FAQ

How is the volume calculated?

Geometric volume is area times depth. In US units that is square feet times inches, divided by 12, which gives cubic feet. Cubic yards are cubic feet divided by 27. Cubic metres use the exact foot of 0.3048 metres.

Clemson Extension states the same yard formula as area in feet times depth in inches, divided by 324. One cubic yard is 27 cubic feet, and 27 times 12 is 324, so one cubic yard covers 324 square feet one inch deep.

Colorado State University’s table matches that identity: one cubic yard covers 162 square feet at 2 inches and 108 square feet at 3 inches.

Why might a chart disagree?

Iowa State University’s inch-to-feet table prints 2 inches as 0.166 feet. The exact depth is 2/12, which is 1/6 foot. Their worked example of 1.5 inches uses 0.125 feet, and that one is exact. This calculator uses the exact fraction, including for 2 inches.

Texas A&M AgriLife gives the exact yard formula, then also shows a shortcut that multiplies by 0.0031. One divided by 324 is not 0.0031. This calculator divides by 324 and does not use 0.0031. Their 10 by 10 foot example at 3 inches is exactly 25/27 cubic yards. They round that to 0.93 and then up to 1 yard for ordering. This calculator keeps the exact volume internally, shows volumes to at most two decimal places, and rounds the bag count upward from the full, unrounded volume.

RubberMulch.com’s landscape how-to divides 2 inches by 12 and uses 0.17 feet. The exact value is 0.1666… feet. A 10 by 20 foot bed at 2 inches is 100/3 cubic feet here, not 34.

How are bags counted?

Iowa State University says mulch is commonly sold in 2 or 3 cubic foot bags, and that you divide the cubic feet you need by the bag size. Texas A&M uses the same idea and rounds a partial bag up.

This page divides the exact volume to buy by the exact bag volume, then takes the smallest whole number that is not short. If the division lands on a whole number, that number is kept. If the volume is exactly zero, and the other entries are valid, the count is 0. Any volume above zero is at least 1 bag.

The count is a volume-bag count. Do not type a rubber bag’s pounds into the bag field. If the bag prints a cubic volume, choose custom volume and enter that volume with its unit.

What does the allowance do?

It is optional and it starts at 0. You may enter 0 through 25 percent. The percent is applied once to the geometric volume. Bags and the optional rubber weight both use that single adjusted volume. The percent is not applied a second time.

A blank allowance is not treated as zero. Type 0 if you want nothing extra.

What do 2 inches and 3 inches mean?

Clemson Extension describes a two-to-three-inch layer in plant beds and around trees and shrubs. The presets are those two depths. In metric mode the labels read 5.08 cm and 7.62 cm, which are exactly 2 and 3 inches. They are not relabeled as 5 cm or 8 cm.

Iowa State says many hardwood mulches are spread 2 to 4 inches. Colorado State says most mulches, including wood chips, are applied 3 to 4 inches, and that deeper mulch can keep water and air from the soil. Straw and leaves on that page are a different range. The calculator accepts a custom depth up to 12 inches so a typed number can be checked. That cap is not a recommendation to mulch 12 inches deep.

Switching US and metric converts complete lengths, areas, and custom depths while keeping the same physical measurement. Unfinished or invalid entries stay with the unit system where you typed them. Preset depths keep the same physical choice. Custom bag volume and density keep their own selected units. The old result clears until you calculate again.

Does rubber change the volume?

No. Organic and rubber use the same area and the same depth. RubberMulch.com says you typically need twice as much wood mulch as rubber mulch, and it also discusses playground depths. This tool does not apply either statement. If you want a different depth, type that depth.

The optional weight uses a density you can see and edit. The default is 40 pounds divided by 1.55 cubic feet, from the one-bag line on the RubberMulch.com calculator. That is exactly 800/31 pounds per cubic foot. The pallet line on that page prints 77 cubic feet for 50 bags, which is 1.54 cubic feet a bag, so the printed figures do not agree. The calculator does not average them.

The landscape product page says those bags weigh 40 pounds and says Playsafer and the landscape mulch are the same product. It does not, in the text used here, replace the 1.55 cubic foot bag line.

Recycled Rubber Products prints a 40 pound landscape bag as about 8 square feet, 1.33 cubic feet, and 0.049 cubic yards at 2 inches. Those three printed figures are not exactly the same volume, and another line in that table mixes units. This tool does not turn that 40 pound bag into a volume. Suppliers differ. Enter the cubic volume from your own bag if you are counting bags, and enter a density only if you want a weight.

Why is there no weight for bark and wood chips?

Organic bulk density changes with species, particle size, moisture, and compaction. A single number would pretend those products weigh the same. The page reports volume and volume bags only for organic mulch.

Which entries are rejected?

Required fields must be plain decimals, zero or greater: digits, with an optional dot and more digits. Blank is invalid. So are exponents, leading zeros, a leading or trailing dot, a plus or minus sign, spaces, commas, and letters. Very small positive values stay positive on screen. They are not shown as zero.

Limits are 0 to 20000 feet (6096 metres), 0 to 400000000 square feet (37161216 square metres), and 0 to 12 inches (30.48 centimetres). Allowance is 0 to 25 percent with at most 2 decimal places. Custom bag volume is greater than 0 and at most 10000 in the unit you pick, with at most 12 decimal places. Custom density is greater than 0 and at most 200 pounds per cubic foot, with at most 12 decimal places.

Hidden fields are not used. A custom bag or custom density that is blank is invalid only when that option is selected. Changing a used entry clears the old result immediately. Reset restores the defaults and clears errors and results.

What happens at zero?

If every required entry is valid and the volume is exactly zero, the bag count is 0. A blank size is an error, not a zero result. A tiny positive volume is at least one bag, and the volume line keeps a non-zero figure.

Does this cover playgrounds?

No. Do not use it to choose a fall-protection depth or to claim a critical fall height. It is a landscape volume calculator only.

Do you store what I type?

No. The privacy page describes that. Usage measurement excludes entered values and results. See the privacy notice for details.