Raised bed and planter soil calculator
How much soil to fill raised beds, pots and tree planters, in bags or bulk, and how much soil a tree really needs to grow well.
Filling raised beds and big planters takes more soil than most people expect, and bags add up fast. This works out the volume for beds, round pots and tree planters, and shows how to cut the cost of deep beds.
Tips for filling beds
- A raised bed 4 × 8 ft and 12 in deep holds about 1.2 cubic yards (32 ft³) once settled. That’s over 20 bags of 1.5 ft³.
- Fill in layers and water each one so the soil settles before you plant.
- Top up each spring. Beds sink as organic matter breaks down; an inch or two of compost each year keeps them full.
- Avoid treated wood scraps as filler, and anything painted or glued.
Pots and potting mix
- Potting mix is sold in quarts or cubic feet in the US (8 qt, 16 qt, 1–2 cu ft) and in litres elsewhere. One cubic foot is about 26 quarts or 28 litres.
- Nursery “gallon” sizes are trade sizes, not measurements. A #1 (“1-gallon”) pot holds about 3 quarts; a #5 holds about 4 gallons.
- Use potting mix, not garden soil, in pots. Garden soil packs down in containers and stays waterlogged at the bottom.