Home / Calculators / Raised Bed Soil Calculator
How much soil do I need?
Type your bed’s size — the answer updates as you type. No sign-up, no submit button.
Your bed
How this is calculated
Like a lab worksheet — here is every step, so you can check the working:
- Depth to feet:
depth ÷ 12— e.g. 12 inches = 1 foot. - Cubic feet:
length × width × depth (ft)— e.g. 8 × 4 × 1 = 32 cu ft. - Cubic yards:
cubic feet ÷ 27— there are 27 cubic feet in a cubic yard. - Bags:
cubic feet ÷ 2, rounded up— standard bags hold 2 cu ft. With the settling option on, we add 10% first, because fresh mix compacts after the first waterings. - Mix recipe (60/30/10): 60% topsoil, 30% compost, 10% aeration (perlite or rice hulls) — the widely recommended raised-bed ratio.
- Cost:
cubic feet (with settling) × your price per cu ft. Bagged raised-bed mix typically works out at $4–$6 per cu ft; bulk is often under $2.
What to buy: bags vs bulk
Bags (usually 2 cu ft) win for small jobs — under about 1 cubic yard. They’re easy to carry and you buy exactly what the calculator says, rounded up.
Bulk (sold by the cubic yard, delivered) usually wins at 1 cubic yard and above. A yard of raised-bed mix delivered often costs less than the equivalent bags — but you’ll need somewhere to tip the pile and a wheelbarrow to move it.
Sources & assumptions
Volume math is standard geometry. The 60/30/10 raised-bed mix ratio and depth guidance follow US cooperative extension recommendations (e.g. Cornell, UGA and state extension publications). Bag size assumes the common 2 cu ft bag; “bulk beats bags” around 1 cubic yard is a widely used trade rule of thumb. Prices vary by region — the cost estimate is only as good as the price you enter.
Want the full explanation?
Tables for common bed sizes, how deep your bed should be for different crops, and the 60/30/10 mix in detail.
Soil calculator FAQ
How many bags of soil do I need for a 4×8 raised bed?
A 4×8 ft bed filled 12 inches deep needs 32 cubic feet — that’s 16 two-cubic-foot bags, or 18 with the 10% settling allowance. Shallower beds need proportionally less: at 6 inches deep, it’s 16 cu ft (8 bags).
Should I fill the whole bed with expensive raised-bed mix?
For beds deeper than about 12 inches, many gardeners fill the bottom with cheaper bulk topsoil or logs and branches (hügelkultur style) and put the quality 60/30/10 mix in the top 8–12 inches where the roots are.
What is the 60/30/10 mix?
60% topsoil, 30% compost, 10% aeration (perlite, pumice or rice hulls). It’s the most widely recommended raised-bed recipe from extension sources: structure from the topsoil, nutrients from the compost, drainage from the aeration.
How much does it cost to fill a raised bed?
A standard 4×8×1 ft bed (32 cu ft) costs roughly $130–$190 in bagged mix at typical prices, or $50–$90 in bulk. Enter your local price per cubic foot above for an exact estimate.
Does the soil really settle 10%?
Freshly filled beds commonly settle several inches after the first waterings as air pockets collapse — 10% is a conservative planning allowance. Top the bed back up with compost each season.