Raised bed soil and gravel calculator
Type the size of your beds, borders or paths and how deep you want to fill them. We work out the litres, how many bags to buy and roughly what a bulk load would weigh.
How much to fill it
Measure the inside of each bed, or the area of a border, path or patio. Add as many as you are filling to the same depth.
0.86 m³, which is 864 litres
That fills 2.88 m² to 30 cm deep. Bags are rounded up to whole bags.
| Material | Bags of 60 litres | Loose, by weight | Typical weight |
|---|---|---|---|
| Topsoil | 15 | 1.12 to 1.30 tonnes | 1.3 to 1.5 t per m³ |
| Compost | 15 | 0.39 to 0.65 tonnes | 0.45 to 0.75 t per m³ |
| Bark (chips or mulch) | 15 | 0.22 to 0.35 tonnes | 0.25 to 0.4 t per m³ |
| Gravel or shingle | 15 | 1.30 to 1.47 tonnes | 1.5 to 1.7 t per m³ |
Weights are ranges because the same material is heavier wet than dry, and coarse gravel packs differently from fine. Use them to judge a bulk bag or a delivery, and ask the supplier for the weight of their own product.
Soil and compost settle once they are watered in, so many gardeners buy a little over and top up later.
If this is a lawn: 4 rolls of turf at 1 m² a roll, with 5% extra for cutting round edges. Turf has no depth, so the depth above does not change this.
How to use it
Measure the inside of each bed, wall to wall. Add every area you're filling to the same depth: three raised beds, or a path and a patio. Circles need only the width across. Then type the depth and pick the bag size you are buying. Your setup stays in the link, so you can take it to the garden centre on your phone.
How to read it
The top line is the space to fill, in cubic metres and litres. A cubic metre is 1,000 litres, and that's how bagged compost and soil are sold. Bags are rounded up, so you never come home one short.
Bulk bags and loose deliveries are often sold by the tonne, so we give a weight range for each material. It is a range because the same soil is much heavier wet than dry, and gravel packs differently by size. Ask your supplier for the weight of their own product if you need it exact. If the area is a lawn, the turf count uses a 1 m² roll unless you change it.
How it is worked out
Area times depth gives the volume. For bags we divide the litres by the bag size and round up. For weight we multiply the cubic metres by a typical weight per cubic metre (bulk density). Our ranges are drawn round published figures: Designing Buildings gives topsoil at 1.31 tonnes per m³, compost at 0.71, bark at 0.26 to 0.36 and pea gravel at 1.6. Quality Garden Supplies puts topsoil at about 1.4 and CalcPros puts mixed gravel at 1.5. One peat-free compost maker gives 0.45 to 0.55 on its data sheet. Turfonline says many UK turf rolls cover 1 m², and suggests about 5% extra for cutting.
Soil and compost settle once watered in, so a new bed often sinks a few centimetres over the first months. Many gardeners buy a little over and top up later.
What to grow in it
Once the bed is full, our vegetable planting calendar shows what to sow and when. Planting out tender crops? Check your average last frost date first.
Garden art prints to go with it
Questions people ask
How much soil do I need for a raised bed?
Length times width times depth, in metres, times 1,000 gives litres. A 2.4 m by 1.2 m bed filled 30 cm deep takes 2.4 × 1.2 × 0.3 × 1,000 = 864 litres, which is 15 bags of 60 litres.
How much does a tonne of gravel cover?
At about 1.5 to 1.7 tonnes per cubic metre, a tonne of gravel is roughly 0.59 to 0.67 m³. Laid 5 cm deep, that covers about 12 to 13 m². Check the figure for the gravel you are buying.
How many litres are in a cubic metre?
Exactly 1,000 litres. So 1 m³ of compost is about 17 bags of 60 litres, or 25 bags of 40 litres.
Should I fill a raised bed with topsoil or compost?
A mix of the two is common. Compost slowly breaks down and sinks, so a bed of mostly compost needs topping up more often. Work out the total volume here, then split it between the two.