Raised Bed Planning: Size It Before You Build It

Pick a width you can reach across

The one rule that matters most: never build a bed wider than twice your comfortable reach. For most people that is about 2 feet from each side, so a 4-foot-wide bed is the sweet spot. You can tend the whole bed without stepping on the soil, which keeps it loose and your plants happy.

If the bed sits against a wall or fence where you can only reach from one side, cap the width at 2 to 2.5 feet.

Length is about your space and your budget

Length is flexible. An 8-foot bed is common because lumber comes in 8-foot lengths, so there is no cutting and no waste. A 4 by 8 bed gives you 32 square feet, enough to feed one or two people a steady supply of greens, herbs, and a few tomatoes.

Want more? Build two 4 by 8 beds with a 2-foot path between them before you build one giant bed. Two beds are easier to reach, rotate, and manage.

Depth depends on what you grow

Most vegetables are happy in 6 to 12 inches of good soil. Match the depth to the deepest roots you plan to grow.

• Leafy greens, herbs, lettuce: 6 inches is plenty.
• Tomatoes, peppers, beans, squash: 10 to 12 inches.
• Carrots and other long roots: at least 12 inches so they do not fork.

Know how much soil you'll need before you buy

Soil is the biggest cost of a new bed, and running short mid-build is the most common mistake. The math is simple: width times length times depth, in feet, gives you cubic feet.

A 4 by 8 bed filled 6 inches deep needs 16 cubic feet, which is eight 2-cubic-foot bags. Use the soil-mix calculator to get the exact amount and a compost, vermiculite, and peat ratio that holds water without going soggy.

Put it where the sun is

Before you commit to a spot, watch it for a day. Most vegetables need 6 to 8 hours of direct sun. Six hours of morning sun beats six hours of harsh afternoon sun, so when in doubt, favor the east side of your yard.