Garden Soil Calculator
Figure the soil for a bed of any shape — rectangular, round, or irregular. Enter the dimensions and how deep you're filling, and get the volume in cubic yards and cubic feet plus the number of bags.
The width straight across the round bed.
Estimate the area of an odd shape by splitting it into rectangles and circles, or pacing it out.
Garden soil often comes in 1.5 ft³ bags — confirm on yours.
Advanced: price
Formula & how it works
Rectangle: area = length × width. Circle: area = π × (diameter ÷ 2)². Irregular: enter the area directly.
Volume = area × (depth ÷ 12) cubic feet; cubic yards = ÷ 27; bags = cubic feet ÷ bag volume, rounded up.
Worked example
An 8 × 4 ft bed filled 6 in deep is 32 ft² × 0.5 = 16 ft³, about 0.6 cubic yards — roughly 11 bags at 1.5 ft³. A 6 ft round bed at the same depth is π × 3² × 0.5 ≈ 14 ft³, or about 10 bags.
Filling beds right
Match depth to what you're growing
Shallow-rooted greens and annuals are happy in 6 inches of loose soil, while deep-rooted vegetables, perennials, and shrubs want a foot or more. Topping up an established bed usually needs only a few inches. Because volume scales directly with depth, decide the depth first — it's the biggest lever on how much you buy.
Estimate odd shapes by breaking them up
Curved and irregular beds are easier than they look: split them into rectangles and circles, add the areas, and enter the total in irregular mode. Pacing the outline and sketching it on paper is often accurate enough for ordering soil, where a little extra never hurts.
Soil settles, so round up
Fresh, fluffy soil compacts once it's watered and worked, so the finished level drops below where you filled. Ordering a little more than the bare calculation — and keeping some aside to top off after the first watering — saves a second trip. For planting beds, plan to mix in compost as part of that volume.