Mulch Calculator

Turn bed area and mulch depth into cubic feet, cubic yards, and a count of standard 2 cu ft bags — with the bulk figure alongside so you can price bags against a delivered yard.

Bed area and depth

Example: 200 sq ft of beds at 3 in deep with 5% cushion → 27 bags.

A coverage estimate for buying mulch — grading, drainage, and anything code-adjacent in the landscape belongs with a qualified professional.

Bags are just cubic feet in plastic

cu ft = area × (depth in ÷ 12), and bags = ceil(cu ft ÷ 2) — the bag division is pure arithmetic on the labeled 2 cu ft retail size. The worked bed: 200 sq ft at ¼ ft = 50 cu ft (1.85 cu yd). With 5% extra that is 52.5 cu ft, or 27 bags with 1.5 cu ft left in the last one — equivalently 1.94 cu yd if a yard delivers in bulk. All computed by the engine at build time.

That single bag size is the only coverage figure this page depends on, and it is a packaging convention rather than a measured property of mulch. The guide Coverage figures and where they come from explains how every coverage and yield figure on this site is sourced, labeled, and pinned by a test; the rest of this page explains what the mulch engine does with this one.

The five stages, in order

Every estimator on the site runs the pipeline documented on the methodology page. For mulch the stages look like this, with the worked bed carried through each one:

Geometry. The bed area in square feet is multiplied by the depth converted to feet (inches ÷ 12). That is cubic feet; dividing by 27 gives cubic yards. Both factors are definitions, not measurements. The worked bed's 50 cu ft and 1.85 cu yd come from this stage alone.
Coverage. One retail bag holds 2 cu ft, so the cubic feet are divided by 2 to express the need in bags. There is no coverage table to consult and no area-per-bag figure to look up: a bag of mulch covers whatever area its volume spreads over at the depth you chose.
Waste. The cushion percentage is applied to the volume as cu ft × (1 + cushion ÷ 100). At the default 5% the worked bed grows from 50 to 52.5 cu ft. The cushion is applied to the quantity before any rounding, so it is counted exactly once.
Round-up. The cushioned volume is divided by the bag size and rounded up to a whole bag: 52.5 ÷ 2 = 26.25, which becomes 27 bags. The part of the last bag you did not need — 1.5 cu ft here — is reported as spare. This is the only rounding anywhere in the chain; every intermediate value keeps full precision and is rounded only for display.
User price. If you type a price per bag, the cost is that price times the bag count. Leave the field blank and no cost line appears. The tool never supplies, averages, or guesses a price of its own — every cost figure on this site comes from the number you enter.

What each input does

Bed area is the footprint the mulch will cover, in square feet (or square meters in metric mode). The engine takes one number and does not care what shape produced it, so an L-shaped bed, a ring around a tree, or a dozen separate beds are all handled the same way: total the areas first, then enter the sum. The square footage calculator adds rectangles, triangles, and circles for exactly this purpose.

Depth is entered in inches (centimeters in metric mode), and it is the input that moves the total most. Area is usually measured once and measured well; depth is a choice, and every extra inch adds the same volume again as the first inch did. Because the geometry is linear in depth, doubling the depth doubles the bags exactly — before rounding — and halving it halves them. When a bag count looks wrong, the depth field is the first place to look, and the inches-versus-feet mistake below is the specific error to rule out.

Extra cushion is the waste percentage. Its default of 5% is a trade convention for bulk aggregate and mulch — not a manufacturer figure, and not a measured average — and it is fully adjustable. The convention exists because a spread depth is never perfectly uniform: edges get feathered, low spots take more, and some material stays in the wheelbarrow. Set it to zero if you want the pure geometry, or raise it for a bed you know will be hard to spread evenly.

Price per bag is optional and comes only from you. It multiplies the rounded bag count, so the cost line already includes the spare in the last bag.

Worked examples

Every figure below is computed by the mulch engine when the page is built, from the inputs shown, with the default 5% cushion unless the row says otherwise. The metric row is converted to square feet and inches with exact factors before the engine runs, exactly as the form does it, and converted back for display.

Bed	Area	Depth	Cushion	Net cu ft	Net cu yd	With cushion (cu ft)	Bags	Spare (cu ft)
Garden bed (house example)	200 sq ft	3 in	5%	50	1.85	52.5	27	1.5
Border strip	48 sq ft	2 in	5%	8	0.3	8.4	5	1.6
Top-up over old mulch	350 sq ft	2 in	5%	58.33	2.16	61.25	31	0.75
Large refresh	1,200 sq ft	4 in	5%	400	14.81	420	210	0
Exact fit, no cushion	96 sq ft	3 in	0%	24	0.89	24	12	0
Exact fit, default cushion	96 sq ft	3 in	5%	24	0.89	25.2	13	0.8
Sloped bed, raised cushion	500 sq ft	3 in	10%	125	4.63	137.5	69	0.5
Metric bed	18 m²	8 cm	5%	50.85	1.88	53.4	27	0.6

A border strip along a fence

A strip 12 ft long and 4 ft wide is 48 sq ft — here the area is produced by the geometry engine rather than typed, the way the square footage tool would supply it. At 2 in the strip needs 8 cu ft (0.296 cu yd). The 5% cushion lifts that to 8.4 cu ft, and dividing by the 2 cu ft bag gives 5 bags with 1.6 cu ft spare. A job this small is a bag job: the bulk figure of 0.31 cu yd is printed, but it is a fraction of a yard.

Topping up over last year's mulch

A 350 sq ft bed still holds about 1 in of old mulch and the target is 3 in. The right entry is the difference, 2 in, which gives 58.33 cu ft net and 31 bags after the cushion, with 0.75 cu ft spare. Entering the full 3 in instead would compute 87.5 cu ft and 46 bags — 15 bags more than the bed can absorb. The engine cannot see what is already on the ground; the subtraction is yours to do before you type.

A large refresh where bulk wins

1,200 sq ft of beds at 4 in is 400 cu ft, or 14.81 cu yd, before the cushion. With 5% extra the volume is 420 cu ft — 210 bags, or 15.56 cu yd delivered loose. The tool prints both because the decision is yours: the bag count tells you what a cart-and-car approach involves, and the cubic-yard figure is what a landscape yard needs to hear. Multiply the bag count by your per-bag price and set it against a delivered-yard quote to compare.

An exact fit, and what the cushion does to it

96 sq ft at 3 in is 24 cu ft, which divides into the 2 cu ft bag with nothing left over: with the cushion set to 0% the result is exactly 12 bags and 0 cu ft spare. The engine recognizes an exact fit as an exact fit — a volume that lands on a bag boundary does not buy a phantom bag because of floating-point noise. Restore the default 5% and the cushioned volume becomes 25.2 cu ft, which crosses the next boundary and rounds up to 13 bags with 0.8 cu ft spare. That one extra bag is the cushion doing its job, and the spare line shows you how much of it the rounding, rather than the percentage, added.

A sloped bed with a raised cushion

If a 500 sq ft bed on a slope is hard to spread evenly, raising the cushion to 10% is how you tell the engine so. The net volume at 3 in is 125 cu ft; the cushion adds 12.5 cu ft to reach 137.5 cu ft, which is 69 bags (5.09 cu yd bulk) with 0.5 cu ft spare. Nothing else in the chain changes: the cushion is a single flat percentage on the volume, and the tool has no opinion about what percentage a given bed deserves.

A metric bed: 18 m² at 8 cm

In metric mode the form converts 18 m² to 193.75 sq ft and 8 cm to 3.15 in using the exact definitions of the foot and the inch, then runs the identical engine. The net volume is 50.85 cu ft, presented back as 1.44 m³ (1,440 L) — which is what 18 m² × 8 cm comes to directly, because the conversions are exact in both directions. With the 5% cushion the volume is 1.512 m³ (1,512 L), and the bag line reads 27 bags of the US 2 cu ft size, with 17.1 L spare. The bag stays a US package in metric mode; if your bags are labeled in liters, divide the liter figure by your bag's volume.

Reading the result

The result box leads with the bag count because that is the number most people came for. Under it, the net volume line is the pure geometry in cubic feet and cubic yards — the figure to rescale if your bags are a different size, and the figure to carry into another tool. The with extra line is the cushioned volume, shown in cubic feet and again in cubic yards as the bulk quantity you would order loose. The spare line is the difference between the bags you buy and the cushioned volume: it is what the round-up added, not what the cushion added, and it is always less than one bag. In metric mode the same four lines lead with cubic meters and liters, and the bag count is unchanged. A cost line appears only when you entered a price, and it prices the rounded bag count, spare included.

The depth typo that multiplies the order by 12

Depth goes in as inches; area goes in as square feet. Entering the worked bed's 3 in depth as 3 feet — which the engine reads as 36 in — computes 600 cu ft instead of 50, a volume 12 times too large, and the bag count balloons from 27 to 315. The engine cannot flag this, because a three-foot depth is a valid number: it is the geometry of a pile, not a bed, but the arithmetic is the same. If a bag count is wildly out of scale with the bed you measured, check the depth field before anything else. The mirror-image slip — measuring a depth in feet and typing that number into the inches box — under-buys by the same factor.

Where the model stops

The engine computes the volume of a flat layer at a uniform depth over the area you gave it, cushions that volume by one flat percentage, and divides by one bag size. Everything outside that sentence is left out on purpose. It does not know how much mulch is already on the bed, so the top-up subtraction is yours. It does not model settling, decomposition, or compaction over a season, so it estimates the day you spread, not the depth you will measure next year. It does not model the extra material that feathered edges, tree rings, and slopes consume beyond the cushion you set. It assumes every bag holds its labeled volume; how full a bag actually is, and whether its contents were measured loose or compressed, are the packager's business. It does not know your supplier's minimum delivery or how a bulk load is measured, and it has no view on which mulch to use, how deep to lay it for a given planting, or what should happen at the base of a trunk. Those are horticultural and grading judgments — the scope hint under the form says where they belong.

The constants this page uses

2 cu ft per bag — a packaging convention, not a material property, recorded in the site's materials data as the common big-box retail size. Other sizes exist, and the rescale is plain arithmetic on the printed cubic feet.
5% default cushion — a trade convention for bulk aggregate and mulch, labeled as such in the materials data; adjustable in the form, including down to zero.
12 inches per foot and 27 cubic feet per cubic yard — definitions.
Metric factors — 2.54 cm per inch, 0.09290304 m² per square foot, 0.028316846592 m³ per cubic foot, and 1000 liters per cubic meter — all exact by the international definitions of the inch and the foot.

Nothing else on this page is a sourced figure: there is no coverage-per-bag table, no area-per-yard rule of thumb, and no density, because mulch is sold by volume and the engine never needs a weight. How the site sources, labels, and tests the figures it does use is the subject of Coverage figures and where they come from; the guides index covers the other concepts — cubic yards, waste factors, bag yields — in the same way.

The square footage calculator totals irregular beds before you come here. The topsoil calculator and gravel calculator run the same area-times-depth geometry for materials sold by the yard or the ton, and the sod calculator covers the lawn next to the bed. For a volume in any other shape, the volume calculator returns cubic feet you can carry back into the bag arithmetic, and the construction unit converter moves any figure between cubic feet, cubic yards, cubic meters, and liters.

Frequently asked questions

How deep should mulch go?

Two to four inches is the range most landscape guides work in — enough to suppress weeds and hold moisture without smothering roots. Depth is the biggest lever on the total, so if the bag count surprises you, revisit the depth before anything else.

Bags or a bulk delivery?

The tool shows both figures. One cubic yard is 27 cu ft, so it holds 13.5 of the 2 cu ft bags — small beds favor bags you can carry, big refreshes favor a bulk drop. Compare your per-bag price times the count against a yard delivered.

My bags are 1.5 or 3 cu ft, not 2 — is the count wrong for me?

The count shown assumes the labeled 2 cu ft retail bag. For other sizes, take the cubic-feet figure from the result and divide by your bag volume (the conversion is plain arithmetic, and the exact cubic feet are printed for that reason).

Should I clear the old mulch first?

Usually you top up rather than replace: measure the existing depth, subtract it from your target, and enter only the difference. Entering the full target depth over a bed that still holds an inch of old mulch is the common over-buy.

Why does the tool round up to whole bags instead of showing a decimal?

Because a store sells whole bags. The cushioned volume is divided by 2 cu ft and rounded up once, at the very end, and the fraction of the last bag you did not need is printed as spare. Rounding earlier — say, rounding the cubic feet before dividing — would sometimes buy a bag that the geometry never asked for.

Why is the cushion applied to the volume and not to the bag count?

Adding a percentage to a bag count that has already been rounded up would pad the order twice: once by the round-up, once by the cushion. The engine applies the cushion to the cubic feet first, then rounds, so the margin is counted exactly once and the spare line shows what the rounding alone added.

How do I measure a curved or L-shaped bed?

Break it into rectangles, triangles, and circle segments, add them up in the square footage calculator, and enter the total here. The mulch engine takes one area figure and does not care what shape produced it; the only thing it needs is an honest square-foot total.

Does switching to metric change the arithmetic?

No. Square meters are converted to square feet and centimeters to inches with exact definitional factors before the engine runs, and the cubic feet are converted back to cubic meters and liters for display. The bag count is identical in both modes because the bag is still the same US 2 cu ft package.

Your measurements stay in your browser — nothing is uploaded. The estimation chain behind every tool here is described on the methodology page.