Mulch & Topsoil Calculator
How many cubic yards of mulch, compost or topsoil to order, what it weighs, and what to say when you ring the yard. A yard of bark covers far more ground than people expect.
Material order
What is it for?
This sets a sensible depth.
Measure the area
Add a shape for each part of the job. They are added together.
UnitsThree inches is the working depth for weed suppression in a planting bed. Deeper than four starts to smother roots and hold damp against stems.
Price it, optional
Yards sell by the yard, by the ton or by the bag. Pick whichever way yours quotes.
What to say at the yard
Read this out or paste it into an email. It gives them everything they need in one go.
Assumptions used
So you can check them against what your supplier tells you.
Why this may change
Bulk weights vary by supplier and rise sharply when the pile is wet, so order by the cubic yard where you can. Most yards have a minimum delivery and charge the same whether you take two yards or four. Mulch settles and breaks down, so a bed at a full three inches in spring will be noticeably thinner by the following one, which is why topping up is an annual job rather than a one off.
Common questions
How many cubic yards of mulch do I need?
Multiply the bed area in square feet by the depth in feet, then divide by 27. A 200 sq ft bed at 3 in deep is 50 cubic feet, or about 1.9 cubic yards. One cubic yard covers roughly 100 square feet at 3 in, or 160 square feet at 2 in, which is the quickest sense check to carry in your head.
How deep should mulch be?
Three inches in a planting bed. That is deep enough to block light from weed seeds and hold moisture, without smothering what you want to keep. Two inches is enough as a top up over an existing layer. Past four inches you start causing problems rather than solving them, particularly against trunks and stems, where piled mulch holds damp and invites rot and rodents. Pull it back a few inches from anything woody.
How much does a yard of mulch weigh?
About 800 lb for bark or wood chips, so roughly four tenths of a ton. Compost is heavier at around 1,000 lb and topsoil far heavier again at about 2,000 lb, a full ton per yard. That difference matters when you are shifting it: a yard of bark is a manageable afternoon with a wheelbarrow, and a yard of topsoil is not. Wet material weighs considerably more than the figures above.
Should I put landscape fabric under mulch?
Often not. In a planting bed, mulch breaks down into the soil, which is half the point of it, and fabric interrupts that while eventually surfacing in shreds. Fabric earns its place under gravel and stone, which do not break down, and in permanent paths. If your problem is perennial weeds, clearing them properly and mulching at a full three inches does more than fabric will.
Fill the bed, then plant it
Once you know the soil and mulch volumes, work out what will actually grow in your region and conditions.