Mulch Calculator: Bags, Cubic Yards and Gravel Tons

Estimate only. Check product labels and local building rules before you buy or build.

Quick answer

Multiply the area in square feet by the depth in inches and divide by 12 to get cubic feet, then divide by 27 for cubic yards. A 12 × 10 ft bed covered 3 in deep needs 120 × 3 ÷ 12 = 30 cu ft of mulch, which is 1.11 cu yd or 15 bags of 2 cu ft.

How to use the mulch calculator

Choose the material: mulch, topsoil, compost, gravel or sand.
Pick the shape: length and width for a rectangular bed, the diameter for a ring around a tree, or a known area if you have already added up several beds.
Enter the depth of the finished layer in inches. The cubic yards, cubic feet, bags and area update as you type.
Open "Bag size and other assumptions" to choose the bag size on the shelf, add a margin for settling or waste, or change the bulk density (weight per cubic foot) used for gravel and sand.

How do you calculate how much mulch you need?

Mulch, soil and gravel are measured by volume: the area of the bed times the depth of the layer. The area is in square feet and the depth in inches, so divide by 12 to get cubic feet. Bulk material is sold by the cubic yard, which is 3 × 3 × 3 = 27 cubic feet.

Bags are labeled in cubic feet, so divide the cubic feet by the bag size and round up to whole bags. Gravel and sand are also sold by weight, in 50 lb bags or by the ton, so their volume is multiplied by a weight per cubic foot. The calculator starts at 100 lb per cubic foot, because the maker of play sand says a 50 lb bag holds about half a cubic foot. No manufacturer figure was found for gravel, so it starts at the same value, and bulk gravel can weigh more or less.

area (sq ft) = length × width, or 3.1416 × (diameter ÷ 2)² for a circlevolume (cu ft) = area × depth (in) ÷ 12volume (cu yd) = volume (cu ft) ÷ 27bags = volume (cu ft) ÷ bag size (cu ft), rounded upweight (lb) = volume (cu ft) × weight per cu ftweight (tons) = weight (lb) ÷ 2,000

How much area does a cubic yard of mulch cover?

One cubic yard covers 324 sq ft at 1 in deep, so divide 324 by the depth in inches. The bag columns give the bags needed for every 100 sq ft of bed, rounded up to whole bags.

Area one cubic yard covers, and bags needed for every 100 sq ft, by depth
Depth	1 cu yd covers	2 cu ft bags	3 cu ft bags
1 in	324 sq ft	5	3
2 in	162 sq ft	9	6
3 in	108 sq ft	13	9
4 in	81 sq ft	17	12
6 in	54 sq ft	25	17

For every 100 sq ft, the cubic yards needed are 0.31 at 1 in, 0.62 at 2 in, 0.93 at 3 in, 1.23 at 4 in and 1.85 at 6 in.

Worked examples

Mulch for a 12 × 10 ft flower bed

The bed covers 12 × 10 = 120 sq ft. At 3 in deep, the mulch fills 120 × 3 ÷ 12 = 30 cu ft, which is 30 ÷ 27 = 1.11 cu yd.

In 2 cu ft bags that is 30 ÷ 2 = 15 bags. In 3 cu ft bags it is 30 ÷ 3 = 10 bags. If you order bulk mulch instead, ask for 1.11 cu yd, or round to the nearest amount the yard sells.

Gravel for a 30 ft garden path

A path 30 ft long and 3 ft wide covers 90 sq ft. At 2 in deep it needs 90 × 2 ÷ 12 = 15 cu ft of gravel, which is 0.56 cu yd.

At the starting value of 100 lb per cu ft, 15 cu ft of gravel weighs 1,500 lb, or 0.75 tons. That is 1,500 ÷ 50 = 30 bags of 50 lb. The weight depends on the stone and its moisture, so for a bulk load ask the yard what a cubic yard of that stone weighs and enter it under the assumptions.

How deep should mulch be?

Spread wood and bark mulch 2 to 3 in deep, measured after it has settled. Illinois Extension gives 2 to 3 in for beds and for mulch rings around established trees, and Clemson Extension says fine wood and bark mulch should not be more than 2 to 3 in deep, while coarse pine bark nuggets can go up to 4 in.

Do not pile mulch against tree trunks. Clemson Extension says to keep mulch 2 to 3 in away from the stems of woody plants. For weed control in a bed, it says a 1 in layer of small rocks will provide good weed control.

How much does a cubic yard of gravel weigh?

At the calculator’s starting value of 100 lb per cu ft, a cubic yard of sand or gravel weighs 2,700 lb, or 1.35 tons. The figure comes from the maker of play sand, which puts a 50 lb bag at about 0.5 cu ft. A cubic yard is 27 cu ft, so it takes 54 bags of 50 lb.

Gravel has no manufacturer figure of its own here, so 100 lb per cu ft is only a starting value. Bulk gravel is weighed at the yard, and the weight per cubic yard depends on the stone and how wet it is. Ask for the figure the yard uses and type it into the bulk density box in pounds per cubic foot (divide pounds per cubic yard by 27).

Questions

How many bags of mulch make a cubic yard?

A cubic yard of mulch is 13.5 bags of 2 cu ft, so buy 14 bags, or exactly 9 bags of 3 cu ft. A cubic yard is 27 cubic feet, and bagged mulch is labeled in cubic feet, so divide 27 by the bag size. With 1.5 cu ft bags it takes 18 bags to make a cubic yard.

How much area does a yard of mulch cover?

One cubic yard of mulch covers 108 sq ft at 3 in deep, 162 sq ft at 2 in and 324 sq ft at 1 in. Divide 324 by the depth in inches for any other depth. A single 2 cu ft bag covers 8 sq ft at 3 in or 12 sq ft at 2 in, and a 3 cu ft bag covers 12 sq ft at 3 in.

How much mulch do I need around a tree?

A mulch ring 6 ft across and 3 in deep takes 7.07 cu ft of mulch, which is 4 bags of 2 cu ft. The ring covers 3.1416 × 3 × 3 = 28.27 sq ft, and 28.27 × 3 ÷ 12 = 7.07 cu ft. Choose Circle in the calculator and enter the diameter. Keep the mulch a few inches away from the trunk instead of piling it against the bark.

How many 50 lb bags of gravel are in a ton?

There are 40 bags of 50 lb in a US ton of 2,000 lb. At 100 lb per cubic foot, the figure the maker of play sand gives for a 50 lb bag, a ton fills about 20 cu ft, or 0.74 cu yd. Spread 2 in deep, that covers 120 sq ft. Gravel is a starting value: ask the yard what its stone weighs.

How many bags of sand do I need for a sandbox?

A 4 × 4 ft sandbox filled 6 in deep needs 8 cu ft of sand, which is 16 bags of 50 lb. Each 50 lb bag of play sand holds about 0.5 cu ft, so double the cubic feet to get the number of bags. The manufacturer’s own chart gives the same 16 bags for that box and notes that its figures do not allow for waste or an uneven base.

Sources

University of Illinois Extension, Mulch Madness (Over the Garden Fence, 2017) (checked October 19, 2026)Mulch 2 to 3 in deep once settled in beds and tree rings; do not pile it against trunks.
Clemson Cooperative Extension, Home & Garden Information Center, Mulch (HGIC 1604) (checked October 19, 2026)Fine wood and bark mulch no more than 2 to 3 in, coarse nuggets up to 4 in, 1 in of small rock for weed control, 1 cu yd covers 324 sq ft at 1 in.
Jolly Gardener, Mulch Usage Chart (checked October 19, 2026)Bagged mulch in 2 and 3 cu ft bags.
Kellogg Garden Products, Soil Building Conditioner (checked October 19, 2026)Mulch and soil amendment in 1.5, 2.5 and 3 cu ft bags, spread 2 to 3 in deep.
Kellogg Garden Products, Premium Garden Topsoil (checked October 19, 2026)Topsoil in 1 cu ft bags.
Kellogg Garden Products, All Natural Garden Soil for Flowers & Vegetables (checked October 19, 2026)Garden soil in 0.75 and 2 cu ft bags.
Kellogg Garden Products, All Natural Topper Soil for Lawns, Sod & Seed (checked October 19, 2026)Topper soil in 1.5 cu ft bags.
Kellogg Garden Products, Purely Compost (checked October 19, 2026)Compost in 1.5 cu ft bags.
Quikrete, QUIKRETE Sand & Gravel Products (data sheet, revised November 2020) (checked October 19, 2026)All-purpose sand in 50, 60 and 70 lb bags; all-purpose gravel and play sand in 50 lb bags.
Quikrete, Play Sand (product sheet) (checked October 19, 2026)A 50 lb bag holds about ½ cu ft (14 L); 16 bags for a 4 × 4 ft box at 6 in; yields allow no waste.
Quikrete, Quantity calculators: Hardscapes rocks and sands (sandbox) (checked October 19, 2026)Its sandbox calculator counts a 50 lb bag as 0.5 cu ft (square feet × depth ÷ 12 ÷ 0.5).

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