🌿 Mulch Calculator

How to Calculate Mulch

Mulch is sold by the cubic yard (bulk delivery) or in bags (typically 2 cu ft). Knowing the right amount saves money and prevents over- or under-buying.

Basic Formula

Step by Step

• Measure the area: Length × width in feet
• Choose a depth: 2–4 inches is standard for most landscaping
• Calculate volume: Area × depth (in feet) = cubic feet
• Convert to cubic yards: Divide cubic feet by 27
• For bags: Divide cubic feet by the bag size (2 or 3 cu ft)

Recommended Mulch Depth

• 2 inches: Annual flower beds, around delicate plants
• 3 inches: Most landscape beds, trees, and shrubs (recommended)
• 4 inches: Heavy weed suppression, pathways, and play areas

Bulk vs. Bagged Mulch

For large areas, buying in bulk (by the cubic yard) is significantly cheaper — often 2–3× less per cubic foot compared to bagged mulch.

• Bagged mulch: $3–6 per 2 cu ft bag (~$40–80 per cubic yard)
• Bulk mulch: $20–45 per cubic yard delivered
• Breakpoint: If you need more than 3 cubic yards, bulk is almost always worth it

One cubic yard covers about 108 square feet at 3 inches deep, or about 13.5 standard bags.

Mulch Coverage by Depth

The number to remember is one cubic yard covers 100 sq ft at 3 inches (108 to be exact). Everything else scales from there — halve the depth, double the coverage.

Choosing a Mulch Type

Shredded hardwood is the default for a reason — it knits together and stays put on a slope where nuggets would wash into the lawn. If your beds are flat and you'd rather mulch less often, nuggets last considerably longer.

Dyed mulches are usually recycled wood with colorant. The dye itself is generally harmless, but the underlying wood can be construction debris, so buy from a supplier you trust if it's going near a vegetable garden.

How to Apply Mulch

1. Weed the bed first. Mulch suppresses seeds but won't kill established weeds — they'll push straight through.
2. Edge the bed. A cut edge 3–4 inches deep gives the mulch somewhere to stop and keeps it out of the lawn.
3. Skip the plastic sheeting. It blocks water and air, and mulch on top of it slides. Landscape fabric is better but still degrades over a few years — in beds you'll be replanting, bare soil under mulch works best.
4. Rake the old mulch loose before topping up. Compacted old mulch can form a crust that sheds water away from the roots.
5. Spread to a consistent depth — 3 inches for most beds. Measure with a stick rather than eyeballing it.
6. Keep it off the trunks. Pull mulch back 3–6 inches from tree trunks and plant stems.
7. Water it in. This settles the mulch and stops light material blowing around.

Mistakes to Avoid

• "Mulch volcanoes." Piling mulch against a tree trunk traps moisture against the bark, invites rot and rodents, and encourages roots to grow into the mulch instead of the soil. It's the single most damaging mulching habit — keep a clear ring at the base.
• Going deeper than 4 inches. Too much mulch suffocates roots and keeps water from reaching the soil at all.
• Mulching too early in spring. Mulch insulates, so a thick layer on cold soil keeps it cold. Wait until the ground has warmed.
• Using fresh wood chips on planted beds. Undecomposed wood pulls nitrogen from the soil surface as it breaks down. Fine on paths, not around annuals.
• Forgetting to account for settling. Fresh mulch settles roughly 20% in the first season, which is why beds look thin by autumn.

Measuring irregular beds? The square footage calculator handles L-shapes and circles.

Frequently Asked Questions

How deep should mulch be?

3 inches is the standard recommendation for most landscape beds. Use 2 inches for annual flower beds and 4 inches for pathways or heavy weed control. Don't exceed 4 inches — too much mulch can suffocate plant roots.

How many bags of mulch in a cubic yard?

One cubic yard equals 27 cubic feet. That's 13.5 bags of 2 cu ft mulch, or 9 bags of 3 cu ft mulch.

How much does mulch weigh?

A cubic yard of mulch weighs approximately 400–800 lbs depending on the type and moisture content. Dry wood mulch is lighter; wet or rubber mulch is heavier.

When is the best time to mulch?

Late spring (after the soil has warmed) is ideal. You can also mulch in fall to insulate plant roots over winter. Refresh mulch annually as it decomposes.

How much area does a cubic yard of mulch cover?

About 108 square feet at 3 inches deep — the figure most people round to 100. At 2 inches it covers 162 sq ft, and at 4 inches only 81.

How many bags of mulch do I need for 100 square feet?

At the standard 3-inch depth, 12–13 bags of 2 cubic foot mulch, or about 9 bags of 3 cubic foot. Each 2 cu ft bag covers roughly 8 square feet at that depth.

Is bulk mulch cheaper than bags?

Substantially — often 2–3× cheaper per cubic foot. Bagged runs roughly $40–80 per cubic yard equivalent; bulk delivered is $20–45. The crossover is around 3 cubic yards, above which bulk almost always wins even after delivery.

Should I put landscape fabric under mulch?

Usually not. Plastic sheeting is actively harmful — it blocks water and air. Landscape fabric is better but breaks down in a few years and makes replanting awkward, while weeds happily root in the mulch layer above it anyway. In beds you'll be replanting, mulch straight onto bare weeded soil.

Should I remove old mulch before adding new?

Not usually — it breaks down into the soil, which is part of the point. Just rake the old layer loose to break any water-shedding crust, then top up to your target depth. Only remove it if the bed is already at 4 inches or the mulch is matted or mouldy.

What is a mulch volcano and why is it bad?

It's mulch piled in a cone against a tree trunk. It traps moisture against bark that isn't built to stay wet, causing rot, inviting rodents and insects, and encouraging girdling roots to grow into the mulch instead of the soil. Keep mulch 3–6 inches clear of any trunk — a flat doughnut, never a cone.

Does mulch attract termites?

Mulch doesn't attract termites in itself, but a damp mulch bed piled against a house's siding or foundation gives them cover and a moisture bridge. Keep mulch at least 6 inches from siding and below the level of any weep holes or siding line.

How often should I replace mulch?

Top up annually in most climates. Organic mulch loses about 1 inch a year to decomposition, and fresh mulch settles roughly 20% in its first season — which is why a bed mulched in spring often looks thin by autumn.