Introduction
Building a raised bed garden is exciting, but figuring out how much soil you need can be tricky. Our Raised Bed Soil Calculator works out how much soil your bed needs. Just enter the length, width, and depth of your raised bed, and the tool will tell you exactly how much soil to buy. This saves you time, money, and extra trips to the garden center. This calculator helps you get the right amount of soil every time, for a single bed or a whole garden. No more buying too much or too little, just the perfect fill for healthy plants and strong roots.
How to Use Our Raised Bed Soil Calculator
Enter the size of your raised bed below, and this calculator will tell you exactly how much soil you need to fill it.
Unit system: Choose Imperial (feet and inches) or Metric (centimeters).
Soil mix: Set the percentages of topsoil, compost, and perlite or vermiculite. They must add up to 100%, and the breakdown table splits each bed's volume by them.
Bed shape: Each bed can be a rectangle, a circle, or an L-shape (an outer rectangle with a cutout rectangle taken away). Use Add Another Bed to include more beds in the total.
Length: Enter the length of your raised bed. Measure from one end to the other along the longest side.
Width: Enter the width of your raised bed. This is the shorter side of your bed.
Depth: Enter how deep the soil will be, in inches or centimeters. The Quick Fill by Plant menu can fill in a depth for the crops you plan to grow.
Results: The calculator shows the total soil volume, the number of 1- and 2-cubic-foot bags (28- and 57-liter bags in metric), and cubic yards. Bulk soil is usually sold by the cubic yard, so this number helps you know how much to order.
Raised Bed Soil Calculator
A raised bed is a garden built on top of the ground, usually held in place by a frame made of wood, stone, or metal. Raised beds are popular because they give you better control over your soil, drain water more easily, and keep weeds out. They also warm up faster in spring, which means you can start planting sooner.
How Much Soil Do You Need?
Figuring out the right amount of soil for your raised bed is one of the most important steps before planting. If you add too little soil, your plants won't have enough room for their roots to grow. Too much soil can be a waste of money. This calculator helps you find the exact volume of soil you need based on the size of your raised bed.
Understanding Soil Volume
Soil volume is measured in cubic feet or cubic yards. To find the volume, you multiply the length, width, and depth of your raised bed together. With all three in inches, divide by 1,728 to get cubic feet, because a cubic foot is 1,728 cubic inches.4 A cubic yard is 27 cubic feet.4 A soil-and-organic mix about 8 inches deep is enough for the roots of most vegetable plants.2 On a hard surface such as a driveway, a bed should be at least 8 inches deep for leafy greens, beans, and cucumbers, and 12 to 24 inches deep for peppers, tomatoes, and squash.1
What Kind of Soil Should You Use?
The best soil mix for raised beds is a blend of three things:
- Topsoil – makes up the bulk of your bed and gives structure
- Compost – adds nutrients that feed your plants
- Perlite or coarse sand – helps with drainage so roots don't sit in water
A good fill is compost and topsoil mixed in a 1:2 or 1:1 ratio, or compost and a soilless growing mix in a 1:1 ratio.1 In a bed that contains garden soil, organic matter should make up 25% to 50% of the volume.1 Do not fill a raised bed with compost alone, because compost lacks the mineral part of soil that plants need.3 You may also want to add a layer of pea gravel at the bottom of deeper beds to improve drainage further.
Helpful Tips
Keep in mind that soil settles over time. Expect a newly filled bed to sink as the compost in the mix breaks down, and refill it as needed.3 It's a good idea to buy a little extra soil so you can top it off later. Also, adding a fresh layer of compost each season keeps the soil healthy and full of nutrients for your next round of plants.