Raised Garden Beds: Size, Material and Soil Guide

Four decisions, in order

Width. Pick a width you can reach across without stepping on the soil. University of Georgia Extension suggests 4 feet for adults who can reach from both sides. If a bed sits against a wall or fence, you only reach from one side, so about 2 feet is a safer limit.
Height. A 12-inch bed suits most vegetables on decent ground. Go taller for comfort or bad soil, not by default, because soil volume rises quickly. See raised bed height for bad knees.
Material. Wood, metal and composite differ mainly in lifespan and upfront cost. Our galvanized vs cedar comparison covers the trade-offs.
Soil. Work this out before you pick a kit, since filling a bed can take more planning than building it. The soil calculator gives you volume, bag count and wet weight.

Volume is length × width × depth. Bag counts use 1.5 cu ft bags, rounded up.
Bed size	Depth	Soil volume	1.5 cu ft bags
2 × 4 ft	12 in	8 cu ft	6
3 × 6 ft	12 in	18 cu ft	12
4 × 4 ft	12 in	16 cu ft	11
4 × 8 ft	12 in	32 cu ft (1.19 cu yd)	22
4 × 8 ft	18 in	48 cu ft (1.78 cu yd)	32
4 × 8 ft	30 in	80 cu ft (2.96 cu yd)	54

Work out the wet weight of a planter and what to ask your building.

Lifespan, heat, safety and assembly compared, with the honest limits of the data.

Which height suits standing, sitting or a wheelchair, and what each one costs in soil.

How wide to go, what to grow in shade, and what must stay clear.

Measure the drop, then dig in, step the sides or terrace.

Once you know your width, height and material, narrow your search to that exact format. See 4 × 8 raised bed kits on Amazon or browse galvanized options.