Mulch Calculator (2026)
Enter your bed size and depth to find out how many bags of mulch you need, and what it will cost.
Calculate Your Mulch
The longest side of the bed, in feet. For irregular beds, use the average length.
The shorter side of the bed, in feet. For irregular beds, use the average width.
3 inches is the standard depth for garden beds. Use 2 inches for a light top-up.
Most bagged mulch is sold in 2 cubic foot bags; check the label on the bag.
The store price of one bag of mulch.
If you can buy loose bulk mulch, enter its price per cubic yard to compare. Leave it blank to skip the comparison.
Bags are always rounded up: a partial bag cannot be bought, so the calculator adds a whole bag for any remainder. The result does not include the 10% extra many gardeners order for settling and uneven ground; see the guide below if you want that buffer.
How Mulch Is Measured
Mulch is sold by volume, not by weight. Bagged mulch is labelled in cubic feet, usually 2 cubic feet per bag, while loose bulk mulch is sold by the cubic yard. One cubic yard equals 27 cubic feet. That conversion is the only bridge you need: once you know the cubic feet your bed needs, dividing by 27 gives cubic yards, and dividing by the bag size gives the number of bags.
The calculator works from your bed’s area and your chosen depth. Area is length times width. Volume in cubic feet is area times depth in feet, which is depth in inches divided by 12. Everything else follows from those two steps.
The Formula
Volume (cu ft) = area times depth in inches divided by 12
Volume (cu yd) = volume (cu ft) divided by 27
Bags needed = volume (cu ft) divided by bag size, rounded UP
Total bag cost = bags needed times price per bag
Bulk cost = volume (cu yd) times price per cubic yard
The Coverage Rule: How Far One Cubic Yard Goes
One cubic yard of mulch is 27 cubic feet. How much ground it covers depends entirely on depth: coverage equals 27 divided by the depth in feet. At 3 inches deep, one cubic yard covers 108 square feet (27 divided by 0.25 feet). Garden centres often round that to about 100 square feet, which is a handy approximation but slightly short. At 2 inches it covers 162 square feet, and at 4 inches it covers 81 square feet.
| Depth | One cubic yard covers | One 2 cu ft bag covers |
|---|---|---|
| 2 inches | 162 sq ft | 12 sq ft |
| 3 inches | 108 sq ft (often quoted as about 100) | 8 sq ft |
| 4 inches | 81 sq ft | 6 sq ft |
The bag column follows the same rule: a 2 cubic foot bag at 3 inches covers 8 square feet (2 divided by 0.25 feet). Use the table for a quick sanity check on the calculator’s answer.
Worked Example: 20 by 10 Feet at 3 Inches
| Calculation | Result | |
|---|---|---|
| Area | 20 ft times 10 ft | 200 sq ft |
| Volume | 200 times 3 divided by 12 | 50 cu ft |
| Volume in yards | 50 divided by 27 | 1.85 cu yd |
| Bags (2 cu ft) | 50 divided by 2, rounded up | 25 bags |
| Bag cost at $4 per bag | 25 times $4 | $100.00 |
| Bulk cost at $35 per cu yd | 1.85 times $35 | $64.81 |
In this example bulk mulch is $35.19 cheaper than bags, which is typical: loose mulch usually wins on price once you need more than about a cubic yard, while bags win on convenience and on small jobs where delivery fees would eat the saving.
Should You Order About 10% Extra?
Many gardeners order roughly 10% more mulch than the calculation says. Fresh mulch settles and compacts over the first few weeks, beds are rarely perfect rectangles, and a little always spills during spreading. The calculator deliberately does NOT add this buffer to its result, so the number you see is the exact volume for your stated dimensions. If your bed has curves, slopes, or uneven ground, add about 10% yourself: multiply the bag count by 1.1 and round up again. For the default example, 25 bags plus 10% is 27.5, so 28 bags.
Bags vs Bulk: Which Is Cheaper?
- Small beds (under about 1 cubic yard): bags are usually the better deal. A delivery fee on a small bulk order can cost more than the mulch itself, and bags let you buy exactly what you need.
- Large beds (over about 2 cubic yards): bulk is almost always cheaper per cubic foot, and far less packaging to dispose of. Check delivery fees and minimum orders before deciding.
- Access matters: bulk mulch is dumped in a pile, usually on a driveway. If the bed is far from the drop point, wheelbarrowing it adds real work. Bags can be carried to the bed one at a time.
- Quality varies: bulk mulch from a landscape supplier is often fresher and coarser than bagged mulch, which can sit in warehouses. Ask what wood it is made from either way.
How Deep Should Mulch Be?
- 2 inches: a light top-up over existing mulch, or around established trees where you only need to refresh the look.
- 3 inches: the standard for garden beds. Deep enough to suppress weeds and hold moisture, shallow enough for water and air to reach the soil.
- 4 inches: new beds, heavy weed pressure, or very hot, dry climates. Do not pile mulch against tree trunks or plant stems at any depth.
- Never more than 4 inches: deeper mulch can suffocate roots, trap too much moisture against stems, and encourage rot. Keep mulch a few inches clear of trunks.
What This Calculator Does Not Cover
- Irregular beds. Round, curved, or L-shaped beds need splitting into rectangles and circles and adding the areas together. The calculator assumes one rectangle.
- Delivery and tax. Bulk delivery fees, minimum orders, and sales tax are not included in either cost figure.
- Settling. Mulch compacts over weeks. The result is the volume at spreading depth, not the settled depth months later.
- Existing mulch. If old mulch is already on the bed, measure only the additional depth you want, not the full depth.
