Topsoil Calculator – How Much Topsoil Do I Need?
Laying new topsoil for a garden, lawn, or raised bed? Our topsoil calculator tells you exactly how many cubic yards or bags you need based on your area size and desired depth.
Topsoil Calculator
Topsoil Depth Guide
| Purpose | Recommended Depth |
|---|---|
| Lawn Topdressing | 1–2 inches |
| New Lawn | 4–6 inches |
| Garden Beds | 6–8 inches |
| Raised Beds | 10–12 inches |
How to Calculate How Much Topsoil You Need
Topsoil is sold by volume, in cubic yards, cubic metres or bags, so the job is to turn your area and desired depth into a volume.
2. Volume in cubic feet = Area x (Depth in inches / 12)
3. Cubic yards = Cubic feet / 27
Worked example: topdressing a lawn
A lawn 30 ft by 20 ft, topdressed at half an inch:
- Area: 30 x 20 = 600 sq ft
- Depth in feet: 0.5 / 12 = 0.0417 ft
- Volume: 600 x 0.0417 = 25 cubic feet
- Cubic yards: 25 / 27 = 0.93 cubic yards
Worked example: filling a raised bed
A raised bed 8 ft by 4 ft, filled 10 inches deep:
- Area: 8 x 4 = 32 sq ft
- Depth in feet: 10 / 12 = 0.833 ft
- Volume: 32 x 0.833 = 26.7 cubic feet, which is 0.99 cubic yards
Raised beds are usually filled with a mix rather than pure topsoil: a common recipe is about 60 percent topsoil, 30 percent compost and 10 percent drainage material such as coarse sand or perlite.
How Deep Should the Topsoil Be?
| Use | Depth | Why |
|---|---|---|
| Lawn topdressing | 0.25 to 0.5 inch | Any deeper smothers existing grass |
| New lawn from seed or turf | 4 to 6 inches | Enough root zone to survive dry spells |
| Flower beds | 6 to 12 inches | Most ornamentals root in the top foot |
| Vegetable beds | 12 to 18 inches | Root crops need depth |
| Levelling dips and hollows | As needed | Fill in layers of 1 inch, not all at once |
Weight, Bags and Delivery
| Measure | Typical value |
|---|---|
| 1 cubic yard of dry topsoil | About 2,000 lb (1 ton) |
| 1 cubic yard of wet topsoil | Up to 3,000 lb |
| 1 cubic yard in 40 lb bags | About 36 to 40 bags |
| 1 cubic metre of topsoil | About 1.2 to 1.5 tonnes |
Bags are convenient for small jobs but expensive per unit volume. Anything over roughly one cubic yard is almost always cheaper delivered loose, and it saves opening forty bags by hand.
Topsoil, Garden Soil and Compost
- Topsoil is screened natural soil. It is the bulk filler: cheap, structural, and low in nutrients on its own.
- Garden soil is topsoil already blended with organic matter and sometimes fertiliser. It costs more and is meant for planting straight into.
- Compost is decomposed organic matter. It is a soil improver, not a growing medium by itself: planting directly into pure compost tends to dry out fast and can be too rich for seedlings.
For most projects the sensible approach is bulk topsoil for volume, with compost mixed into the top layer where things will actually grow.
Common Topsoil Mistakes
- Dividing cubic feet by 9 rather than 27. A cubic yard is 27 cubic feet.
- Forgetting settlement. Fresh topsoil settles 10 to 20 percent after watering and a few weeks of weather. Order a little extra and mound slightly.
- Laying topsoil over compacted ground. Break up the surface first, or you create a drainage barrier and the new soil sits in a puddle.
- Buying unscreened soil for a lawn. Unscreened soil carries stones, roots and weed seed. Screened topsoil costs a little more and saves a lot of weeding.
Frequently Asked Questions
How much topsoil do I need for my lawn?
For topdressing an existing lawn use a quarter to half an inch. A 30 x 20 ft lawn at half an inch needs about 0.93 cubic yards. For a brand new lawn from seed or turf you need a proper root zone of 4 to 6 inches, which for the same area would be about 7.5 to 11 cubic yards.
How many cubic yards of topsoil do I need?
Multiply length by width to get square feet, multiply that by the depth in feet (inches divided by 12), then divide by 27. For example, an 8 x 4 ft raised bed filled 10 inches deep is 32 x 0.833 = 26.7 cubic feet, which is about 1 cubic yard.
How much does a cubic yard of topsoil weigh?
About 2,000 lb, or roughly 1 ton, when dry. Wet topsoil is considerably heavier and can reach 3,000 lb per cubic yard, which matters when checking delivery vehicle limits or how much your wheelbarrow can realistically carry.
How many bags of topsoil are in a cubic yard?
About 36 to 40 bags of the standard 40 lb size. Bags suit small jobs, but for anything over roughly one cubic yard a bulk delivery is usually cheaper per unit volume and far less work to handle.
What is the difference between topsoil and garden soil?
Topsoil is screened natural soil used as bulk filler. It is inexpensive and structural but low in nutrients on its own. Garden soil is topsoil already blended with organic matter and sometimes fertiliser, so it costs more and is intended for planting into directly. A common approach is bulk topsoil for volume with compost mixed into the top layer.
Can I plant directly into compost instead of topsoil?
It is not ideal. Compost is a soil improver rather than a growing medium: pure compost dries out quickly, can settle heavily, and is often too rich for seedlings. Mix it into topsoil instead, at roughly 25 to 30 percent of the total volume.
Does topsoil settle after I lay it?
Yes, typically by 10 to 20 percent once it has been watered and weathered for a few weeks. Order slightly more than your calculation suggests and mound the surface a little so it settles level rather than into a dip.