubic yards, bag count and — for gravel and soil — the delivery weight in tons.

Where are you?

AWG, NEC, 120/240 V, miles and gallons — we remember this on every calculator.

How are you measuring?
Your beds

Tick each bed you are covering and enter its length and width. Add rows for as many as you have — the totals add up across all of them.

What are you spreading?

Material changes the bag size it is sold in, and whether bulk deliveries are quoted by weight.

Depth

Mulch wants 3 inches — 2 does not suppress weeds and 5 suffocates roots. New topsoil for a bed wants 6, gravel paths 4.

Your result

Wood or bark mulch needed

0.74 cu yd

In cubic metres
0.57 m³
In cubic feet
20 cu ft
Bags (2 cu ft)
10
Area covered
80 sq ft
Depth
3 in
Delivery weight
Sold by volume

🪿 The goose says: You need about 0.74 cubic yards of wood or bark mulch — that is 10 bags, or an easy load of bags.

  • Under about 2 cubic yards, bags usually win once you count the delivery fee. 10 bags fits in most cars in two trips.
  • Keep mulch a couple of inches clear of trunks and stems. Piling it against bark — the "mulch volcano" — rots the trunk and is one of the most common ways homeowners kill young trees.

How this mulch calculator works

Bulk landscape materials are sold by the cubic yard, and a cubic yard is bigger than almost everyone pictures: 27 cubic feet, enough to cover 108 square feet at three inches deep. Getting from a bed measurement to that unit is the whole calculation.

The shortcut every landscaper uses is the number 324. Multiply your square footage by the depth in inches, divide by 324, and you have cubic yards. That 324 is just 12 inches per foot multiplied by 27 cubic feet per yard, folded into one constant so you never have to convert twice.

Bags are then a straight division, but bag sizes differ by material — mulch comes in 2 cubic foot bags, topsoil in 0.75, gravel in 0.5. That is why forty bags of gravel is far less material than forty bags of mulch.

  1. Step 1 Total the area area = Σ (length × width), or π × (diameter ÷ 2)² for a round bed
  2. Step 2 Convert to cubic yards cubic_yards = area_sqft × depth_inches ÷ 324 324 = 12 × 27, folding both conversions into one step.
  3. Step 3 Convert to bags bags = ceil(cubic_yards × 27 ÷ bag_size_cuft) Mulch bags are 2 cu ft, topsoil 0.75, gravel 0.5.
  4. Step 4 Convert to delivery weight tons = cubic_yards × density Gravel ≈ 1.4 tons/yd³, topsoil ≈ 1.1, sand ≈ 1.35. Mulch is sold by volume only.

Example: a 20 × 4 ft bed is 80 square feet. At 3 inches deep that is 80 × 3 ÷ 324 = 0.74 cubic yards, which is 20 cubic feet, or 10 bags of mulch.

Assumptions & caveats

Everything this calculator quietly assumes on your behalf. If one of these does not match your situation, the answer will be off.

  • Volumes assume an even depth across a flat bed. Sloped or uneven ground needs more material at the low end, and mounded beds need noticeably more.
  • Bag sizes are the common US retail figures: 2 cubic feet for mulch, 1 for compost, 0.75 for topsoil, 0.5 for gravel and sand. Check your supplier — bag sizes do vary.
  • Bulk weights are approximate and change with moisture: gravel around 1.4 tons per cubic yard, topsoil 1.1, sand 1.35. Wet material can be 15% heavier, which matters if your delivery is priced by weight.
  • Mulch and compost settle. Fresh wood mulch compresses roughly 10–15% in the first few weeks, so a bed spread to exactly 3 inches will read closer to 2.5 after a month.
  • No allowance is made for the space plants occupy. A densely planted bed needs perhaps 10% less than the bare area suggests.
  • Rubber mulch and stone do not decompose and do not need annual topping up. Organic mulch does — budget for about a third of this volume each following year.
  • Delivery minimums are common. Many suppliers will not deliver under 3 cubic yards, or charge the same fee regardless, which changes the bags-versus-bulk maths.

Frequently asked questions

How much mulch do I need?

Multiply your bed area in square feet by the depth in inches, then divide by 324 for cubic yards. A 20 × 4 foot bed at 3 inches deep needs 0.74 cubic yards, which is 10 standard bags. Most home beds land between half a yard and three yards.

How many bags of mulch are in a cubic yard?

Thirteen and a half bags at the standard 2 cubic foot size, because a cubic yard is 27 cubic feet. Suppliers usually round this to 14. For topsoil in 0.75 cubic foot bags it is 36 bags per yard, which is when bulk delivery starts to look obvious.

How deep should mulch be?

Three inches for established beds. Two inches lets light through and weeds come up; more than four holds moisture against stems and cuts oxygen to the roots. Around trees, keep the same three inches but pull it back a few inches from the trunk itself.

How much area does a cubic yard of mulch cover?

About 108 square feet at 3 inches deep, 162 square feet at 2 inches, or 81 square feet at 4 inches. The quick version most landscapers use is "a yard does about 100 square feet", which is close enough for ordering.

Is bulk mulch cheaper than bags?

Per cubic yard, yes — usually less than half the price, sometimes a third. The break-even is around two to three cubic yards once you add the delivery fee, and bulk also saves you dozens of plastic bags and several car trips. Below two yards, bags generally win.

How much does a cubic yard of gravel weigh?

About 1.4 tons, or 2,800 pounds, for typical crushed stone — enough to overload a half-ton pickup on its own. Topsoil is around 1.1 tons per yard and sand about 1.35. This is why gravel is delivered by weight rather than volume.

Do I need landscape fabric under mulch?

Under gravel, yes — it stops stone working down into the soil. Under organic mulch, generally no: mulch is supposed to break down into the soil, and fabric prevents that while eventually filling with soil on top and growing weeds anyway. Save it for stone.

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