Raised Bed Soil Calculator
Find out how much soil your raised garden bed needs. Enter length, width and depth to get cubic feet, cubic yards and the number of 1.5 cu ft bags to buy.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the Raised Bed Soil Calculator Works
This calculator tells you how much soil to buy to fill a rectangular raised garden bed. Enter the bed’s length, width and soil depth in feet, and it returns the volume three ways: in cubic feet, in cubic yards for bulk orders, and as the number of 1.5 cubic foot bags to buy.
Because the result is given in both bags and cubic yards, you can decide whether bagged soil or a bulk delivery is the better value for your project.
The Formula
A raised bed is a simple box, so its volume is length times width times height:
Volume (ft³) = length × width × soil depth (all in feet) Cubic yards = Volume (ft³) ÷ 27 Bags = ceil(Volume (ft³) ÷ 1.5)
There are 27 cubic feet in a cubic yard (3 × 3 × 3 ft). Standard bagged garden soil comes in 1.5 cubic foot bags, and the bag count is rounded up so you always have enough.
Worked Example
For an 8 ft long, 4 ft wide bed filled 1 ft deep:
- Volume = 8 × 4 × 1 = 32 ft³
- Cubic yards = 32 ÷ 27 = ≈ 1.19 yd³
- Bags = ceil(32 ÷ 1.5) = ceil(21.3) = 22 bags
If you only fill the bed to 10 in (0.83 ft) deep instead:
- Volume = 8 × 4 × 0.83 = ≈ 26.6 ft³
- Bags = ceil(26.6 ÷ 1.5) = 18 bags
A 2-inch reduction in depth saves four bags of soil.
Bagged vs. Bulk Soil
| Volume needed | Best buying option |
|---|---|
| Under 0.5 yd³ (≈ 13.5 ft³) | Bags — easy to handle, no delivery fee |
| 0.5 – 1 yd³ | Either — compare price per cubic foot |
| Over 1 yd³ (≈ 27 ft³) | Bulk delivery — cheaper per yard |
A single cubic yard is roughly 18 standard 1.5 cu ft bags, so once you pass about one cubic yard, bulk soil usually wins on price and effort.
Tips for Filling a Raised Bed
- Measure inside dimensions. Use the interior length and width, not the outside of the frame boards.
- Use soil depth, not frame height. If you leave a few inches of freeboard at the top, only count the depth you actually fill.
- Mix a soil blend. A common recipe is about 60 percent topsoil, 30 percent compost and 10 percent aeration like perlite — calculate the total, then split by ratio.
- Expect settling. Fresh soil compacts over the first season, so top up with an extra bag or two after the first few weeks.
Getting the volume right means one trip to the garden center or one bulk delivery, instead of repeated runs for “just a couple more bags.”
Frequently asked questions
How much soil do I need for a raised bed?+
Multiply the bed's length × width × depth in feet to get cubic feet of soil. For an 8 ft × 4 ft bed filled 1 ft deep, that is 8 × 4 × 1 = 32 cubic feet, which is about 1.19 cubic yards or 22 standard 1.5 cu ft bags.
How do I convert cubic feet of soil to cubic yards?+
Divide the cubic feet by 27, because one cubic yard equals 27 cubic feet (3 ft × 3 ft × 3 ft). So 32 cubic feet ÷ 27 = about 1.19 cubic yards. Bulk soil is usually sold by the cubic yard, so this conversion helps when ordering in bulk.
How many bags of soil for a raised bed?+
Divide the cubic feet by the bag size and round up. Most bagged soil is sold in 1.5 cubic foot bags, so a 32 cubic foot bed needs ceil(32 ÷ 1.5) = 22 bags. The calculator rounds up so you never come up short.
What depth of soil does a raised bed need?+
Most vegetables need 10–12 inches (about 0.83–1 ft) of soil for healthy roots. Shallow-rooted greens manage with 6 inches, while deep-rooted crops like carrots and tomatoes prefer 12–18 inches. Use the soil depth, not the full height of the frame.
Should I fill the entire raised bed with soil?+
Not always. For deep beds you can fill the bottom third with logs, branches or coarse compost (a method called hugelkultur) to save soil and improve drainage. In that case, only enter the actual depth of soil you plan to add, not the full frame height.