Introduction
Figuring out how much soil you need for a garden bed, raised planter, or landscaping project can be tricky. Buy too little and you'll make extra trips to the store. Buy too much and you'll waste money and have piles of leftover dirt. This Soil Calculator tells you the exact volume of soil you need based on your project's dimensions.
Simply enter the shape and size of your planting area (a rectangle, circle, triangle, or an irregular shape) along with the desired depth. The calculator instantly gives you results in cubic feet, cubic yards, and liters. It also estimates the total weight based on your soil type (potting mix, garden soil, or topsoil) and tells you how many bags to buy at common store sizes, with a built-in 10% waste factor so you don't come up short.
Need to plan for multiple garden beds at once? Use the multi-zone feature to add separate areas with different shapes and depths, and the calculator will add everything up for you. You can also use the quick depth presets, from 6 inches for flowers to 24 inches for shrubs, based on standard planting guidelines. This tool helps you get the right amount of soil the first time, for a small container or an entire backyard garden.
How to use our Soil Calculator
Enter the dimensions of your garden bed or planting area, and this calculator will tell you exactly how much soil you need in cubic feet, cubic yards, liters, and bags.
Calculator Mode: Choose between "Dimensions Mode" to enter the length, width, and depth of your space, or "Area Mode" if you already know the total square footage of your planting area.
Soil Type: Select the type of soil you plan to use: Potting Mix, Garden Soil, or Topsoil. Each type has a different weight per cubic foot, which affects the weight estimate and bag count.
Shape (Dimensions Mode): Pick the shape that best matches your garden bed: Rectangle, Circle, Triangle, or Irregular. The calculator will show a diagram and ask for the right measurements based on the shape you choose.
Length and Width (Rectangle): Enter the length and width of your rectangular bed, and choose the unit (feet, inches, yards, meters, or centimeters) from the dropdown next to each field.
Diameter (Circle): If your bed is round, enter the full diameter (the distance across the widest part of the circle) and pick your unit.
Base and Height (Triangle): For a triangular bed, enter the base length and the height from the base to the opposite point, along with their units.
Area (Irregular Shape): If your bed has an odd shape, enter the total area in square feet, square yards, or square meters directly.
Depth: Enter how deep you want the soil to be. You can type in a number and pick a unit, or click a quick preset like 6 inches for flowers, 12 inches for vegetables, or 24 inches for shrubs.
Total Area (Area Mode): If you already know the square footage of your space, enter it here and select the unit: square feet, square yards, or square meters.
Add Another Zone: If you have more than one garden bed, click "Add Another Zone" to enter dimensions for each area separately. The calculator will add them all together and show a zone-by-zone breakdown in the results.
Calculate: Press the "Calculate" button to see your total soil volume, estimated weight, bag recommendations (with a 10% waste factor built in), and a full volume conversion table covering cubic feet, cubic yards, cubic meters, liters, gallons, and quarts.
Soil Calculator: How Much Soil Do You Need?
Figuring out how much soil to buy for a garden bed, raised bed, or planting area can be tricky. If you buy too little, you'll need extra trips to the store. If you buy too much, you waste money and end up with piles of unused dirt. This soil calculator helps you find the exact amount of soil you need based on the size and shape of your planting area.
How Soil Volume Is Calculated
The amount of soil you need depends on three things: the length, width (or diameter), and depth of the area you want to fill. The calculator multiplies these measurements together to get a volume, usually shown in cubic feet or cubic yards. For a rectangular bed, the formula is simple: length × width × depth. For circular areas, it uses the diameter to find the area of the circle first, then multiplies by depth. Triangular and irregular shapes each have their own formulas built in.
Why Soil Depth Matters
Different plants need different amounts of soil to grow healthy roots. Here are some common guidelines:
- 6 inches: Good for flowers and shallow-rooted annuals
- 8 inches: Works well for leafy greens like lettuce and spinach
- 12 inches: The standard depth for most vegetables like tomatoes, peppers, and beans
- 18 inches: Needed for deep-rooted crops like carrots, potatoes, and parsnips
- 24 inches: Best for shrubs, berry bushes, and small trees
Choosing the right depth helps your plants develop strong root systems, which leads to better growth and bigger harvests.
Understanding Soil Types and Weight
Not all soil weighs the same. Potting mix is lightweight, typically around 25 pounds per cubic foot, because it contains perlite, peat moss, and other airy materials. Garden soil and topsoil are much heavier, weighing about 75 pounds per cubic foot, since they contain more minerals, clay, and moisture. Knowing the weight matters when you're hauling bags in your car or planning a bulk delivery by the truckload.
Buying Bags vs. Bulk Soil
Bagged soil comes in standard sizes like 0.75, 1.0, 1.5, 2.0, and 3.0 cubic feet. For small projects like a single raised bed, bags are convenient. For larger jobs, buying soil in bulk by the cubic yard is usually cheaper. One cubic yard equals 27 cubic feet, which is enough to fill a 4×8-foot raised bed about 10 inches deep.
The calculator adds a 10% waste factor to its bag estimates. This accounts for soil that spills, settles after watering, or gets left behind in bags. Soil naturally compacts over time, so having a little extra on hand is always a smart idea.
Tips for Filling Raised Beds and Garden Areas
- Mix soil types: A blend of topsoil, compost, and potting mix creates a rich growing medium with good drainage.
- Expect settling: Fresh soil can settle by 10 to 20% after the first few waterings. Top off beds as needed.
- Use the zone feature: If your garden has beds of different shapes and sizes, add multiple zones to get one combined total instead of calculating each bed separately.
- Test your soil: Before adding new soil, consider a soil test to check pH and nutrient levels. This helps you pick the right amendments and the right amount of fertilizer from the start.
- Plan complementary materials: Many garden projects also call for mulch, pea gravel for drainage layers, or sand for soil amendment.
Knowing your exact soil needs saves time, money, and effort on a new raised bed, containers on a patio, or a large garden plot. Enter your measurements above to get started.