How to fill a raised bed
Updated: October 2026
You have the boards in place and a tape in your hand, and the empty rectangle still looks too small to need a sum. How to fill a raised bed is a measured depth, a set of parts, and a litre total, in that order. This page runs a 1.2 m by 0.6 m bed through the Royal Horticultural Society method, so you can see why one bag is not the hole. The [raised bed compost comparison](/hub/raised-beds-greenhouses-and-compost/raised-bed-compost) lines up the six multi-purpose bags. Brand choice stays there.
You have the boards in place and a tape in your hand, and the empty rectangle still looks too small to need a sum. How to fill a raised bed is a measured depth, a set of parts, and a litre total, in that order.
You have the boards in place and a tape in your hand, and the empty rectangle still looks too small to need a sum. How to fill a raised bed is a measured depth, a set of parts, and a litre total, in that order. This page runs a 1.2 m by 0.6 m bed through the Royal Horticultural Society method, so you can see why one bag is not the hole. The raised bed compost comparison lines up the six multi-purpose bags. Brand choice stays there.
Our top picks
| Badge | Product | Beds named | Peat wording | Weight | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Munnie Munnie multi-purpose compost 60 L | – | Enabling the reduction of the use of peat | 14.9 kg | 7.3 | about £9.34 | View offer |
 ecoblaze TerraGrade multipurpose compost 60 L | Raised beds, borders, and garden beds | – | 14.9 kg | 7.3 | about £10.99 | View offer | |
 GROWMOOR Growmoor multi-purpose compost 60 L | Garden beds and borders | – | 14 kg | 7.8 | about £13.98 | View offer |
On this page
How deep the bed should be
Measure the inside first. The RHS treats 30 cm as deep enough for dwarf bulbs, salad, and strawberries. Most other plants, especially fruit bushes, shrubs, and small trees, need 45 cm or more. Finish about 5 cm below the rim, which is the Society's finished level. Ask a landscaper before you fill a bed deeper than 50 cm, or anywhere the weight of wet soil matters.
The parts of the mix
On ordinary ground the mix is seven parts topsoil, three parts organic matter, and two parts horticultural sharp sand. That is 7:3:2, twelve parts in all, so the organic share is three twelfths and the topsoil is the largest share. On paving the sand rises to four parts. The compost versus topsoil page is where you choose the soil itself.
A worked bed of 216 litres
Litres are length times width times depth in metres, times 1,000. A bed of 1.2 m by 0.6 m by 0.30 m is 1.2 × 0.6 × 0.30 × 1,000, which is 216 litres of mix. That figure is the whole fill at 30 cm, not a bag count.
Divide 216 by twelve. Organic matter is 54 litres, topsoil 126 litres, and sharp sand 36 litres, which add back to 216. A 60 litre title is just over that 54 litre share and does not fill 216 litres.
Settle the fill, then plant
Firm the mix as you add it, and stop about 5 cm below the rim. Gardeners' World describes filling to the top and topping up once the compost compacts. Both sources expect about two weeks. Follow the Society for the gap under the rim, and keep the pause either way. A bulk load you cannot barrow is a job for a delivery.
What these bags can and cannot do
The six listings on the main comparison are multi-purpose compost. Count the twin as 60 litres unless the title clearly sells two full bags. None of them replaces 126 litres of topsoil. Do not fill the whole depth with these bags. The raised bed compost buying guide sets those words, and the peat-free compost page covers peat on the bag. There was no laboratory trial.
Common questions
How do I turn metres into litres?
Multiply length, width, and depth in metres, then multiply by 1,000. A bed that is 1.2 m long, 0.6 m wide, and 0.30 m deep is 1.2 × 0.6 × 0.30 × 1,000, which is 216 litres. Use the depth of mix you will put in, not the empty gap under the rim. The result is the whole mix, so split it into parts before you count bags.
What are the RHS parts on soil and on paving?
On ordinary ground the RHS uses seven parts topsoil, three parts organic matter, and two parts horticultural sharp sand. On paving the sand rises to four parts, and topsoil and organic matter stay at seven and three. The organic share is garden compost, leafmould, or well-rotted manure, not bagged potting compost, and the sand is horticultural sharp sand rather than builders' sand. For alpines, bulbs, and herbs that need drainage, double the sand.
How deep should the bed be for salad versus most other plants?
About 30 cm of mix is deep enough for dwarf bulbs, salad, and strawberries. Most other plants, especially fruit bushes, shrubs, and small trees, need 45 cm or more. If you also leave about 5 cm empty below the rim, the boards must be taller than that growing depth. A 30 cm board stopped 5 cm down holds only 25 cm of mix, which is short of the salad figure.
Do I fill a raised bed to the rim?
Stop about 5 cm below the rim and firm the mix. That is the RHS level. Gardeners' World describes filling to the top, then topping up after the compost compacts. Use the Society's gap so the brim is not high from the first day. Expect to add more of the same mix once the surface has sunk, rather than a compost-only cap.
How long do I wait before planting?
Leave the filled bed for about two weeks. That is the pause described by the RHS and by Gardeners' World. Firm the mix, wait, then top up before you plant. If you skip the wait, watering pulls the level down around new plants. A bulk load you cannot move yourself is a delivery job, not another round of bags.
Why does the level drop, and will one 60 litre bag do?
Compost slumps, which is why the RHS wants most of a vegetable bed to be soil. Compaction can also leave a tall brim that shades the plants. In the 216 litre example, three parts in twelve are 54 litres of organic matter. One 60 litre title is just over that share and does not fill the bed. These multi-purpose bags should not be the whole 216 litres.
Related pages
Sources
Public UK sources for the mix, peat wording and sale-of-goods rules. Listing prices and review counts are amazon.co.uk figures from 16 October 2026.
- RHS: How to make a raised bed (retrieved 16 October 2026)
- RHS: Growing veg in raised beds (retrieved 16 October 2026)
- RHS: Peat-free for gardeners (retrieved 16 October 2026)
- GOV.UK: Sale of horticultural peat to be banned (retrieved 16 October 2026)
- Defra written answer, 19 March 2026 (retrieved 16 October 2026)
- BSI PAS 100:2018, specification for composted materials (retrieved 16 October 2026)
- GOV.UK: Use of manufactured topsoil (RPS 190) (retrieved 16 October 2026)
- Consumer Rights Act 2015, section 11 (retrieved 16 October 2026)