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Landscaping

Mulch Calculator

By Nick Major · Founder, Calculator Campus Last updated July 19, 2026

The mulch calculator works out how much mulch to buy for a bed as BOTH cubic yards for a bulk delivery AND the number of bags for the store, at a depth you choose. Enter a rectangle's length and width (or switch to a round bed, a ring around a tree, or several beds) and a depth, and the cubic yards and bag count come back together. A reverse mode turns an amount you already have into the area it covers, an optional pricing panel compares bulk against bagged, and a rubber-playground mode sizes loose-fill by equipment fall height.

Buy Buy about 0.93 cu yd — or 13 bags at 2 cu ft

Start with a rectangle and a depth to get cubic yards and bag count together — tap a depth preset if you are unsure. Switch the shape for a round bed, a ring around a tree, or multiple beds; switch the mode to find the area an amount you already have will cover, or to size rubber playground mulch by fall height. Open options for a waste allowance or optional bulk-vs-bagged pricing.

What do you want to do?

Default: enter a bed's size and depth to get cubic yards + bag count. Reverse: enter mulch you already have (yards or bags) to get the area it covers. Rubber playground: depth is set by equipment fall height (volume only).

Rectangle is the default. Round bed, ring-around-a-tree, and multiple beds are one click away. Triangle and trapezoid are lower-demand shapes kept at the end of the list.
Bed length in feet. For 'Multiple beds' this is the length of the first bed.
Bed width in feet. For 'Multiple beds' this is the width of the first bed.
For a round bed: the distance straight across the circle, in feet. Area = π × (diameter ÷ 2)².
For a mulch ring around a tree: distance from the trunk centre to the outside edge of the mulched circle, in feet.
Radius of the bare gap kept around the trunk (keep mulch ~2-3 in off the bark). Must be smaller than the outer radius. Ring area = π × (outer² − inner²).
How deep to spread the mulch, in inches. Iowa State Extension recommends 2-4 in for organic mulch; 3 in is a good default for a new bed, 2 in to refresh. Use the depth presets to fill this in one click.
For playgrounds, loose-fill depth is set by how far a child could fall from the equipment. This sets the mulch depth. Confirm the required depth for your specific equipment against CPSC guidance — this preset is a starting point, not a tested safety guarantee.
Retail mulch bag size. 2 cu ft is the most common. This drives the bag count and the bags-per-cubic-yard figure (27 ÷ bag size).
Choose whether you know the amount of mulch in cubic yards (bulk) or in bags.
How many cubic yards of mulch you have or plan to buy. The tool returns the area it covers at your chosen depth.
How many bags you have. Coverage uses the bag size selected above. Answers 'how much will N bags of mulch cover?'
Advanced options
Optional second bed. Leave blank if you only have one bed.
Width of the optional second bed.
Optional third bed. Leave blank if not needed.
Width of the optional third bed.
Base of the triangular bed, in feet. Area = 0.5 × base × height.
Perpendicular height of the triangular bed, in feet.
One parallel side of the trapezoid, in feet. Area = ((A + B) ÷ 2) × height.
The other parallel side of the trapezoid, in feet.
Perpendicular distance between the two parallel sides, in feet.
Optional extra for settling and spillage. A common landscaping allowance is 5-10%. Defaults to 0 so bulk buyers get the true volume; it is never applied silently.
Optional. Enter your local bulk delivered price to compare bulk vs bagged. Leave blank to keep pricing off.
Optional. Enter the in-store price of one bag (at the bag size selected above) to compare bulk vs bagged.
Buy Buy about 0.93 cu yd — or 13 bags at 2 cu ft
Cubic yards (bulk order) 0.93 cu yd
Bags needed 13 bags at 2 cu ft
Cubic feet 25 cu ft
Bed area (sq ft) 100 sq ft
Assumptions Depth 3 in · Bag 2 cu ft · Waste 0%
Cheaper option —
Show calculation details
Bags per cubic yard 13.5 bags per cubic yard at 2 cu ft
Bulk cost —
Bagged cost —
Notes None

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How much mulch to order

The number you buy on is the cubic yards for a bulk delivery or the bag count for the store — the same job either way. The sections below walk the decision from measuring the bed to picking a depth to reading yards versus bags, and cover the two mistakes that cost the most: guessing the depth and piling mulch against a trunk.

Depth is make-or-break

Depth doubles the order when you double it, so it is the input worth measuring. Organic mulch is usually 2-4 in deep — tap the 3 in preset for a new bed or 2 in to refresh an existing one.

Yards and bags together

Cubic yards (for bulk delivery) and bag count (for the store) come back side by side, so you can order whichever way is cheaper without converting by hand. A 2 cu ft bag is 13.5 bags per cubic yard.

Measure odd beds in pieces

Break a curved or L-shaped bed into rectangles and circles, add the areas, or use the multiple-beds shape. A ring around a tree uses the trunk gap as its inner radius so mulch stays off the bark.

Bulk versus bagged

Bagged mulch suits small beds, but past about a cubic yard — roughly 13-14 bags at 2 cu ft — bulk delivery is usually cheaper than hauling and opening bags. The optional pricing panel compares the two.

Worked example: a 10 × 10 ft bed at 3 in

Take a 10 × 10 ft bed at a 3 in depth. The area is 10 × 10 = 100 sq ft; the volume is 100 × 3 ÷ 12 = 25 cubic feet, which is 25 ÷ 27 = 0.93 cubic yards — the number for a bulk delivery. At the common 2 cu ft bag that is 25 ÷ 2 = 12.5, rounded up to 13 bags, because you cannot buy a partial bag. The bags-per-yard figure of 13.5 (27 ÷ 2) is a quick sanity check: just under a cubic yard should be just under 14 bags, which it is. Drop the depth to 2 in to refresh instead and the same bed needs about 0.62 cubic yards or 9 bags; a 3 cu ft bag would cut the count to 9 at the 3 in depth. This is exactly why the tool shows yards and bags together.

Mulch coverage per cubic yard by depth

One cubic yard is 27 cubic feet, so it spreads over 324 ÷ depth(in) square feet — the same rule the calculator uses. Deeper mulch covers less ground, which is why depth is the input worth getting right.

DepthArea 1 cubic yard covers
1 in324 sq ft
2 in162 sq ft
3 in108 sq ft
4 in81 sq ft

Coverage per cubic yard is definitional (324 ÷ depth in inches). Organic mulch is usually spread 2-4 in deep (Iowa State Extension), so a single cubic yard typically covers about 80-160 sq ft.

Bags per cubic yard and coverage per bag

Bag count depends on the bag's SIZE, not its weight: bags per cubic yard is 27 ÷ bag size in cubic feet. The 2 cu ft bag is the most common retail size, giving 13.5 bags per cubic yard. Coverage per bag is the same 324 ÷ depth rule scaled to one bag.

Bag sizeBags per cubic yardCoverage per bag at 2 inCoverage per bag at 3 in
1.5 cu ft189 sq ft6 sq ft
2 cu ft (most common)13.512 sq ft8 sq ft
3 cu ft918 sq ft12 sq ft

Bags per cubic yard = 27 ÷ bag size; coverage per bag = bag size × 12 ÷ depth(in). Bag counts round up because you cannot buy a partial bag, and past about a cubic yard (roughly 13-14 bags at 2 cu ft) bulk delivery usually beats hauling bags.

What depth should the mulch be?

Depth drives the whole estimate, and too shallow a guess is the usual reason a bed looks thin or weeds push through. Iowa State Extension recommends 2 to 4 inches of organic mulch, with finer material (like shredded bark or grass clippings) on the lower end and coarser material (like wood chips) on the higher end. A practical rule: 3 in for a new bed, 2 in to refresh an existing one that still has some mulch, and up to 4 in for coarse mulch or heavier weed suppression. The depth presets fill these in one tap and stay editable. Going much past 4 in wastes mulch and can starve roots of air and water, so the tool flags a depth over 6 in as unusual.

Cubic yards, bags, and how they relate

Suppliers sell mulch two ways, so the calculator returns both. Cubic yards is the raw volume (area × depth ÷ 27) and the unit a bulk yard delivers in. Bags is the count for a store run, and it is keyed to the bag's SIZE, not its weight: a 2 cu ft bag is 27 ÷ 2 = 13.5 bags per cubic yard, a 3 cu ft bag is 9, and a 1.5 cu ft bag is 18. A bag spec is cubic feet, not the square feet it covers, and the count always rounds up. Knowing that 13.5 bags make a cubic yard is the fastest way to sanity-check any mulch estimate — and to see the moment bulk delivery becomes the cheaper buy. Reverse mode flips the question: enter an amount you already have and it returns the area it covers at your chosen depth.

Measuring beds, tree rings, and the mulch-volcano mistake

Rectangular beds are just length × width. For a round bed, enter the diameter and the tool uses π × (diameter ÷ 2)². For a ring around a tree, enter the outer radius of the mulched circle and the trunk gap you want to keep bare — the ring area subtracts the gap so you never over-order. That trunk gap matters: piling mulch against the trunk (the so-called mulch volcano) traps moisture against the bark and invites rot and pests, so extension guidance is to keep mulch about 2-3 inches off trunks and stems. For an irregular bed, split it into rectangles and circles and add the areas, or use the multiple-beds shape to total up to three beds at once.

Rubber playground mulch, pine straw, and what this tool leaves out

The rubber playground mode sizes loose-fill safety surfacing, where depth is set by how far a child could fall from the equipment rather than the 2-4 in landscape band — deeper falls need deeper fill. It outputs volume only: rubber mulch's bulk weight is quoted inconsistently across suppliers, so a tons figure would be a guess, and the fall-height depths are a starting point to confirm against CPSC playground-surfacing guidance, not a tested safety guarantee. Two jobs this tool deliberately does not do: it does not size pine straw, which is sold in bales and follows a different coverage rule (use the pine-straw calculator), and it does not estimate a deeper soil fill or grading job (use the topsoil calculator). For gravel or stone sold by the ton, use the gravel calculator.

References

  1. Using Mulch in the Garden

    Iowa State University Extension and Outreach · accessed 2026-07-19

  2. Mulching Trees and Shrubs

    University of Maryland Extension · accessed 2026-07-19

  3. NIST Handbook 44 — unit definitions (yard, foot)

    National Institute of Standards and Technology (NIST) · accessed 2026-07-19

  4. Public Playground Safety Handbook (Publication 325)

    U.S. Consumer Product Safety Commission (CPSC) · accessed 2026-07-19

Frequently asked questions

How many bags of mulch are in a cubic yard?
It depends on the bag's size, not its weight. A cubic yard is 27 cubic feet, so the count is 27 ÷ the bag's cubic feet: a 2 cu ft bag (the most common retail size) is 13.5 bags per cubic yard, a 3 cu ft bag is 9, and a 1.5 cu ft bag is 18. In practice you round up — you cannot buy half a bag — so a full cubic yard of 2 cu ft mulch is 14 bags. The calculator keys its bag count to the size you pick.
How many square feet does a yard of mulch cover at 2 inches deep?
About 162 square feet. One cubic yard is 27 cubic feet, and coverage is 27 × 12 ÷ depth in inches, so at 2 inches deep a yard covers 324 ÷ 2 = 162 sq ft. Change the depth and the coverage changes with it: 324 sq ft at 1 inch, 108 sq ft at 3 inches, and 81 sq ft at 4 inches. Deeper mulch covers less ground, which is why depth is the input worth getting right.
How much will 25 bags of mulch cover?
For the common 2 cu ft bag, 25 bags is 25 × 2 = 50 cubic feet — about 1.85 cubic yards. Spread 3 inches deep that covers about 200 square feet (50 × 12 ÷ 3); at 2 inches deep it stretches to about 300 square feet. Because deeper mulch covers less ground, the depth you choose drives the answer. The tool's reverse mode returns this directly: enter the bags you have and your depth.
What depth of mulch should I use?
Two to four inches for organic mulch, according to Iowa State Extension, with finer material (shredded bark, grass clippings) toward the lower end and coarser material (wood chips) toward the higher end. A practical split: 3 inches for a new bed, about 2 inches to refresh a bed that still has some mulch, and up to 4 inches for coarse mulch or heavier weed suppression. Going much past 4 inches wastes mulch and can starve roots, so the tool flags any depth over 6 inches as unusual. The depth presets fill in 2, 3, or 4 inches in one tap and stay editable.
Is it cheaper to buy mulch in bulk or in bags?
It depends on your local prices. Bagged mulch is convenient for a bed or two, but bulk mulch (loose, sold by the cubic yard) is usually cheaper per yard once you pass roughly a cubic yard — about 13-14 bags of 2 cu ft — where bag prices and hauling add up. There is no universal cutoff, because it turns on your local bag price, bulk price, and any delivery minimum or fee, so enter both prices in the tool's optional pricing panel and it will tell you which is cheaper at your size.
How much mulch do I need around a tree?
Mulch a tree as a ring, not a solid circle, and keep it off the trunk. In the tool's ring-around-a-tree shape, enter the outer radius of the mulched circle and a trunk gap as the inner radius. For a ring 4 feet in radius with a 6-inch bare gap around the trunk, at 3 inches deep, the ring area is about 49 square feet, which needs about 0.46 cubic yards or 7 bags of 2 cu ft. Keep mulch a few inches (about 2-3 in) back from the trunk — University of Maryland Extension says it should never touch the bark — to avoid the trapped moisture, rot, and pests of a 'mulch volcano.'
How do I calculate mulch for a round or odd-shaped bed?
Break the bed into simple shapes, find each area, and add them up. The tool has a round-bed shape (enter the diameter and it uses π × radius²) and a multiple-beds shape that totals up to three rectangles at once. For a curved or L-shaped bed, split it into rectangles and circles, add the square footage, then apply your depth. A round bed 12 feet across at 3 inches deep, for example, is about 113 square feet — roughly 1.05 cubic yards or 15 bags of 2 cu ft.
What is the 3-3-3 rule for mulch?
It is a popular memory aid, not an official standard: roughly 3 inches of mulch deep, kept about 3 inches back from the trunk, spread out to about a 3-foot radius around a tree. The depth and trunk-gap parts line up well with extension guidance — Iowa State Extension recommends 2-4 inches deep and University of Maryland Extension says to keep mulch about 3 inches off the trunk — but the '3-foot' ring is just a rule of thumb; size the ring to the tree and bed, out toward the drip line where you can. Treat 3-3-3 as an easy reminder, not a specification.
How much rubber mulch do I need for a playground?
Switch to the rubber-playground mode, which sizes loose-fill by how far a child could fall from the equipment rather than by the 2-4 inch landscape band — deeper falls need deeper surfacing. A 20 × 10 ft area (200 sq ft) rated to a 12-foot fall height uses 6 inches of fill, which is 200 × 0.5 = 100 cubic feet, or about 3.70 cubic yards / 50 bags of 2 cu ft. The tool reports volume only: rubber mulch's bulk weight is quoted inconsistently across suppliers, so a tonnage figure would be a guess. Treat the fall-height depths as a starting point to confirm against CPSC playground-surfacing guidance, not a tested safety guarantee.
How much pine straw do I need?
This calculator will not size pine straw, and that is on purpose. Bark, wood-chip, and rubber mulch are bought by volume — cubic yards and bags — but pine straw is sold in bales, each covering a set area, so it follows a different formula (bales = area ÷ coverage per bale) rather than cubic-yard math. Use a dedicated pine-straw calculator that works in bales. For gravel or stone sold by the ton use the gravel calculator, and for a deeper soil fill the topsoil calculator.
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