Mulch Calculator
Mulching beds comes down to two questions: how deep, and how many bags. This calculator turns your bed area and depth into cubic yards and standard 2 cu ft bags, and tells you when a bulk delivery beats hauling bags. Mulch takes no compaction allowance — nothing gets tamped — so the depth you spread is the depth you order for, plus a little waste; the layer does thin over the season as it settles and decomposes, but that is an annual top-up job, not a reason to over-order in spring.
Total weight ≈ 543.21 lb (0.27 tons). Bulk material is heavy — check your vehicle's payload/GVWR; over ~1 ton, delivery is usually safer than hauling it yourself.
Bag or bulk?
You need only about 0.68 cubic yards (0.27 tons). Under ~2 cubic yards, bagged is usually the better call — you can carry the bags yourself and skip arranging a bulk drop, with no leftover pile to deal with.
- 10 × 2 cu ft bag
Quantities are planning estimates — confirm with your supplier.
How it works
We take the bed area you enter times your depth to get the volume (area × depth). Enter dimensions in feet, inches, yards, or metric — everything is converted to feet first. Depth is the decision that matters: university extension guidance puts mulch at 2–4 inches — toward 3–4 inches for trees and shrubs on well-drained soil, 2–3 inches on heavy or clay soil — and deeper is not better: past about 4 inches mulch holds too much moisture and starves roots of oxygen.
Unlike the stone bases on this site, mulch gets no compaction allowance — there is nothing to tamp. It does thin out over the season as it decomposes and settles, but the convention is to top beds up each year, not to over-order in spring trying to outrun decomposition. So the only adjustment here is the default 10% waste for spillage, raking, and uneven bed edges.
What you get: cubic yards, a 2 cu ft bag count, and weight. Mulch is sold by volume, so bags are counted by volume — your ordered cubic feet divided by 2, rounded up — and the weight (near 800 lb/yd³ for bulk hardwood) is there mainly for hauling: bone-dry mulch can run 500–700 lb/yd³ while a rained-on load can pass 1,000, so check the total against your vehicle's payload before loading a yard into a pickup.
Picking a type: shredded hardwood is the workhorse — it knits together and stays put, including on gentle slopes. Dyed mulch (black, brown, red) is shredded wood with colorant added for a color that holds its look through the season. Pine bark is lighter and slower to break down, with a classic coarse look around shrubs — but nuggets float in a downpour, so keep them out of swales and drainage paths. All three spread and cover the same, so pick by look and site, not by coverage.
Two calls the bag math can't make for you. First, bag versus bulk: a cubic yard is 13.5 bags (27 ÷ 2), so by about 1 to 1.5 cubic yards — roughly 14 to 20 bags — a loose bulk delivery starts beating the carry-and-empty routine; under that, bags stay simpler and let you split colors between beds. Second, skip landscape fabric under organic mulch: extension horticulturists consistently recommend against it in planted beds — it blocks the decomposing mulch from feeding the soil, and weeds simply root in the mulch layer on top of the fabric anyway. (Fabric belongs under river rock and other stone covers, where there is no decomposition benefit to lose.) If beds are your project's whole scope, you may also be sizing topsoil underneath — that one does settle, and its calculator orders for it.
Worked example
Planting bed, 12 ft × 8 ft, 3 in of shredded hardwood
Mulching a 12 ft × 8 ft planting bed 3 inches deep with shredded hardwood — the extension-recommended middle of the 2–4 inch range. Mulch never gets tamped, so there is no compaction to order for; just the default 10% for spillage and raking out the edges.
This lands right at the crossover where bags and bulk cost about the same effort: under it, carry bags; much past it, a loose yard dropped in the driveway wins. Either way the bag count is rounded up, so you finish the bed instead of coming up one bag short.
- Area
- 96 sq ft
- Volume (in place)
- 0.89 cu yd
- Order (compaction + waste)
- 0.98 cu yd
- Weight
- 0.39 tons
- 2 cu ft bag
- 14
Coverage at a glance
| Depth | 1 ton covers | 1 cu yd covers |
|---|---|---|
| 2" | 405 sq ft | 162 sq ft |
| 3" | 270 sq ft | 108 sq ft |
| 4" | 203 sq ft | 81 sq ft |
FAQ
How much mulch do I need?
Enter your bed dimensions and depth above and the calculator returns cubic yards and 2 cu ft bags instantly. As a rule of thumb, one cubic yard covers about 108 sq ft at 3 inches deep, and one 2 cu ft bag covers about 8 sq ft at 3 inches (12 sq ft at 2 inches). Measure beds as simple rectangles and let the 10% waste cover the curves.
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so it takes 13.5 of the standard 2 cu ft bags — call it 14, since you buy whole bags. Some stores also carry 3 cu ft bags (typically bark nuggets), which run 9 to the yard. The calculator counts 2 cu ft bags by volume and rounds up, so the count you see is the count to buy.
Should I buy mulch in bags or in bulk?
Up to about 1 to 1.5 cubic yards — roughly 14 to 20 bags — bags are usually the practical choice: no delivery fee, no pile on the driveway, and you can mix colors between beds. Past that, a bulk delivery is less money per yard and far less carrying; a typical yard of hardwood runs near 800 lb, which is also why hauling it yourself means checking your vehicle payload first. The calculator shows both numbers so the call is easy.
How deep should mulch be?
University extensions put it at 2–4 inches: aim for 3–4 inches around trees and shrubs on well-drained soil, and 2–3 inches on heavy or clay soils. Resist going deeper — a layer past about 4 inches holds excess moisture, starves roots of oxygen, and invites rot. And never pile mulch against trunks (the classic "mulch volcano"): keep it at least 6 inches back so bark stays dry, with the bed shaped like a donut, not a cone.
Does mulch compact like gravel? Do I need to order extra?
No — like the clean decorative stones (and unlike crusher run or a paver base), mulch gets no compaction allowance. There is nothing to tamp, so the calculator adds zero settlement, only 10% waste. Mulch does thin out over the season, but that is decomposition, not compaction: the layer breaks down into the soil (one of the reasons to use it), and the fix is an annual top-up at a lighter depth, not over-ordering in spring.
Is dyed mulch safe for garden beds?
The dye is usually the least of it — black and brown mulches are typically colored with carbon- or iron-oxide-based pigments, the same families used across garden products. The real question is the wood underneath: some budget dyed mulch is ground from recycled construction lumber, which can include old CCA-treated (arsenic-preserved) wood. If that concerns you — especially near vegetables — look for bags certified by the Mulch and Soil Council, which screens against treated wood, or buy un-dyed shredded hardwood from a known local source.