Mulch Calculator for Beds, Tree Rings and the Spring Refresh

By the time the beds have drained and the last of the winter sand has been raked out of the borders, you can see exactly what you are dealing with: how much bare ground shows through, how flat last year's layer has gone, and where the edge has crept out into the lawn. Measure it then. This mulch calculator wants feet and inches, not guesses.

The beds tell you when they are ready

Mulch goes on once the ground has drained and warmed a little, which in most of the state means after mud season rather than at the first mild spell. Spread it over cold saturated soil and it holds the wet in.

The point of the layer is the opposite: shredded bark holds moisture through the dry stretch of July and August, and shades out the weeds that would otherwise start in May.

One thing worth knowing about a delivered pile. Spread it within a week or two. A heap left standing a month heats in the middle and sours, and sour mulch is unpleasant to handle and no good on plants.

What to measure, and when to measure it

Rake the old layer loose before you put a tape anywhere near it. Matted mulch reads deeper than it is, and you will under-order.

Then take the beds as they actually run.

Borders and foundation strips. Length along the house or the edge, width at the average, not at the widest bulge.

Tree rings. Diameter straight across. Circle mode does the rest.

Island beds and odd shapes. Break them into two or three rectangles and use multiple areas, which totals up to five separate pieces into one figure. Easier and more honest than trying to average a kidney shape.

Depth is the other half of it, and this is where mulch differs from everything else on the site. Deeper is not better.

Past 4 inches roots start running short of air. A volcano of bark heaped against a trunk rots it and houses rodents; a flat doughnut does the job.

The material choice does not change the arithmetic. Shredded bark knits together and stays put on a gentle slope. Chips and nuggets hold their shape longer but a hard downpour floats them out of a bed and along the drive. Dyed mulch keeps its color and breaks down slowly. All of them are measured the same way, by volume, so the decision is about appearance and how often you will be back, not about how much to order.

Running the numbers, and the 5% box you can untick

Shape first: rectangle, circle, or multiple areas. Length, width and diameter in feet, depth in inches anywhere from 0.25 to 24. Then the material select, which is what sets the weight.

Untick the 5% compaction and spillage box for mulch. Nobody compacts a bed. Round the yardage up instead and put the spare behind the garage.

Results are cubic yards, tons and cubic feet, and Email my quote will send them over.

Why the ton figure looks so small

Shredded mulch weighs about 600 lb per cubic yard, which is 0.30 tons. It is the lightest thing sold here by a wide margin, and that is why mulch is ordered by the yard and not by weight.

For the bag comparison, a cubic yard is 27 cubic feet, so it equals 13.5 of the 2 cubic foot bags. Multiply your yardage by 13.5 and you have the store equivalent.

Formula for checking by hand: cubic yards = area sq ft x depth in, divided by 12, divided by 27.

A foundation border down the sunny side of the house

Hypothetical. A strip 44 feet long and 4 feet deep, bare in patches, going down at 3 inches.

• 44 x 4 = 176 sq ft
• 176 x 0.25 ft = 44 cu ft
• 44 / 27 = 1.63 cu yd
• 1.63 x 13.5 = 22 bags, if you were buying it that way
• 1.63 x 0.30 = 0.49 tons

Keep the last 6 inches next to the siding clear and run the layer at 2 to 3 inches there.

Five tree rings out on the lawn

Hypothetical. Five maples, each ringed 5 feet across, at 3 inches.

• One ring: 2.5 x 2.5 x 3.14 = 19.6 sq ft
• Five rings: 98 sq ft
• 98 x 0.25 ft = 24.5 cu ft
• 24.5 / 27 = 0.91 cu yd
• 0.91 x 13.5 = about 12 bags

Under a yard for the lot, which is the sort of job where the multiple-areas option saves a second trip. Add the rings to the borders in one calculation and order once.

Shape each ring level and hold it back off the bark.

If the bed needs building rather than topping, that is a different order. Garden soil goes in first and is sized on the bed soil tool, while a thin lawn or a bare strip wants loam by the yard before any bark goes near it. Beds that are tired of being re-mulched every spring are candidates for pea stone instead of bark, which stays where it is put.

Then open shredded mulch, set a quantity and a date, and delivery is arranged at checkout by ZIP code. What the truck needs is firm ground and clear room to tip, and fresh concrete stains, so pick the drop spot before the load is booked rather than after. Every calculator on the site sits on one page if the job has more to it.

Common questions

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