How deep should mulch be?

A 5-8 cm layer of mulch is ideal for suppressing weeds and retaining moisture. Anything deeper can suffocate roots and create waterlogging problems.

How much topsoil do I need for a raised bed?

A standard raised bed (1.2m x 2.4m x 0.3m deep) needs approximately 0.86 cubic metres, or around 860 litres of topsoil. Mix with 20-30% compost for best results.

What is the difference between topsoil and compost?

Topsoil is mineral-based soil used for structure and filling. Compost is decomposed organic matter used to enrich existing soil with nutrients. Most gardens benefit from a blend of both.

How heavy is a cubic metre of soil?

Topsoil weighs approximately 1,200 kg per cubic metre. Compost is lighter at around 550 kg per cubic metre. Gravel is heavier at about 1,800 kg per cubic metre.

Can I use this calculator for a circular garden bed?

Calculate the equivalent rectangular area first (pi x radius x radius), then enter that as length x width. For a 2m diameter circle, that is approximately 3.14 square metres.

How deep should topsoil be for a garden bed?

A minimum depth of 15 to 20 cm (6 to 8 inches) is recommended for most flowers and vegetables. Deep-rooted plants like tomatoes and carrots benefit from 30 cm (12 inches) or more.

What is the difference between topsoil and compost?

Topsoil is the upper layer of natural soil, providing structure and drainage. Compost is decomposed organic matter that adds nutrients. For garden beds, a 70/30 mix of topsoil and compost is ideal.

How much does garden soil weigh?

Topsoil weighs approximately 1,000 to 1,300 kg per cubic metre when dry. Wet soil can weigh up to 1,700 kg per cubic metre. Compost is lighter at about 400 to 600 kg per cubic metre.

How do I convert cubic metres to litres for bags?

1 cubic metre equals 1,000 litres. Most retail bags are 25 to 50 litres, so 1 cubic metre equals 20 to 40 bags depending on bag size.

Should I use mulch on top of soil?

Yes. A 5 to 10 cm layer of mulch retains moisture, suppresses weeds, and regulates soil temperature. Organic mulches (bark, straw) also break down and add nutrients over time.

Last updated: 28.03.2026

Garden Mulch & Soil Volume Calculator

Calculate exactly how much topsoil, compost, mulch, gravel or sand you need. Enter area dimensions and depth to get cubic metres, litres and estimated...

Calculate Soil VolumeUpdates instantly

Enter your garden bed dimensions and material type to get the volume and estimated weight.

Volume needed

1.08m³

1080 litres

Area

3.6 m²

Depth

30 cm

Est. weight

1296 kg