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Mulch Calculator

Measure the bed, choose how deep you're mulching, and get the bag count, plus the cubic-yard figure, so you can see instantly whether bags or a bulk delivery is the smarter buy.

Diagram of a bed of material such as mulch or gravel, showing the area and the depth of the layer
A bed of material is just a shallow box: area × depth, then bags or bulk yards.

Your buy-list

Enter your measurements

How the mulch quantity is calculated

Volume is area × depth (depth converted from inches to feet). One cubic yard is 27 cu ft, and the standard bag of mulch holds 2 cu ft, so 13.5 bags make a cubic yard. Bags also come in 1.5 and 3 cu ft sizes; pick the size on your bag and the count follows.

Depth is the decision that drives everything: 3 in is the standard working depth for weed suppression and moisture retention, 2 in is enough for a colour refresh over existing mulch, and 4 in suits new beds and tree rings. Under 2 in, weeds push through; much over 4 in can starve roots of air and water.

Rule of thumb for the bags-vs-bulk decision: once a job passes roughly 3 cubic yards (40+ bags), a bulk delivery usually wins on price and effort. The result panel shows both numbers every time. Filling the beds with soil first? The Topsoil Calculator works in the same bags and cubic yards.

Worked examples

20 × 4 ft flower bed, 3 in deep

20 cu ft of mulch in standard 2 cu ft bags.

Buy 10 bags

500 sq ft of beds, 2 in refresh

83.3 cu ft in 2 cu ft bags, or 3.09 cu yd in bulk.

Buy 42 bags

12 × 12 ft bed, 4 in deep

48 cu ft, 10% extra for settling, 1.5 cu ft bags.

Buy 36 bags

Frequently asked questions

How many bags of mulch do I need for 100 sq ft?
At 3 in deep, 100 sq ft needs 25 cu ft: 13 standard 2 cu ft bags. At 2 in deep it's about 9 bags; at 4 in, 17 bags. Depth changes the answer more than anything else.
How many bags of mulch are in a cubic yard?
13.5 bags at the standard 2 cu ft size (a cubic yard is 27 cu ft). With 3 cu ft bags it's 9 bags per yard; with 1.5 cu ft bags, 18.
How deep should I spread mulch?
3 in for most beds, enough to suppress weeds and hold moisture. Use 2 in to refresh existing mulch and up to 4 in for new beds and tree rings, keeping mulch a few inches away from trunks and stems.
Bags or bulk: which is cheaper?
Bulk, once the job is big enough to justify a delivery: one cubic yard is 13.5 bags' worth of mulch with no plastic to open, and past a few yards, delivered bulk normally works out far cheaper per yard than retail bags. For one or two small beds, bags win on convenience and no leftover pile.
How much area does one bag of mulch cover?
A 2 cu ft bag covers 12 sq ft at 2 in deep, 8 sq ft at 3 in, or 6 sq ft at 4 in. The coverage printed on the bag is usually quoted at 3 in.

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Estimate disclaimer: results are planning estimates based on standard manufacturer yields and coverage figures. Site conditions, product choice and installation method change actual quantities. Verify before you buy, and follow local building code for structural work. This tool does not replace professional engineering advice.

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