How much mulch do i need

The amount of mulch a bed needs comes down to two numbers you control directly: the area of the bed in square feet, and how deep you spread the mulch. Multiply the two, convert to cubic yards or cubic feet, and you have your answer. The part that trips people up is not the math, it is measuring the bed accurately and picking a depth that matches the job, since both mistakes compound into an order that is meaningfully off.

The coverage math in plain terms

One cubic yard of mulch is 27 cubic feet. Spread over a bed, that same 27 cubic feet covers more or less area depending on depth: at 1 inch deep it covers about 324 square feet, at 2 inches about 162 square feet, at 3 inches about 108 square feet, and at 4 inches about 81 square feet. So a 300 square foot bed at 3 inches deep needs roughly 300 divided by 108, which is about 2.8 cubic yards. The relationship is simple, but it means doubling the depth cuts the coverage per cubic yard in half, which is why guessing a depth without checking a reference often leads to ordering the wrong amount by a wide margin.

Typical depths by project

Most flower beds and shrub borders use 2 to 3 inches of mulch: enough to suppress weeds and hold moisture without piling material against stems. Beds under trees often use 3 to 4 inches, kept a few inches clear of the trunk itself. A path meant mainly to define a walking area rather than bear heavy traffic might use only 2 inches, since mulch paths are usually topped up more often than beds. Going deeper than about 4 inches rarely adds benefit for organic mulch and can actually suffocate roots and hold too much moisture against the soil surface.

Measuring an odd shaped bed

Rectangular beds are the easy case: length times width gives the area directly. For a circular bed, use the diameter to find the radius, then area equals pi times radius squared. For an L-shaped bed, split it into two rectangles and add the two areas together. For a bed with a curved edge, breaking it into several straight sided pieces and adding them up gets close enough for ordering purposes; landscaping estimates do not need survey level precision, just an honest accounting of every piece of the bed. The calculator on this site does exactly this: enter each part of your bed as its own rectangle or circle, and it adds the areas together automatically before applying your chosen depth.

Bags versus bulk once you have your total

Once you have a cubic yard figure, converting to bags is straightforward: a 2 cubic foot bag covers 2 cubic feet, so it takes about 13 to 14 bags per cubic yard, and a 3 cubic foot bag takes about 9 bags per cubic yard. For anything above roughly 2 to 3 cubic yards, bulk delivery is usually the cheaper route once you account for how many individual bags that would otherwise be, though delivery minimums and fees vary by supplier and are worth checking before deciding.

Use the calculator for your exact numbers

Rather than working through the arithmetic by hand for a specific bed, the gravel and mulch calculator on the homepage takes your measurements and chosen depth and returns cubic yards, cubic feet, bag counts for both common bag sizes, and wheelbarrow loads for whichever of the nine materials you are working with, including wood mulch and cedar mulch specifically.

Mulch Coverage Quick Reference

Use this table to estimate how far one cubic yard of mulch will cover at common depths.

Reference	Amount	Coverage
Bulk mulch	1 cubic yard	27 cubic feet
Light topdress	1 inch deep	324 sq ft
Thin bed layer	2 inches deep	162 sq ft
Common bed depth	3 inches deep	108 sq ft
Deep bed layer	4 inches deep	81 sq ft

Divide your bed area by the coverage number for your chosen depth to estimate cubic yards.