Planning a raised garden bed? Getting the right amount of soil is one of the most common questions I hear from gardeners. Whether you're using Birdies, Vego, or building your own bed, this free soil calculator helps you figure out exactly how much soil you need — in cubic feet or cubic yards.
Just enter your bed dimensions below, choose your desired depth, and get an exact calculation instantly.
Frequently Asked Questions
A 4×8 foot raised bed at 10 inches deep needs about 26 cubic feet (or roughly 1 cubic yard) of soil. Use our calculator to adjust for your specific depth.
Multiply length × width × depth (in feet), then divide by 27. Our soil calculator does this automatically — just enter your bed dimensions.
A standard 4×4 raised bed at 10 inches deep needs about 13 cubic feet, or roughly half a cubic yard. Depth adjustments change the total — use the calculator for accuracy.
Yes — the custom dimension option works for any brand including Birdies, Vego, Gardeners Supply, and any custom-built bed. Enter your dimensions and desired depth. Even inground beds, as long as you know the Length, Width, and Depth of soil.
Multiply the length by the width by the depth (all in feet). This gives you cubic feet. Divide by 27 to get cubic yards. Our calculator handles all of this automatically.
A 3×6 foot bed at 10 inches deep needs about 15 cubic feet. At 2 cubic feet per bag, that is 8 bags. A 1.5 cubic foot bag would take 10 bags.
Most raised beds work best with 10 to 12 inches of soil. Shallower beds work for shallow-rooted plants like lettuce and herbs. Deeper beds are better for tomatoes, peppers, and root vegetables.
A 40 lb bag of topsoil covers about 0.5 cubic feet at 1 inch deep, or 0.25 cubic feet at 2 inches deep. For a 4×8 bed at 10 inches, you would need about 52 bags.
Avoid filling with only compost (it settles too fast), treated wood chips, dirt from treated areas, or materials that compact. Stick with a mix of topsoil, compost, and aeration materials.
Two inches is a good top dressing for existing beds, but it is not enough to grow in. For new beds, you need at least 8 to 12 inches of good soil for vegetables to thrive.
Cubic feet = length (ft) x width (ft) x depth (ft). Cubic yards = cubic feet ÷ 27. Our calculator does the math for you.
Buy soil in bulk from a local landscape supplier. A cubic yard costs less than buying individual bags. Some suppliers deliver, which saves you hauling dozens of bags. If you prefer a well made soil with great nutrients, in the Northeast Florida area I recommend Man in Overalls. They deliver and they'll even wheelbarrow and load your beds, too.
No. Rocks actually drainage and create a water table where roots cannot reach. Fill your bed with good soil from the start. If drainage is a problem, mix in perlite or coarse sand.
Bulk is usually cheaper. One cubic yard of topsoil costs roughly what 18 to 20 bags would cost. If you need more than 20 bags, bulk delivery saves money.
Most 40 lb bags of potting soil are about 1 cubic foot. Check the label — some brands vary. This is why our calculator asks for your bag size.
Measure your bed length, width, and desired depth in feet. Multiply those three numbers. Divide by 27 for cubic yards. Enter it all into our calculator.
The 70/30 rule suggests 70% topsoil and 30% compost for raised beds. This gives good structure and drainage plus nutrients. Some gardeners go 50/50, especially in Florida sand. In the deeper garden beds (taller than 2 feet) I like to include a lot of perlite to help reduce compaction.
Yes, tomatoes can grow in 10 inches, but they will be more productive with 12 to 18 inches. Use a deep planter or tall raised bed for the best harvest.
First calculate total cubic feet you need. Divide by the cubic feet per bag (usually 1 or 2 cubic feet). Round up. Our calculator shows both total cubic feet and bag counts.
Topsoil is usually cheaper per cubic foot. Compost costs more but you only need 25 to 30% of your mix. For filling a new bed, buy mostly bulk topsoil and add compost.
Fall is ideal — add it before winter rains help it settle. Spring works too, but add it a few weeks before planting so it has time to settle and warm up.
Soil Calculator for Pots and Containers
Growing in pots? The calculation is different. Multiply the diameter (in feet) by itself, then multiply by the depth you need. This gives you cubic feet. A 5-gallon pot is roughly 0.7 cubic feet. Use our calculator to figure out exactly what you need for containers of any size, round, square, or rectangular.
Understanding Cubic Yards
A cubic yard is 27 cubic feet. Most soil suppliers sell by the cubic yard, so it is the most useful measurement for bulk orders. Our calculator shows both cubic feet and cubic yards so you can order with confidence.
If your calculation shows you need 10 cubic feet, that is roughly 0.37 cubic yards. Most suppliers have a 1-yard minimum for delivery.
Bulk vs Bagged Soil: Which is Cheaper?
Bulk soil costs less per cubic foot. One cubic yard of topsoil costs roughly $30 to $50 plus delivery, while buying that same amount in bags would cost $100 or more. The trade-off is bulk requires a truck or delivery, while bags are easier to transport yourself.
When to choose bulk: You need more than 10 bags, you have a way to transport it, or you want to save money.
When to choose bags: You only need a small amount, you cannot transport bulk, or you need it immediately.
How Many Bags of Soil Do You Need?
Most bags come in 1 cubic foot or 2 cubic foot sizes. Here is a quick reference:
- 4×4 raised bed at 10 inches deep = 13 cubic feet = 13 bags (1 cu ft) or 7 bags (2 cu ft)
- 4×8 raised bed at 10 inches deep = 26 cubic feet = 26 bags (1 cu ft) or 13 bags (2 cu ft)
- 3×6 raised bed at 10 inches deep = 15 cubic feet = 15 bags (1 cu ft) or 8 bags (2 cu ft)
Mulch and Soil Calculator
Mulch is sold by the cubic yard too, but you need a thinner layer. For 2 inches of mulch over a 4×8 bed, you need about 4 cubic feet. Use our calculator to figure out both soil and mulch in one place.
Top Soil Calculator by Bed Size
Here are the most common bed sizes and how much soil they need at 10 inches deep:
- 2×2 = 3.3 cubic feet
- 2×4 = 6.7 cubic feet
- 3×3 = 7.5 cubic feet
- 3×6 = 15 cubic feet
- 4×4 = 13.3 cubic feet
- 4×8 = 26.7 cubic feet
- 4×12 = 40 cubic feet