Mulch Calculator
Calculate how much mulch you need for your garden beds — in cubic yards and number of bags — at the right depth, and compare the cost of bagged vs bulk mulch.
How much mulch do you need? Add your beds, set the depth, and get the cubic yards and number of bags to buy — plus an optional bagged-vs-bulk cost comparison. It adds up multiple beds for you.
Garden beds
Enter each bed's length and width in feet. Add a row for every separate bed.
Mulch depth
How deep to spread the mulch, in inches. 2–3 inches is ideal for most beds; going much deeper can harm plants.
Bag size
The volume of the bags you'd buy. Bagged mulch is most commonly 2 cubic feet.
Price per bag
Price per cubic yard
Optional: add prices to compare buying bags vs. bulk.
Mulch Needed
1.9 cu yd
≈ 25 bags · 200 sq ft at 3 in deep
Past a couple of yards, price out bulk
You need about 1.9 cubic yards — that's 25 bags to buy, haul, and open. Once you're past roughly 2–3 yards, bulk delivery is usually cheaper per yard and far less lifting, so it's worth getting a bulk price to compare (add prices above to do it here).
Estimates assume mulch spread evenly at the depth you set; bagged mulch is most often 2 cubic feet per bag, and a cubic yard equals 27 cubic feet (about 13–14 of those bags). Order a little extra, since mulch settles and beds are rarely perfect rectangles. Bulk mulch is usually sold by the cubic yard, often with a minimum order and a delivery fee — factor those in when comparing to bags. Keep mulch 2–3 inches deep and pulled back from plant stems and tree trunks, and plan to top it up about an inch a year as it breaks down.
💡About this calculator▼
Mulch is one of the cheapest, highest-impact things you can do for a garden — but guess wrong on the amount and you either run out mid-project or end up with a pile of leftover bags. This calculator tells you exactly how much you need, in both cubic yards and number of bags, so one trip does it.
Add each garden bed's length and width, set how deep you want the mulch, and the tool sums the beds, works out the volume, and converts it to cubic yards and bags. Add optional prices and it'll also compare buying bags against ordering bulk, so you can see which is cheaper for your size of job.
It also keeps you honest on depth. Two to three inches is the sweet spot for most beds — enough to suppress weeds and hold moisture — while piling it deeper actually harms plants. The calculator flags it if you go too deep, so you buy the right amount and your plants stay healthy.
Mulch is sold by volume, so the calculation is volume-based and simple.
First the tool adds up the area of your beds — length times width for each, summed across all of them. Then it multiplies that total area by the depth (converted from inches to feet) to get the volume in cubic feet.
From there it converts to the two units you actually buy in. Cubic yards is the bulk unit: one cubic yard is 27 cubic feet, so it divides the volume by 27. Bags is the retail unit: it divides the volume by your bag size (most bagged mulch is 2 cubic feet) and rounds up to whole bags, since you can't buy a partial one.
If you enter prices, it estimates both ways: the bagged cost is the number of bags times the price per bag, and the bulk cost is the cubic yards times the price per yard. Comparing them shows where the crossover falls — bags are convenient for small jobs, but bulk gets cheaper per yard (and saves a lot of lifting) once the job is more than a couple of yards. The exact formula and a worked example are below.
📐How it's calculated▼
It's an area-times-depth volume, converted to yards and bags.
Step 1 — Total area: Total area = sum of (length × width) for every bed
Step 2 — Volume: Volume (cu ft) = Total area × (Depth in inches ÷ 12)
Step 3 — Convert: Cubic yards = Volume ÷ 27 Bags = Volume ÷ bag size (e.g. 2 cu ft), rounded up
Optional cost: Bagged cost = Bags × price per bag Bulk cost = Cubic yards × price per cubic yard
Example: One 20 × 10 ft bed at 3 inches deep, 2-cu-ft bags
→ Area: 20 × 10 = 200 sq ft
→ Volume: 200 × (3 ÷ 12) = 50 cu ft
→ Cubic yards: 50 ÷ 27 ≈ 1.9 cu yd
→ Bags: 50 ÷ 2 = 25 bags
So that bed needs about 1.9 cubic yards, or 25 bags. At $4 a bag that's $100 in bags; if bulk runs $40 a yard, it's about $74 — bulk already edges ahead at this size.
📎Source: University of Illinois Extension — Mulching Guidance
🔍Finding your inputs▼
Garden beds: Enter the length and width of each bed in feet, adding a row for every separate bed — the calculator sums them so you get one combined total. For an irregular or curved bed, approximate it as a rectangle (length × average width) or break it into a couple of rectangles; mulch is forgiving, and rounding up slightly is fine. For a ring around a tree, you can estimate it as a square roughly the diameter of the ring.
Mulch depth: How thick to lay the mulch, in inches. Two to three inches is the standard recommendation for most beds — deep enough to block weeds and retain moisture, not so deep that it harms plants. Use 2 inches for a light refresh over existing mulch, 3 inches for a fresh full layer. Going beyond about 4 inches is counterproductive (and the calculator will warn you).
Bag size: The volume of the bags you'll buy, since this sets the bag count. Bagged mulch is most commonly sold in 2-cubic-foot bags; some brands and types use 1.5 or 3. Check the bag if you can — it changes how many you need.
Price per bag / price per cubic yard: Both optional. Enter the per-bag price to estimate the bagged total, and the bulk per-yard price to compare. If you only have one, the calculator still shows that cost; enter both to see which is cheaper for your job. Leave them blank to just get the quantity.
⚠️Special situations▼
My beds are curved or irregular, not rectangles
Approximate. For a curved or kidney-shaped bed, estimate a length and an average width and enter it as a rectangle — mulch quantity doesn't need to be exact, and rounding up a little is the safe direction. For a complex shape, split it into two or three rough rectangles and add them as separate beds. For a circular ring around a tree, a square about as wide as the ring's diameter is a fine stand-in. The goal is a good estimate, not survey-grade precision.
Should I buy bags or order bulk?
It comes down to size and effort. For under about a cubic yard (roughly 13 bags), bags are the easy choice — no delivery fee, and you buy exactly what you need. From one to three yards it's a toss-up: weigh the bag price against the bulk price plus delivery, and how much lifting and bag-opening you want to do. Past three yards or so, bulk almost always wins on both cost per yard and labor, despite delivery fees. Enter both prices above to see the actual crossover for your job.
How deep should mulch be?
Two to three inches is ideal for most beds — enough to suppress weeds, hold moisture, and moderate soil temperature. Go with 2 inches when topping up over existing mulch (you're just replenishing what broke down), and 3 inches for a fresh layer on bare soil. Avoid exceeding 3–4 inches: too-deep mulch can keep water from reaching roots, suffocate them, and harbor pests and disease. The exception is never pile it against stems or trunks at any depth — always leave a few inches of clearance.
How often do I need to re-mulch?
Most organic mulches (shredded bark, wood chips) break down over a year or two, so plan to refresh annually — but usually just a top-up of about an inch to bring it back to 2–3 inches, not a whole new layer. Rake and fluff the existing mulch first; if it's matted, loosening it can be enough on its own. To estimate a top-up here, just set the depth to the inch or so you're adding rather than the full 3 inches, and the calculator gives you the smaller refill amount.
Does the type of mulch change how much I need?
Not the quantity — volume is volume, so a cubic yard of shredded hardwood and a cubic yard of pine bark cover the same area at the same depth. What changes is how it's sold, how it settles, and how long it lasts: finer or shredded mulches knit together and may settle a bit more, while chunky bark nuggets stay loose. Rubber and stone 'mulch' are sold by volume too but weigh far more (stone is sold by the ton, not the yard), so this calculator is aimed at organic mulches; for stone, use a gravel/aggregate calculator instead.
❓Common questions▼
How much mulch do I need?
Multiply your bed area by the depth to get volume, then convert. For a single 20 × 10 ft bed at 3 inches deep, that's 200 sq ft × 0.25 ft = 50 cubic feet, which is about 1.9 cubic yards or 25 standard 2-cubic-foot bags. The calculator above adds up multiple beds and does the conversion for you, and can compare bag vs bulk cost. A good rule: 2–3 inches deep, and order a little extra since beds are never perfect rectangles.
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so with the common 2-cubic-foot bags it takes about 13–14 bags to equal one cubic yard (27 ÷ 2 = 13.5). With 3-cubic-foot bags it's 9, and with 1.5-cubic-foot bags it's 18. That's worth knowing for the bag-vs-bulk decision: hauling and opening 14 bags per yard is real work, which is why bulk delivery becomes attractive once you need a few yards.
How deep should I lay mulch?
Two to three inches is the standard for most garden beds — deep enough to suppress weeds and retain moisture without harming plants. Use about 2 inches when refreshing over existing mulch and 3 inches for a new layer on bare soil. Don't exceed 3–4 inches: too-deep mulch blocks water and air from reaching roots and can cause rot. And never mound mulch against plant stems or tree trunks, regardless of depth — keep a few inches of clearance.
Is it cheaper to buy mulch in bags or in bulk?
For small jobs, bags are cheaper and simpler once you factor in bulk delivery fees and minimums. For larger jobs, bulk is almost always cheaper per yard — sometimes less than half the per-volume cost of bags — and far less work than hauling and opening a dozen-plus bags per yard. The crossover is usually around two to three cubic yards. Enter your bag and bulk prices in the calculator to find the exact break-even for your project.
How much area does a cubic yard of mulch cover?
It depends on depth. A cubic yard (27 cubic feet) covers about 162 square feet at 2 inches deep, roughly 108 square feet at 3 inches, and about 81 square feet at 4 inches — the deeper you spread it, the less area it covers. At the recommended 2–3 inches, plan on one cubic yard per roughly 100–160 square feet of bed. The calculator works this out precisely for your exact beds and depth.