Mulch answer guide

How much mulch do I need?

Estimate mulch quantity from bed area, target depth, top-up depth, cubic yards, bag count, bulk cost, bagged cost, and spreading labor.

Reviewed - May 27, 2026

Short answer

Multiply bed length by bed width by the number of beds, multiply that area by mulch depth in feet, then divide cubic feet by 27 to convert to cubic yards.

For two 20 ft by 6 ft beds at 3 in deep, the current calculator estimates 60.0 cu ft of mulch, 2.3 cu yd when rounded for ordering, or 30 bags if each bag holds 2 cu ft.

For top-ups, subtract the existing mulch depth from the target depth first so you only buy the missing material.

If those same two beds already have 2.5 in and the target is 3 in, the generated top-up is only 10.0 cu ft, 0.4 cu yd, or 5 two-cu-ft bags.

Use the mulch calculator

Mulch quantity method

Calculate bed area: length x width x number of beds.
For a new bed, convert mulch depth from inches to feet by dividing by 12.
For a top-up, subtract existing depth from target depth, then convert only the additional depth to feet.
If the existing depth is already equal to or greater than the target depth, the added mulch volume is zero.
Calculate cubic feet: bed area x mulch depth in feet.
Convert to cubic yards: cubic feet / 27, then round up for ordering.
If buying bags, divide cubic feet by the selected bag size and round up to a whole bag count.

Quick examples

10 ft by 10 ft bed

1.0 cu yd

One bed, 3 in depth, shredded hardwood

Two 20 ft by 6 ft beds

2.3 cu yd

3 in depth, shredded hardwood

Two 30 ft by 8 ft beds

3.0 cu yd

2 in depth, shredded hardwood

Top-up from 1 in to 3 in

1.5 cu yd

Two 20 ft by 6 ft beds, only missing depth

Light top-up from 2.5 in

0.4 cu yd

Two 20 ft by 6 ft beds, 0.5 in missing

Existing mulch already 3 in

0.0 cu yd

Target depth already met

These examples use the current U.S. default mulch assumptions: 27 cu ft per cubic yard, order cubic yards rounded up to the nearest tenth, and 2 cu ft bags. Top-up examples calculate only the missing depth and return zero when the current depth already meets the target.

Worked example

2 beds at 20 ft by 6 ft, 3.0 in deep.

Bulk mulch

2.3 cu yd

60.0 cu ft calculated volume

Bags

30 bags

2 cu ft bag size

Bed area

240 sq ft

3.0 in target depth

Buying choice

Bulk likely

Bulk material is about $20 lower before delivery fees

Bulk material total

$69–$161

Bulk mulch before delivery fees

Bagged material total

$90–$180

Alternative if buying bags

Installed total

$156–$391

Bulk material plus spreading labor

Starter shopping list

shredded hardwood mulch, bulk 2.3 cu yd
2 cu ft bags 30 bags
Edging cleanup, rake, wheelbarrow, gloves As needed

This example is generated from the same calculator logic used on the Mulch calculator page.

Depth target

A 2 in to 3 in finished depth is common for many beds, but plant type, soil, slope, and local climate can change the right target.
Keep mulch thinner near trunks, stems, siding, and weep holes instead of applying the same depth everywhere.

Bulk or bags

Use cubic yards when pricing bulk mulch and bag count when buying from a retail shelf.
Compare bulk and bagged options by volume, then add delivery fees, minimum orders, and the time needed to move material from the drop point.

Top-up depth check

Measure the remaining mulch depth in a few spots before ordering, because faded color does not always mean the bed is short on depth.
For refresh projects, calculate only the missing depth; a half-inch top-up can be a small bag job even when a full new layer would be bulk-size.

Bed shape

For curved beds, split the area into rectangles or use a measured square-foot area before applying the depth formula.
Subtract large patios, boulders, trunks, and dense plant clusters when they materially reduce the area receiving mulch.

Common mistakes

Using inches directly in the volume formula instead of converting depth to feet.
Refreshing an existing bed from full target depth instead of only the missing top-up depth.
Comparing bag price with bulk price without converting both to cubic feet or cubic yards.
Forgetting delivery fees, minimum orders, wheelbarrow distance, edging cleanup, and bed prep.
Buying another full layer when the existing mulch is faded but still close to the target depth.
Piling mulch against trunks, stems, siding, weep holes, or foundation details.

FAQ

How do I calculate how much mulch I need?

Multiply bed length by width by bed count, multiply by depth in feet, then divide cubic feet by 27 for cubic yards. For bags, divide cubic feet by the bag size and round up.

How many cubic yards of mulch do I need for two 20 by 6 beds?

At 3 in deep, two 20 ft by 6 ft beds need 60.0 cu ft of mulch. The generated example rounds that to 2.3 cu yd for bulk ordering.

How many bags of mulch do I need?

Divide the calculated cubic feet by the bag size. For the two-bed generated example, 60.0 cu ft divided by 2 cu ft per bag equals 30 bags.

How do I estimate mulch for a top-up?

Subtract the existing mulch depth from the target finished depth, then calculate volume from the additional depth only. If the bed already meets the target depth, you may only need to rake and refresh.

How much mulch for a half-inch top-up on two 20 by 6 beds?

Two 20 ft by 6 ft beds total 240 sq ft. A 0.5 in top-up needs 10.0 cu ft of mulch, which rounds to 0.4 cu yd or 5 bags at 2 cu ft per bag.

What if the existing mulch already meets the target depth?

Do not add volume just because the color has faded. In top-up mode, matching the existing depth to the target returns 0.0 cu yd and 0 bags, so rake, spot fill, or refresh color only where needed.

Is bulk mulch cheaper than bagged mulch?

Bulk is often cheaper for medium and large beds, but delivery fees and minimum orders can change the better choice. Small top-ups may be easier and cheaper with bags.