Soil Calculator
Work out exactly how much soil, topsoil, or compost you need for raised beds, containers, and garden borders — no more guessing at the garden centre.
Calculate Your Soil Volume
Choose a shape, enter your dimensions and fill depth, and instantly see how much soil you need in cubic feet, cubic yards, litres, and standard bags.
Soil Volume Estimator
Get a clear breakdown of the volume and bags required to fill your space.
How it Works
Understanding your soil volume
Base Area
We calculate the footprint of your bed or container from its length and width, or diameter if circular.
Fill Depth
Your chosen depth in inches is converted to feet and multiplied by the area to get raw volume.
Settling Allowance
Loose soil compacts after watering, so we add your chosen percentage to avoid running short later.
Bag Conversion
We convert the total volume into litres and divide by your selected bag size, rounding up to a whole bag.
Recommended Fill Depths
A general guide to how deep to fill soil for common garden projects. Adjust based on what you’re growing.
| Project Type | Typical Depth | Notes |
|---|---|---|
| Lawn Top-Dressing | 0.25 – 0.5 in | A thin layer worked into an existing lawn to level dips and improve soil structure. |
| Flower Beds & Borders | 6 – 8 in | Enough depth for most annuals and perennials to establish healthy root systems. |
| Vegetable Raised Beds | 10 – 12 in | Deeper fill supports root vegetables and gives plants room for strong, unrestricted growth. |
| Container & Pot Planting | Full container depth | Fill to about 1 inch below the rim, leaving space for watering without overflow. |
| Tree & Shrub Planting | 18 – 24 in | Wider, deeper backfill around the root ball helps young trees and shrubs establish firmly. |
Soil Calculator FAQ
Answers to the most frequently asked questions about estimating and buying soil for your garden.
Multiply the length, width, and depth of your raised bed (in feet) to get cubic feet, then divide by 27 to get cubic yards. A bed measuring 4ft by 8ft filled to 12 inches deep needs roughly 32 cubic feet, or about 1.2 cubic yards, of soil.
Topsoil is the natural upper layer of earth, generally used for filling beds and levelling lawns. Potting soil is a lighter, sterile blend designed for containers and drainage. Compost is decomposed organic matter used to enrich existing soil rather than fill a large volume on its own.
Standard soil bags are commonly sold in 20L, 40L, 50L, or 2 cubic foot sizes. Once you know your total volume in litres or cubic feet, divide it by the bag size to estimate how many bags to buy, and round up to account for settling.
Yes, loose soil typically settles by around 10-20% after watering and time. Many gardeners add an extra 10% to their calculated volume, or slightly overfill beds and containers, to allow for this natural compaction.