Guides / Garden · Updated
How deep should a raised bed be?
From university extension publications (UGA, UC Master Gardeners, Missouri, Illinois, Oregon State, Clemson), checked November 2026.
Short answer
On open ground, 10 to 12 in is enough: UGA says most crops need at least 10 in of soil, and roots keep going into the ground underneath. On a patio or concrete the bed is all the soil there is, so build it 12 in deep for greens and 18 in for tomatoes, potatoes and squash.
Depth by crop
UC Master Gardeners give the soil depth each group of vegetables needs in a container, which is what a raised bed on a hard surface is:
| Crops | Soil depth they need |
|---|---|
| Lettuce, radishes, green onions, spinach, chard, kale, herbs | 9 to 12 in |
| Peas, short carrots, eggplant, peppers | 12 to 14 in |
| Tomatoes, potatoes, zucchini, winter squash, beans, cucumbers | 16 to 18 in |
Source: UC Master Gardeners of Contra Costa County, growing vegetables in containers.
On ground, the bed doesn't have to hold all of that. Loosen the soil inside the frame before filling and the roots go on down. Missouri Extension says most plants need "at least a 6- to 12-inch rooting zone, but deeper would be better," and that beds over 18 to 24 in need to be built like retaining walls, with foundations.
How wide
Wide enough to fill, narrow enough to reach the middle without stepping on the soil:
| Extension service | Reach from both sides | From one side | Paths |
|---|---|---|---|
| UGA | 4 ft adults, 3 ft children | 3 ft from a wheelchair (adults) | 18 to 24 in; 4 ft for carts |
| Missouri | 4 ft | 3 ft | 1 ft on foot; 2 to 3 ft for a wheelbarrow |
| Illinois | 4 ft | 2 ft | — |
| Oregon State (Clackamas) | 4 ft | 2 ft | 14 to 16 in |
| Clemson | 3 to 4 ft | — | 3 to 4 ft between framed beds |
How tall for a wheelchair or a bad back
UGA and Illinois both give 24 in for wheelchair access; Minnesota says 27 in is comfortable for many wheelchair users. Keep a wheelchair bed about 3 ft wide (UGA) and leave 4 ft between beds to turn. UGA adds that a 36 in bed means you don't have to bend over at all.
The raised bed plan builder uses these numbers: tell it what you grow, where the bed sits and who works it, and it picks the boards. The raised bed soil calculator works out the bags to fill it.