Topsoil & Raised-Bed Soil Calculator
Enter the length, width and fill depth of each bed and this calculator tells you exactly how much soil to buy — the number of bags, the order in cubic yards and cubic feet, the estimated weight, and the cost. Everything runs in your browser; nothing you type leaves your device.
It is built for garden soil specifically. Pick a soil type (topsoil, compost, raised-bed or potting mix, peat, coco coir, vermiculite, perlite or composted manure) and it pre-fills a typical density and bag size; tap a fill-depth chip for a standard, shallow or deep bed, a new-lawn base or a top-dress; use the fill-to helper to leave a gap below the rim; and — the part most calculators skip — break your total order down into a per-ingredient soil-mix shopping list. Every number stays editable.
Add a bed for each area and the totals update live. Switch between metric and imperial at any time and every value converts in place, or use Coverage mode to work backwards from soil you already have.
How to use the topsoil calculator
Soil volume is a footprint area multiplied by a fill depth. You can mix units — measure the bed in feet and set the depth in inches — and the calculator handles the conversion, which is the step most people get wrong by hand.
Choosing a soil type only sets sensible defaults for density and bag size; it never changes the filled area or the volume, because volume is pure geometry. Ordering a soil mix? Set the ratio in the mix panel and the same order volume is split into per-ingredient quantities.
How to calculate soil for a raised bed in 5 steps
- Choose unitsPick metric (m, mm, m³) or imperial (ft, in, yd³) at the top. You can switch later and every entry converts in place.
- Pick a soil typeChoose topsoil, compost, raised-bed or potting mix, peat, coir, vermiculite, perlite or composted manure to pre-fill a typical density and bag size. The type changes only the weight and bag convention, never the filled volume — every value stays editable.
- Set the fill depthTap a fill-depth chip — raised bed 12 in, shallow 6 in, deep 18 in, new-lawn base 4 in or top-dress 1.5 in — or type your own. Turn on the fill-to helper to fill to a set gap below the rim. Chips fill any empty bed depths without overwriting depths you have typed.
- Add your bedsAdd a bed per area, choose its shape (rectangle, round bed or a direct area) and enter the dimensions. Totals sum across every bed.
- Read the resultsThe panel shows bags and order volume as the two headline numbers, plus cubic feet, estimated weight, truckloads and cost. Open the mix panel to split the order into ingredients. Enter both a bag price and a bulk price to see which is cheaper, then export CSV or print a plan.
Worked example: a 4 × 8 ft bed, 12 in deep
The classic question is “how much soil for a 4 by 8 raised bed?”. Convert the depth to feet first, multiply by the footprint, then divide by 27 — there are 27 cubic feet in a cubic yard — or divide the cubic feet by the bag size to count bags. Filling to 12 in inside a 14 in bed leaves a 2 in freeboard gap below the rim so the soil has room to settle.
4 ft × 8 ft × 12 in = 1.19 yd³ (32 ft³ · 43 bags of 0.75 cu ft)
- Footprint area: 4 ft × 8 ft = 32 ft²
- Fill depth in feet: 12 in ÷ 12 = 1 ft
- Cubic feet: 32 ft² × 1 ft = 32 ft³
- Cubic yards: 32 ft³ ÷ 27 = 1.19 yd³
- Bags: 32 ft³ ÷ 0.75 = 43 bags (round up)
Split your order into a soil-mix shopping list
A raised bed is rarely one material. Pick a blend — 100% topsoil, a topsoil/compost mix, a three-part raised-bed blend or Mel's Mix — and the calculator splits the exact same order volume above into a per-ingredient shopping list: how much of each ingredient, in cubic yards and cubic feet, and how many bags of each. The proportions stay editable, so you can dial in your own recipe.
One thing that looks odd but is correct: each ingredient is bought as its own product and its bags are rounded up on their own, so the per-ingredient bag counts do not add up to the single-material bag total — a mix is several separate SKUs, not one.
| Ingredient | Volume (yd³) | ft³ | Bags |
|---|---|---|---|
| Topsoil | 0.71 | 19.2 | 26 |
| Compost | 0.36 | 9.6 | 10 |
| Perlite | 0.12 | 3.2 | 1 |
A 1.19 yd³ raised-bed blend splits into topsoil, compost and perlite — priced and bagged separately.
How fill depth changes what you order
Depth is the biggest lever on a soil order: going from a shallow 6 in bed to a deep 18 in bed triples the volume and the number of bags for the same footprint. Six inches suits shallow-rooted greens, twelve inches is the all-round standard for most vegetables, and eighteen inches gives deep-rooted crops room — but each extra inch is more soil to buy and haul.
How much does a yard of soil cover?
Coverage is pure geometry: one cubic yard is 27 cubic feet, so spread at a given depth it covers 324 ÷ depth-in-inches square feet — the same whichever soil you choose. Use this table to sanity-check an order, to size a new-lawn base or a top-dress, or to estimate the depth a fixed amount will give you.
| Fill depth | Covers (ft²) | Covers (m²) |
|---|---|---|
| 1.5 in | 216 | 20.1 |
| 4 in | 81 | 7.5 |
| 6 in | 54 | 5.0 |
| 12 in | 27 | 2.5 |
Frequently asked questions
How much soil do I need for a raised bed?
Multiply the bed's length by its width by the fill depth. A 4 × 8 ft bed filled 12 in deep needs 32 cubic feet — about 1.2 cubic yards, or 43 bags of 0.75 cu ft topsoil. Enter the dimensions (you can use feet for the bed and inches for the depth) and the calculator does the conversion, adds your waste allowance and totals every bed into one order in bags, cubic yards and cubic feet.
How many bags of soil are in a cubic yard?
Divide 27 cubic feet by the bag size: a 0.75 cu ft topsoil bag is 36 per cubic yard, a 1 cu ft compost bag is 27, and a 1.5 cu ft raised-bed mix bag is 18. The calculator counts bags by rounding your exact order up to whole bags for the bag size you pick, so allow a little for settling.
How deep should a raised bed be?
Twelve inches is the all-round standard — deep enough for most vegetables, shallow enough to stay affordable to fill. Six inches suits shallow-rooted greens like lettuce, and 18 to 24 inches gives deep-rooted crops such as tomatoes and carrots room to grow. For a new lawn, add about 4 inches of topsoil over the subsoil; for a top-dress over an existing bed, an inch or two is plenty.
What soil mix should I use for a raised bed?
A common recipe is roughly 60% topsoil, 30% compost and 10% an aeration ingredient such as perlite or vermiculite; a simpler 70/30 topsoil-to-compost blend is also widely recommended. Some gardeners prefer a heavier 40/40/20 mix with more compost. Pick a preset in the mix panel and edit the ratios to taste — the calculator splits your order into how much of each ingredient to buy.
What is Mel's Mix?
Mel's Mix, from Square Foot Gardening, is equal parts by volume of compost, peat moss (or coco coir) and coarse vermiculite — one third each, with no topsoil at all. It is light, drains well and holds moisture. Choose the Mel's Mix preset and the calculator splits your order into the three ingredients and counts the bags of each.
How far below the rim should I fill a raised bed?
Leave roughly 1 to 2 inches of gap below the rim. Soil settles and compacts after watering, so a bed filled level to the top overflows once it beds in, and the gap leaves room for a mulch layer. Turn on the fill-to helper, enter your bed's wall height and the gap you want, and the calculator sets the fill depth for you — so you don't order soil right to the rim.
Should I buy soil in bags or in bulk?
Bags are convenient for one or two beds and easy to carry; bulk (by the cubic yard, delivered) is usually cheaper once a job runs to many bags — a standard dump truck delivers about 12 cubic yards. Enter a bag price and a bulk price and the calculator shows both totals, tells you which is cheaper and by how much, and can show the break-even volume where bulk overtakes bags.
How much area does a yard of soil cover?
It depends only on depth: one cubic yard covers 324 ÷ depth-in-inches square feet. That is about 27 ft² at 12 in, 54 ft² at 6 in, 81 ft² at 4 in and 216 ft² at 1.5 in — the same for any soil. Switch to Coverage mode to enter a volume or a number of bags and read the area covered directly.
Does it work in metric and imperial?
Both. Switch units at the top and every dimension, volume, weight and price converts in place — depths in inches or millimetres, volume in cubic yards or cubic metres, bags in cubic feet or litres. You can measure a bed in feet and set the depth in inches; the calculator handles the mix.
Is the calculator private?
Yes. Every calculation runs entirely in your browser. Nothing you enter is sent to any server, and your project is saved only in your own browser's local storage.