Raised Bed Soil Calculator | How Much Soil and How Many Bags You Need
Enter the length, width and fill depth of your raised bed and get the soil volume in cubic feet and cubic yards (or liters and m³ in metric), plus how many bags to buy, rounded up. Plan the trip to the garden center before you load the cart.
💡 About this tool
The math behind filling a raised bed is just length × width × depth, but it rarely feels that simple at the store. Your bed is in feet, the depth is in inches, and the bags are labeled in cubic feet — so the mental conversion is where people guess wrong, buy four bags too few, and make a second trip. This calculator does the unit juggling for you and then divides by your bag size, rounding up so you never come up short.
Type in an 8 ft × 4 ft bed filled 12 in deep and you get 32 cu ft (about 1.19 cu yd); at a common 1.5 cu ft bag that's 22 bags. The depth field carries a "6–12 in" reminder and the bag field an "e.g. 1–2 cu ft" hint, so even a first-time bed builder lands on realistic inputs. English-speaking gardeners can flip the unit toggle to centimeters and liters if they prefer metric.
🧐 Frequently Asked Questions
How deep should I fill the bed? It depends on the crop. Lettuce, herbs and other shallow-rooted greens are happy in about 6 in, while tomatoes, peppers and root vegetables do better with 10–12 in or more. If you're not sure, estimate on the deeper side (the tool defaults to 12 in) so the same bed works when you rotate to a hungrier crop next season.
Will the exact bag count be enough? The bag count is rounded up from the geometric volume, so it meets the math — but fresh soil settles and compacts after watering and planting. The surface usually drops, so as the results note suggests, buying roughly 10–20% extra spares you a return trip to top it off.
My bed needs a huge number of bags — is that normal? For larger beds the bag count climbs fast. Once you're past about one cubic yard, bulk soil delivered loose is often cheaper per volume and easier to handle than stacks of bags. Because this tool reports the total in cu ft / cu yd first, you can see at a glance whether bagged or bulk makes more sense.
Can I switch between US and metric units? Yes. The unit toggle (English version) swaps between feet/inches with cubic-feet output and centimeters with liter output, so you can match whatever your bags and tape measure use.
📚 Why raised beds change the soil math
A raised bed isn't just a box of dirt — it's a defined volume you fill once and top up over time, which is exactly why a volume estimate matters more here than in an open garden plot. Unlike in-ground beds, you can't borrow soil from the surrounding earth, so under-buying is felt immediately as a half-empty frame.
One quirk worth knowing: soil bags list both a volume and a weight, and the two don't track each other. A dense topsoil and an airy potting mix can share the same cubic-foot label while weighing very differently, so plan your calculation around volume (what this tool returns) and check the per-bag weight separately if you're carrying them up stairs or into a backyard.