Mulch & Topsoil Calculator

How the mulch estimate works

• Volume = area × depth. We convert with the landscaper's identity: 1 cubic yard covers 324 ft² at 1 inch deep, so cubic yards = area × depth(in) ÷ 324.
• 200 ft² at 3″ = 200 × 3 ÷ 324 = 1.85 cubic yards = 50 ft³ = 25 bags of 2 cu ft.

Mulch is loose fill with no cut waste, so the quantity is exact for your area. A 2–4 inch layer is typical; go thinner for fine mulch and thicker for paths.

What one cubic yard of mulch actually covers

The number 324 is not a rule of thumb, it is arithmetic: 27 cubic feet in a cubic yard × 12 inches in a foot. Spread a yard one inch thick and it covers 324 square feet. Spread it twice as thick and it covers half as much. That single identity drives every figure on this page.

Depth	Sq ft per cubic yard	Sq ft per 2 cu ft bag	Bags per 100 sq ft
1″	324 ft²	24 ft²	5
2″	162 ft²	12 ft²	9
3″ (default)	108 ft²	8 ft²	13
4″	81 ft²	6 ft²	17
5″	65 ft²	4.8 ft²	21
6″	54 ft²	4 ft²	25

Read the third column before you go to the store. A 2 cu ft bag covers only about 8 square feet at the standard 3 inch depth — roughly a 3 ft × 3 ft patch. That is why a bed that looks small still eats a pallet of bags.

How many bags are in a cubic yard?

A cubic yard is 27 cubic feet, so divide by the bag size. You cannot buy half a bag, which is why the "buy" column rounds up.

Bag size	Bags per cubic yard	Bags to buy	Est. price each	Effective cost per cubic yard
2 cu ft	13.5	14	$4.00	$54.00
3 cu ft	9	9	$5.50	$49.50
Bulk, delivered	—	—	—	$40.00 plus a delivery fee

The 3 cu ft bag is the quiet win here: at these estimates it works out to $49.50 per cubic yard against $54.00 for the 2 cu ft bag, and it divides into exactly 9 bags per yard with nothing left over. If your store stocks both, compare on cost per cubic foot rather than cost per bag.

Where bulk delivery actually starts winning

Everyone tells you bulk is cheaper. It is — but by less than you think, and the delivery fee has to be earned back before it means anything. At these estimates a cubic yard in 2 cu ft bags costs $54.00 against $40.00 in bulk, so bulk saves just $14.00 per cubic yard. Divide the delivery fee by that:

Delivery fee	Yards to break even	That is a bed of about
$50	3.6 yd³	386 ft² at 3″
$75	5.4 yd³	579 ft² at 3″
$100	7.1 yd³	771 ft² at 3″

So on a typical $75 drop fee you need roughly 5.4 cubic yards — about 579 square feet of bed — before bulk is genuinely cheaper. Below that you are paying for the truck. Bulk still wins on handling for anything over a few yards, and there is no plastic to dispose of, but do not order a yard-and-a-half delivered and expect to save money.

The calculator above switches its recommendation to bulk at 0.5 cubic yards. That is the point where bulk is worth phoning about — where hauling bags stops being pleasant and a supplier will take the order seriously. It is not the point where bulk is cheaper, because that depends on a delivery fee we cannot know. Treat the widget as "consider bulk" and this table as "bulk actually saves money". We walk through the full comparison in bagged mulch vs bulk delivery.

A worked example: 200 ft² at 3 inches

Every step, with nothing hidden:

1. Area × depth ÷ 324 → 200 × 3 ÷ 324 = 1.85 cubic yards.
2. Cubic feet → 200 × (3 ÷ 12) = 50 ft³.
3. Bags → 50 ÷ 2 = 25 bags of 2 cu ft.
4. Bulk order → suppliers sell to the half yard, so 1.85 rounds up to 2 yd³.

Cost check: $100 in bags against $80 of bulk plus $75 delivery = $155. Bags win this one, and it is not close. Note also that the bulk order rounds up to a clean 2 yards — you pay for the rounding, so bumping the depth slightly to use it up is usually smarter than leaving it on the driveway.

Common bed sizes at 3 inches

Bags and cost are for 2 cu ft bags at $4.00 each; the delivered column is $40 per yard plus a $75 fee.

Bed area	Cubic yards	2 cu ft bags	Est. bags cost	Est. bulk delivered	Cheaper
100 ft²	0.93	13	$52	1 yd³ · $115	Bags
200 ft²	1.85	25	$100	2 yd³ · $155	Bags
300 ft²	2.78	38	$152	3 yd³ · $195	Bags
500 ft²	4.63	63	$252	5 yd³ · $275	Bags
800 ft²	7.41	100	$400	7.5 yd³ · $375	Bulk
1,200 ft²	11.11	150	$600	11.5 yd³ · $535	Bulk

The crossover falls between 500 and 800 ft² — exactly where the 5.4 yard break-even (579 ft²) says it should. If you are near that line, count the trips as well as the dollars: 63 bags is several carloads or a couple of pickup runs, and that is a real cost even if it never shows up on a receipt.

How deep should mulch be?

Two to four inches is the working range for almost everything. Under two inches and weeds come straight through; over four and you start starving roots of air and holding water against stems. Texture decides where in the range you land, because fine material packs tighter than coarse:

Material or situation	Target depth	Coverage per yd³	Why
Fine shredded hardwood, double-ground bark	2″	162 ft²	Fine particles knit together and shed water if you pile them deeper.
Bark nuggets, wood chips, medium bark	3″	108 ft²	The general-purpose default for beds, shrubs and foundation plantings.
Coarse chips on a walking path	4″	81 ft²	Foot traffic compresses and scatters it, so paths start deeper.
Compost used as a top-dress	1″	324 ft²	This is a soil amendment, not a weed barrier. Thin is correct.
Around annuals and shallow-rooted perennials	2″	162 ft²	Deep mulch smothers small crowns and delays spring warm-up.

Topping up vs starting over

Organic mulch is supposed to break down — that is the point of it. What that means in practice is that last year's 3 inch layer is now roughly 1½ to 2 inches of part-composted material that is doing your soil good. You do not need to replace it. You need to make up the difference. Here is a 300 ft² bed at each option:

Top-up depth	Cubic yards	2 cu ft bags	Est. cost in bags
1″	0.93	13	$52
1.5″	1.39	19	$76
2″	1.85	25	$100
3″ (full re-mulch)	2.78	38	$152

A 1 inch refresh on that bed costs $52 against $152 for a full 3 inch layer — a saving of $100, about 66%. Before you order, push a trowel into the bed and measure what is actually left, then buy the difference. If the existing layer is matted or crusted, break it up with a rake first so water and air can get through; that costs nothing and does more for the plants than another inch on top.

Mulch vs topsoil vs compost

All three use the same 324 identity, so the volume math never changes. What changes is the depth you spread them at and — critically for delivery — how much a yard weighs:

Material	Typical depth	Coverage per yd³	Rough weight per yd³	Hauling it yourself
Bark mulch	3″	108 ft²	400–800 lb	2–3 yd fits a half-ton pickup before you run out of bed space
Compost	1″	324 ft²	1,000–1,600 lb	About 1 yd is a sensible pickup load
Screened topsoil	4″	81 ft²	1,800–2,300 lb	Half a yard puts a half-ton pickup at its payload limit

Weight is why the same "one yard" order behaves so differently. A yard of dry bark is a light, bulky load; a yard of wet topsoil can weigh more than a ton and will flatten the springs on a pickup that handled mulch fine last month. If you are hauling rather than paying for delivery, ask the yard what the material weighs that day — it changes with rain. The same weight-versus-volume trap is what makes aggregate ordering tricky, and it is covered in cubic yards to tons and bags.

Do I have to remove the old mulch first?

Usually not. Organic mulch that has broken down is free soil conditioner, and stripping it wastes both the material and your afternoon. Remove it only when the total accumulated depth is past about 4 inches, when it has grown a solid crust that water runs off, or when it is visibly mouldy or sour-smelling. Dyed mulch is the exception people forget: the colour fades long before the wood breaks down, so a bed can look tired while still holding a full layer. Rake it to expose fresh faces before you assume you need more.

How do I measure an irregular bed?

Break it into shapes and add them up. A rectangle is length × width. A circle is 3.14 × radius × radius. A triangle is half the base × the height. Curved borders are best treated as a run of rectangles — measure the width at several points along the bed, average them, and multiply by the length. Pacing works fine for this: a normal adult stride is close to 2½ feet, so 8 paces is about 20 feet. You are estimating loose fill, not cutting sheet goods, so a few per cent either way costs you a fraction of a bag. Enter the total square footage into the calculator above and it does the rest — or check the gravel calculator and concrete calculator if the same bed is getting a stone path or an edging strip. The constants behind all of it are listed in how we calculate, and there is more background in the guides.