gizmobench

Mulch Calculator

Type the bed and the depth you are spreading and read the mulch in cubic yards, cubic feet, cubic metres and bags at once, with the arithmetic printed under the answer. The bag size is a field on this page rather than a number we picked for you: it opens at 2 cubic feet, which is the commonest bag, and whatever your own bag says types straight over it. A 20 by 8 foot bed at 3 inches is 40 cubic feet, 1.48 cubic yards and 20 bags of 2 cubic feet, and the page shows you the 160 square feet and the division that got there. Beds can be rectangles or circles measured across, in feet or in metres, and the depth is in inches either way, with 2, 3 and 4 inches one click each. There is no price field anywhere here, because a rate per bag is a price list and a price list goes stale.

20 ft8 ft3 in deep
What you need3 in over 160.00 sq ft
Cubic yards
1.48
40.00 cu ft · 1.13 m³
20 bags at 2 cu ft, rounded up
160.00 sq ft x 3 in / 12 = 40.00 cu ft / 27 = 1.48 cu yd
40.00 / 2 = 20.00, rounded up
Length
Width
Depth in inches
Bag size cu ft
Bed measured in

The bag size is a field because it is the one number a calculator cannot know: it opens at 2 cubic feet, which is the commonest bag, and the figure on your own bag types straight over it. Depth is in inches whichever unit the bed is measured in, since that is how mulch depth is quoted: 2 inches is a top-up over mulch that is already down, 3 inches is the usual laying depth for a bed, and 4 inches is over bare soil, where the mulch does the whole job. In centimetres those are 5.1, 7.6, 10.2. Switching the bed between feet and metres rewrites what you already typed into the other unit, to four decimals, rather than clearing it.

  • A 20 by 8 bed3 in, the usual laying depth
    1.48 cu yd, 20 bags of 2 cu ft
  • The same bed at 4 ina first laying over bare soil
    1.98 cu yd, 27 bags of 2 cu ft
  • A 12 ft circlemeasured across, 3 in deep
    1.05 cu yd, 15 bags of 2 cu ft
Exact on the arithmetic, honest about the rest. Exact arithmetic on the dimensions you enter: area times depth, converted without rounding until the last step. It cannot know how far mulch settles once spread, what a brand actually puts in a bag, or that your bed is the rectangle you described. The working is printed under the answer so every step can be checked: the area, the area times the depth, and the division the bag count rounds up from. There is no field for money on this page and no supplier, because a rate is a list that goes stale and a quantity does not.

Common questions

How much mulch do I need for a 20 by 8 foot bed?
At 3 inches deep, the depth most beds are laid at, a 20 by 8 foot bed takes 40 cubic feet of mulch. That is 1.48 cubic yards, 1.13 cubic metres, or 20 bags if your bags hold 2 cubic feet each. Change the depth and the answer moves with it: the same bed at 2 inches, which is a top-up over mulch that is already down, takes 26.67 cubic feet, 0.99 cubic yards and 14 bags, and at 4 inches over bare soil it takes 53.33 cubic feet, 1.98 cubic yards and 27 bags. The working is printed under the figure so you can follow it: 160 square feet of ground, times 3 inches divided by 12 to put the depth in feet, is 40 cubic feet, and 40 divided by 27 is 1.48 cubic yards.
How deep should mulch be laid?
The three depths the page offers as one click each are the ones people commonly lay. Two inches tops up a bed that already has mulch on it and has just thinned over a season. Three inches is the usual laying depth for a bed, deep enough to hold moisture and keep light off weed seed. Four inches is what it takes over bare soil, where the mulch is doing the whole job of covering the ground. Deeper than that starts to keep water off the roots rather than in the soil, and mulch piled against a trunk holds damp where the bark wants air. The page does not pick the depth for you: it takes the one you have decided on, and the field accepts any number, so 2.5 or 1.5 inches works the same way.
How many 2 cubic foot bags are in a cubic yard of mulch?
A cubic yard is 27 cubic feet, so 2 cubic foot bags come to 13.5 of them, and since half a bag is not something a shop sells the page rounds that up to 14. Bags of 3 cubic feet make exactly 9 to the yard, bags of 1.5 make 18, and 1 cubic foot bags make 27. The other direction is worth knowing when you are standing in the aisle: one cubic yard spread 3 inches deep covers 108 square feet, at 2 inches it covers 162, and at 4 inches it covers 81.
Does the calculator know what size bags my supplier sells?
No, and nothing on this page assumes one. The bag size is a field you fill in, because it is the one figure a calculator cannot know: bagged mulch is sold at 1, 1.5, 2 and 3 cubic feet depending on the brand and the country, and a bag count worked from someone else's bag is a bag count you cannot check against the bag in your hand. The field opens at 2 cubic feet, which is the commonest size on a pallet, and the number printed on your own bag types over it. Every bag count on the page, including the three worked examples underneath, is recomputed from whatever is in that field.
Can I measure the bed in metres instead of feet?
Yes. The Bed measured in switch takes the length, width or diameter in metres, and the answer still comes out in cubic yards, cubic feet and cubic metres together, so you can order in whichever unit your supplier quotes. Switching the unit rewrites the measurements you have already typed into the other one rather than clearing them, to four decimals, which is exact both ways because a foot is 0.3048 metres. A 6 by 2.4 metre bed at 3 inches is 1.10 cubic metres, 38.75 cubic feet and 1.44 cubic yards, or 20 bags of 2 cubic feet. The depth stays in inches whichever unit the bed is in, because that is how mulch depth is quoted and sold; 2, 3 and 4 inches are 5.1, 7.6 and 10.2 centimetres.
How do I work out a round bed or a tree ring?
Pick the Circle shape and measure straight across the widest point, through the middle, not from the middle out. The page takes that diameter, halves it and works the area as pi times the radius squared. A 12 foot circle at 3 inches is 113.10 square feet, 28.27 cubic feet, 1.05 cubic yards and 15 bags of 2 cubic feet. For a ring around a tree with a gap in the middle, work out the whole circle, then the bare circle in the middle, and take the second away from the first.
Is anything uploaded, and does it cost anything?
No. The arithmetic runs in your browser, there is no account and nothing is sent anywhere. Your measurements, the shape, the unit, the depth and the bag size are kept in your browser's own storage so the page opens where you left it, and clearing your browser data clears that too. There is no price field, no supplier and no delivery charge on this page: a rate per bag or per yard is a local number that moves, and a quantity does not, so the page gives you the quantity and leaves the money to whoever is quoting you.

Exact arithmetic on the dimensions you enter: area times depth, converted without rounding until the last step. It cannot know how far mulch settles once spread, what a brand actually puts in a bag, or that your bed is the rectangle you described.