Compost Calculator

Use this compost calculator to work out how much compost you need for a garden bed, a raised bed or a lawn. Enter the area, pick what you are working on and we fill in a sensible depth, or set your own. You get the volume in cubic yards and cubic feet (or cubic metres and litres), an approximate weight, the number of bags and an optional cost.

H

Creator

Haali

Updated October 2026

Calculate your compost

Results update as you type

Units
Area to cover
Total area
Length
Width
Garden or lawn type
Depth
Bag size
Price (optional)

You need about

Area
Approx. weight
Estimated cost

Enter your measurements above to see how much compost to order.

See all calculators
Related: Mulch Garden soil Raised bed soil Topsoil

How to use the compost calculator

Choose US or Metric units.
Enter the total area in square feet (or m²), or switch to Length × width and enter the size of a rectangular bed. For several beds, add their areas together and enter the total.
Pick your job under Garden or lawn type. This fills in a typical depth for a garden, raised bed, new lawn or established lawn. Choose Custom depth to type your own in inches or centimetres.
Pick a bag size: 1, 1.5 or 2 cubic feet in US units, or 50 litres in metric.
Optionally add a price per cubic yard (per m³ in metric) or per bag to see the total cost.

The result shows the volume for an even layer, plus the area, an approximate weight, how many bags to buy (rounded up to whole bags) and the same volume in cubic feet or litres. It does not add extra for waste, so if you are close to the next whole bag, buy that one.

How much compost do I need?

The amount depends on the area and how thick a layer you spread. Pure compost is too rich to plant straight into, so for pots and new beds aim for a mix of about one part compost to three parts soil. For spreading on beds or lawns, these are the depths the calculator uses:

Garden or raised bed, light top-up 1 in (2.5 cm)
Garden or raised bed, poor soil 2 in (5 cm)
New lawn, dug into the top 6 to 8 in (15 to 20 cm) 1 to 2 in (2.5 to 5 cm)
Established lawn, top dressing after aerating ¼ to ½ in (0.6 to 1.3 cm)

Compost for a raised bed

Measure the inside length and width of each bed. When you are topping up, only the surface area matters, not how tall the bed is. Choose Raised bed, light for a yearly top-up or Raised bed, heavy for tired or poor soil. If you are filling a new raised bed from empty, you need a full soil mix rather than a compost layer, and the raised bed soil calculator is built for that.

Top dressing a lawn with compost

For an established lawn, spread a thin layer after aerating so it works down into the holes. On a 1,000 sq ft lawn, a ¼ inch top dressing takes 0.77 cubic yards (about 14 bags of 1.5 cu ft), and ½ inch takes 1.54 cubic yards.

How does the calculation work?

Multiply the area by the depth, with both in the same units.

Cubic feet = area (sq ft) × depth (in) ÷ 12

Cubic yards = cubic feet ÷ 27

Cubic metres = area (m²) × depth (cm) ÷ 100

One cubic metre is 1,000 litres.

Raised bed, 8 × 4 ft, 2 inches deep: 32 sq ft × 2 ÷ 12 = 5.3 cubic feet, or 0.2 cubic yards. That is 4 bags of 1.5 cu ft or 3 bags of 2 cu ft, weighing about 200 lb.

New vegetable bed, 3 m by 1.5 m, poor soil: 4.5 m² × 0.05 m = 0.23 m³. That is about 230 litres, or 5 bags of 50 L.

Established lawn, 30 m by 25 m: 750 m² × 0.013 m = 9.75 m³. At that size, a bulk delivery makes far more sense than bags.

Compost coverage

How far compost goes depends only on the depth. One cubic yard (27 cubic feet) covers:

¼ in deep 1 cubic yard covers 1,296 sq ft, a 1.5 cu ft bag 72 sq ft
½ in deep 1 cubic yard covers 648 sq ft, a 1.5 cu ft bag 36 sq ft
1 in deep 1 cubic yard covers 324 sq ft, a 1.5 cu ft bag 18 sq ft
2 in deep 1 cubic yard covers 162 sq ft, a 1.5 cu ft bag 9 sq ft

In metric, 1 m³ (1,000 litres) covers 40 m² at 2.5 cm, and a 50 L bag covers 2 m².

Converting cubic yards, cubic feet and litres

1 cubic yard = 27 cubic feet = about 765 litres. That is 18 bags of 1.5 cu ft, 13.5 bags of 2 cu ft or 27 bags of 1 cu ft. 1 m³ = 1,000 litres = 35.3 cubic feet = 1.31 cubic yards.

Buying compost: bulk or bags

Bagged compost suits small beds and top-ups. In the US it is often sold in 1, 1.5 or 2 cubic foot bags; elsewhere 40 or 50 litre bags are common. For bigger jobs, suppliers sell it loose by the cubic yard or cubic metre, or in one cubic metre bulk bags.

Price varies with the supplier, what the compost is made from and how much you buy. Enter your own price in the calculator to see the total for bags or bulk. For anything over about a cubic yard, ask for a bulk quote.

How much does a yard of compost weigh?

The calculator estimates weight using a typical density for compost, which works out to about 1,020 lb per cubic yard, roughly half a US ton. Real weight varies with moisture and what the compost is made from, and wet compost is noticeably heavier. A 50 L bag weighs roughly 25 to 35 kg (55 to 75 lb), so check what your car or trailer can carry.

Why add compost?

Compost does not just feed plants. It changes how the soil behaves.

Adds slow release nutrients, so you need less bought fertiliser.
Loosens heavy clay and helps sandy soil hold on to water.
Feeds the worms and microbes that keep soil healthy.
Improves drainage and cuts down on puddles and runoff after rain.

What is compost?

Compost is plant material that has rotted down into a dark, crumbly soil improver. Leaves, peelings, grass and prunings go in. After a few months of bacteria, fungi and worms doing their work, you get something that smells like a forest floor and feeds whatever you grow in it.

Planning the rest of the job? Use the Mulch calculator and the Garden soil calculator too.

Making compost at home

A compost bin turns kitchen and garden waste into free soil improver and keeps it out of the rubbish. A pile in a shady corner works. So does a closed bin on a balcony.

What can go in

Garden waste

Dry leaves, grass clippings and soft prunings. Chop woody stems small.

Good for bulk and air

Kitchen scraps

Fruit and vegetable peelings, eggshells, coffee grounds and tea leaves.

Good for nitrogen

Paper and card

Plain, torn into small pieces. Helps balance wet green waste.

Good for carbon

Leave out

Meat, fish, dairy, oils and cooked food. They smell and attract pests.

Keep these in the bin

Compost calculator questions

Can I use this calculator for pots?

It works out a layer spread over an area, not the volume of a container. For pots, mix about one part compost to three parts potting soil, and use the potting mix calculator to find how much fills each pot.

Can I use compost instead of soil?

Compost is a soil improver rather than a replacement for soil. Mix it into your existing soil or topsoil, at about one part compost to three parts soil for new beds. If you need to fill a bed or raise a level, work out the soil first and add compost on top of that.

Does the calculator add extra for waste?

No. It gives the exact volume for an even layer and only rounds bags up to whole bags. If the ground is uneven or you are close to the next bag, buy a little more.

How do I calculate compost for several beds?

Measure each bed, multiply length by width for each one, add the areas together and enter the total in Total area.

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