Rather skip the math and the wheelbarrow? We clear and edge the beds, deal with the old compacted mulch and spread fresh mulch at the right depth, for homes in West Seneca and the towns around it.
The mulch math in plain words
Mulch is sold by volume, so you need three measurements: length, width and depth. Measure the bed in feet. Decide on the depth in inches. Multiply the three numbers together and you have a figure in a mixed unit that nobody sells.
Dividing by 324 turns that figure into cubic yards, the unit bulk mulch is sold in. The 324 comes from 12 inches in a foot times 27 cubic feet in a cubic yard. If you buy bags instead, divide by 12 to get cubic feet, then divide by the size printed on the bag. Always round up. A bed that comes out a little short looks patchy, and the leftover from a small overage is easy to tuck into another bed.
A worked example for one front bed
Say your front foundation bed runs 30 feet along the house and is 6 feet deep from the wall to the lawn edge. You want 3 inches of mulch.
Start with 30 times 6, which is 180 square feet of bed. Multiply by 3 inches to get 540. Divide 540 by 324 and you get about 1.7 cubic yards. Round that up and order 2 yards.
If you would rather buy bags, take the same 540 and divide by 12. That gives 45 cubic feet. With 2 cubic foot bags you would need 23 bags, rounded up. That is a lot of bags to carry, which is why most homeowners with more than one bed switch to bulk mulch or have it installed.
How deep should mulch be?
For flower beds and shrub beds, 2 to 3 inches of finished depth is the target. Less than 2 inches lets weeds push through and dries out fast in a July heat spell. More than 3 inches starts to hold too much water against the roots, and that matters here because so many Southtowns yards sit on heavy clay that already drains slowly.
Keep mulch pulled back a few inches from shrub stems and tree trunks. The mounded volcano look around trees traps moisture against the bark and invites rot and rodents.
Before you order, push a trowel into the bed and check what is already there. If last year's layer is still 2 inches deep, you only need a thin top dressing, not a full 3 inches on top of it.
Using the mulch calculator on this page
The calculator does the same math for you. Enter the length of the bed in feet, the width in feet and the depth you want in inches. It returns the cubic yards and the number of bags for the bag size you choose.
Run each bed separately and add the totals. A long front bed, a mailbox bed and a ring around a tree are three different shapes, and lumping them together usually throws the number off.
If you are only topping up, enter the depth you are adding, not the total depth you want to end with. When you are unsure, measure the existing layer first and subtract it from your target.
Measuring curved and odd-shaped beds
Very few beds are perfect rectangles. For a curved bed, measure the length along the house and take the width at three or four points, then use the average width. That gets you close enough to order.
For a round bed around a tree, measure across the circle, halve it to get the radius, multiply the radius by itself and then by 3.14. That gives square feet. Multiply by the depth and divide by 324 just like before.
Triangle corner beds are half of a rectangle. Measure the two straight sides, multiply them, and cut the result in half. Then carry on with the depth and the 324.
Bags or bulk, and when to put it down
Bags make sense for one small bed or a quick touch-up. Once a project passes a yard or two, bulk is easier to handle and less plastic to throw away, but it needs a spot on the driveway and a wheelbarrow.
Timing matters as much as quantity in Western New York. In spring, wait until the soil has thawed and started to dry so you are not sealing cold, soggy ground under a blanket. A fall layer, laid after the cleanup, insulates roots through the freeze and thaw swings of a lake-effect winter.
If you would rather skip the measuring and the wheelbarrow, our mulching crew clears and edges the beds first, deals with old compacted mulch and spreads the new layer at the right depth.
The short version
- Length in feet times width in feet times depth in inches, divided by 324, equals cubic yards.
- A 30 by 6 foot bed at 3 inches needs about 1.7 cubic yards, so order 2.
- Aim for 2 to 3 inches of finished depth and keep mulch off stems and trunks.
- Check the depth of last year's layer before you order more.
- Measure each bed on its own and round every answer up.
Quick answers
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet. With 2 cubic foot bags that works out to 13 and a half bags, so plan on 14. With 3 cubic foot bags it is 9.
How many square feet does one yard of mulch cover?
At 3 inches deep, one cubic yard covers about 108 square feet. At 2 inches it stretches to about 162 square feet.
Should I remove old mulch before adding new mulch?
Not always. If the old layer is thin and loose, rake it to break it up and add a top dressing. If it has packed into a hard mat or is piled too deep, it should come out first. See our guide to the best mulch for flower beds for which types last longest.
Is 4 inches of mulch too much?
For most beds, yes. Past 3 inches the layer holds too much water against roots, especially on clay, and it can keep light rain from reaching the soil.
What does mulch installation depend on if I hire it out?
Total bed area, the depth, the type of mulch and how much edging and weeding the beds need first. Our landscaping cost guide covers what moves the number, and the estimate is free.
Want this done for you? Patrick comes out, looks at the yard and talks through the options. The estimate is free.