Leaf Mulch Calculator

Every fall, trees hand you a free supply of mulch, and most people bag it up for the curb. This leaf mulch calculator tells you how much a bed needs, in cubic yards and cubic feet, and how many 30-gallon leaf bags of shredded leaves that equals, so you know whether the leaves already in your yard are enough or whether you need to gather more. It works in square feet and inches, like the other tools on the site.

Leaves make an excellent mulch. They suppress weeds, hold moisture, protect roots from winter freeze and thaw, and break down into soil-building organic matter, all at no cost. The trick is knowing how much you need and how to prepare the leaves so they help your plants and do not smother them.

How to use the leaf mulch calculator

1. Enter the area you want to mulch in square feet. For a rectangle, multiply length by width. For several beds, add their areas together.
2. Enter the depth in inches. Two to 4 inches is the normal range for leaf mulch. Use the lower end around small plants and the upper end for winter protection or weed control on paths.
3. Read the result. The calculator shows the cubic yards needed, the cubic feet and the number of 30-gallon bags of shredded leaves that fills the volume.

The bag count assumes a standard 30-gallon leaf bag, which holds about 4 cubic feet. The figures describe the finished layer, so if you are collecting whole leaves, which are fluffier than shredded ones, you will gather more than the bag count suggests and then watch them settle.

The leaf mulch math

Leaf mulch is calculated like any other mulch: area times depth gives volume. Depth is in inches, so it is divided by 12 to convert to feet.

Cubic feet = area (sq ft) × depth (in) ÷ 12
Cubic yards = cubic feet ÷ 27
30-gallon bags = cubic feet ÷ 4.01

A 30-gallon bag holds 30 × 231 = 6,930 cubic inches, which is 4.01 cubic feet. That is why the calculator divides by 4.01.

Worked example: a large garden bed area

You want to mulch 500 square feet of beds with 3 inches of shredded leaves. The volume is 500 × 3 ÷ 12 = 125 cubic feet, which is 125 ÷ 27 = 4.6 cubic yards. In 30-gallon bags that is 125 ÷ 4.01 = 31.2, so you need 32 bags of shredded leaves.

Worked example: a border along a fence

A border 20 feet long and 4 feet wide gets a 2 inch layer. The area is 80 square feet, and the volume is 80 × 2 ÷ 12 = 13.3 cubic feet, or 0.49 cubic yards. That is 13.3 ÷ 4.01 = 3.3, so plan on 4 bags.

Worked example: vegetable garden paths

Paths between raised beds total 100 square feet, and you want a thick 4 inch layer to suppress weeds. The volume is 100 × 4 ÷ 12 = 33.3 cubic feet, which is 1.2 cubic yards or about 8.3 bags, so gather 9 bags of shredded leaves.

Coverage per cubic yard

If you are comparing leaf mulch with bulk deliveries of wood mulch, it helps to know how far a cubic yard goes. One cubic yard is 27 cubic feet, and the area it covers depends on depth:

• 2 inch layer: about 162 square feet
• 3 inch layer: about 108 square feet
• 4 inch layer: about 81 square feet

Settling matters with leaves. Shredded leaves compact over the first few weeks and continue to break down through the season, so a 4 inch layer in fall often thins to 2 or 3 inches by spring. Many gardeners deliberately lay it on a little thick in fall to allow for this.

How many leaves will you have?

It is hard to predict exactly, because it depends on the tree species, its age and size and how many trees drop leaves into your yard. A single large mature tree can easily produce enough leaves to fill dozens of bags. For most suburban yards, the leaves available in fall exceed what the beds need once the leaves are shredded, so the limiting factor is more often time and effort than supply.

Shredding also changes the numbers dramatically. Shredded leaves take up a small fraction of the space of whole leaves, and gardeners often cite a reduction to roughly a tenth of the original volume, although the exact figure depends on the leaf type and how finely they are chopped. That is why a pile that looks overwhelming can turn into a manageable stack of bags.

How to shred leaves

Shredding is the single most useful step, because it stops leaves from matting into a wet, slimy layer that blocks air and water. You do not need special equipment.

• Mow over them. Run a mulching mower or a mower with a bagger over dry leaves on the lawn. This is the easiest method, and it fills your bags directly.
• Use a string trimmer in a bin. Put leaves in a tall trash can and run a string trimmer in it. It is messy but fast for small amounts.
• Use a leaf shredder or blower-vac. Many blower-vacuums shred as they collect, and standalone leaf shredders handle bigger piles.

Dry leaves shred better than wet ones. If it has rained, wait a day or two for the leaves to dry, or rake them onto a tarp to dry first.

Whole leaves or shredded?

Whole leaves work in some places. Large, loose leaves like oak and maple can be left whole in the back of a shrub border or under trees where the layer will not smother anything. Left whole, they tend to mat when wet, especially broad maple leaves, which can form a dense, water-shedding sheet. Shredded leaves stay loose, let rain through and break down more evenly. For vegetable and flower beds, shredded is the safer choice.

Where to use leaf mulch

• Flower and shrub beds: a 2 to 3 inch layer holds moisture and suppresses weeds. Keep it a few inches back from stems and trunks.
• Vegetable beds: spread shredded leaves between rows and over empty beds in fall. They protect the soil over winter and add organic matter when they break down. In spring, rake them aside before planting or work them into the top of the bed.
• Garlic and overwintering crops: a blanket of shredded leaves is a classic cover for garlic. The guide to planting garlic in fall covers the details.
• Paths: a thick layer of leaves makes a soft path and keeps weeds down between beds. Top it up as it breaks down.
• Tree rings: leaves work as a ring around young trees. Keep the mulch a few inches away from the trunk, never piled against the bark.
• Perennial protection: a layer of leaves after the ground has cooled can help buffer freeze and thaw cycles around perennials. Avoid heavy layers on top of plants that keep green leaves in winter, because whole leaves can hold moisture against them and cause rot.

How deep should leaf mulch be?

Two to 4 inches is the usual range. A thinner layer of about 2 inches is enough for beds with small plants and seedlings, and 3 to 4 inches works for winter protection, paths and weed control. Thicker layers can block water and air, and a very deep layer of whole leaves can smother the plants beneath. Always keep leaves off the crowns of plants and a few inches away from stems and tree trunks, where moisture can cause rot and give pests cover.

For a more general guide to depth and bag counts with other mulch types, use the mulch calculator or the mulch bag calculator.

Making leaf mold

If you have more leaves than your beds can use, turn the rest into leaf mold, a dark, crumbly soil conditioner that holds water and feeds soil life. It is almost free and very easy:

1. Shred the leaves if you can, which speeds things up.
2. Pile them in a wire bin, a simple ring of fencing or a mesh bag. A pile around 3 feet across is a good size.
3. Wet the leaves as you add them so the pile is as damp as a wrung-out sponge.
4. Leave the pile alone. Turn it occasionally if you like, but it is not necessary.

Shredded leaves can turn into usable leaf mold in roughly six months to a year, and whole leaves often take a year or two. The finished product is dark, crumbly and smells earthy. Use it as a mulch, dig it into beds or mix it into potting soil. You can work out how much you will need for a bed with the soil calculator.

Using leaves in your compost pile

Leaves are a “brown” material, rich in carbon, and a good compost pile needs both browns and greens such as kitchen scraps and grass clippings. Many composters aim for roughly two to three parts brown to one part green by volume, and a stockpile of fall leaves lets you balance green material all year. Store extra bags of leaves beside the compost bin and add a layer whenever you add food scraps. The beginner’s guide to composting explains the balance in more detail, and the compost calculator works out how much finished compost you can expect to need.

Leaves to handle with care

Most leaves make good mulch, but a few need extra thought.

• Diseased leaves: leaves with fungal problems such as black spot on roses, apple scab or tomato blight can carry spores through winter. Bag them for municipal yard waste collection or compost them in a hot pile, rather than mulching the same plants.
• Black walnut leaves: black walnut produces a compound called juglone, which some plants such as tomatoes tolerate poorly. It is most concentrated in roots and nut hulls. To be safe, compost walnut leaves for a good while before using them near sensitive plants.
• Oak leaves: oak leaves are tough and slow to break down, but they have little lasting effect on soil pH once they decompose. Shred them well, and they make excellent mulch and leaf mold.
• Leaves treated with chemicals: if you have used herbicides on your lawn, check the label for any restrictions on using the clippings or leaves as mulch.

When to apply leaf mulch

Leaf mulch can go down as soon as leaves fall, but timing varies by purpose. For weed control and moisture, spread it any time the soil is clear. For winter protection of perennials and garlic, many gardeners wait until the soil has cooled and the first frosts have arrived, so plants are fully dormant and the mulch is not giving mice and voles a warm place to nest. Whichever you choose, finish before the ground freezes hard, so the mulch can do its job. Our fall garden prep guide puts mulching in the context of the other end-of-season jobs.

Leaf mulch compared with store-bought mulch

Wood chips and bagged bark are tidy and long-lasting, and they are the usual choice for front beds where looks matter. Leaf mulch is cheaper, breaks down faster and feeds the soil more quickly, which suits vegetable gardens, back borders and wooded areas. Because it breaks down in a season or two, you need to replenish it every year, but the leaves arrive free each fall to do exactly that. Many gardeners use both, with wood chips on show beds and leaves on the working parts of the garden.

Common leaf mulch mistakes

• Using whole leaves on small plants. Wet whole leaves mat down and can smother seedlings and low plants. Shred them first.
• Piling leaves against stems and trunks. This holds moisture against the bark and invites rot and pests. Leave a gap.
• Making the layer too thick. Deep layers of whole leaves block air and water. Stay within 2 to 4 inches.
• Mulching with diseased leaves. Bag leaves from visibly diseased plants and keep them out of the beds.
• Forgetting to allow for settling. Leaves compress over winter, so apply a bit more than your final target depth.
• Burying lawn grass. A thick layer of whole leaves can smother turf over winter. Shred them, and keep the layer thin enough that you can still see grass through it.

Frequently asked questions