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Garden Bed Soil Calculator
Any bed size, any depth — soil volume, cubic yards, and bag count, instantly.
REFERENCE TABLE · EVERYDAY · GARDEN
Garden Bed Size Chart — Soil Volume & Planting Guide
The classic 4×8 ft bed holds 32 cu ft (1.19 cu yd) of soil at 12 inches deep — 16 bags of 2-cu-ft mix over 32 sq ft of planting area. Below: seven standard beds with their soil volumes and bag counts, plus a live calculator for any length, width, and depth. (This is a size and soil-volume chart, not a planting calendar or spacing guide.)
The standard bed sizes — soil at 12 inches deep
Seven beds that cover nearly every backyard, with the soil each one holds at the standard 12-inch depth. Soil in cubic feet is length × width × depth÷12; cubic yards are cubic feet ÷ 27; bags assume standard 2-cu-ft bags:
| Bed (L×W ft) | Area (sq ft) | Soil (cu ft) | Soil (cu yd) | 2-cu-ft bags | What to grow |
|---|---|---|---|---|---|
| 2×4 | 8 | 8 | 0.30 | 4 | herbs & salad greens |
| 3×6 | 18 | 18 | 0.67 | 9 | peppers, eggplant & a tomato or two |
| 4×4 | 16 | 16 | 0.59 | 8 | a square-foot salad garden |
| 4×8 | 32 | 32 | 1.19 | 16 | the classic all-purpose bed |
| 4×10 | 40 | 40 | 1.48 | 20 | tomatoes, peppers & herbs together |
| 4×12 | 48 | 48 | 1.78 | 24 | a serious vegetable rotation |
| 6×12 | 72 | 72 | 2.67 | 36 | a family-size kitchen garden |
The default bed is 4×8 ft: 32 sq ft of planting area, 32.00 cu ft of soil, 1.19 cu yd, 16 bags. It is the classic for a reason — 4 feet is the widest bed you can reach across from either side without stepping in it, and 8 feet is the length of a standard board, so nothing gets cut.
How the math works
Soil in cubic feet = length × width × depth÷12. A 4×8 bed at 12 inches deep is 4 × 8 × 1 = 32 cu ft. Cubic yards = cubic feet ÷ 27 (there are 27 cubic feet in a cubic yard): 32 ÷ 27 = 1.19 cu yd — the number bulk suppliers quote. Bags = cubic feet ÷ 2, rounded up: 32 ÷ 2 = 16 bags of 2-cu-ft mix. Halve the depth to 6 inches and everything halves: the same 4×8 bed takes 16 cu ft, 0.59 cu yd, 8 bags. The reverse question is just as useful: a 4×8 bed gives 32 sq ft of planting area, while a 4×4 gives 16 sq ft — so two 4×4 beds equal one 4×8, with a path between them.
Depth, reach, and what not to fill with
12 inches suits nearly everything — tomatoes, peppers, carrots, and herbs all root happily in it. 6 inches is fine for lettuce, herbs, and radishes, and it halves your soil bill. 18 inches is for deep-rooted crops and gardeners who want to garden standing up, but it costs 50% more soil than the standard. Keep beds no wider than 4 feet so you can reach the middle from either side; longer than 12 feet, add a cross-brace or the sides bow. And do not fill the whole bed with bagged topsoil: a cheap bottom layer of logs, branches, and leaves (the hugelkultur trick) rots down into soil over a season and can cut the bag count by a third.
What this page is not: this is a size and soil-volume chart, not a planting calendar or a spacing guide. It will not tell you when to sow or how far apart to space seedlings — only how big to build and how much soil to buy.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Planting area | length × width | 32 sq ft at the defaults — how much you can actually grow in. |
| Soil (cubic feet) | length × width × depth÷12 | 32.00 cu ft at the defaults — the bag-math number. |
| Soil (cubic yards) | cubic feet ÷ 27 | 1.19 cu yd at the defaults — the bulk-order number. |
| Bags (2 cu ft) | ceil(cubic feet ÷ 2) | 16 bags at the defaults — the shopping-list number. |
Who uses this
- First-time vegetable gardeners: the 4×8 row is the starter bed — 16 bags and one Saturday afternoon.
- Bulk-soil buyers: cubic yards are what the yard quotes — 1.19 cu yd for the classic bed, 2.67 for the big 6×12.
- Square-foot gardeners: the area column doubles as your planting grid — 32 squares in the 4×8.
- Teachers & community gardens: the 2×4 and 4×4 rows are the kid-sized beds — cite the chart with the block below.
Accuracy & limitations
Volumes assume a rectangular bed filled level to the top — soil settles 10–20% in the first weeks, so buy a bag or two extra, or top up after the first rain. Bag sizes vary (1.5-cu-ft and 3-cu-ft bags exist) — divide by your bag's size, not by 2, if yours differ. Cubic-yard figures are rounded to two decimals; order a little over, never under. Planting suggestions are general guidance, not a growing calendar.
Cite this reference tableBright Side Kit. “Garden Bed Size Chart — Soil Volume & Planting Guide.” brightoolbox.com, 2026.
Bright Side Kit. "Garden Bed Size Chart — Soil Volume & Planting Guide.." https://brightoolbox.com/garden-bed-size-chart/ Accessed October 23, 2026.Frequently asked questions
How much soil do I need for a 4×8 raised bed?
At the standard 12-inch depth: 32 cu ft (1.19 cu yd), or 16 bags of 2-cu-ft mix. The formula is length × width × depth÷12 = 4 × 8 × 1 = 32 cu ft. Buy 17 or 18 bags — soil settles 10–20% in the first weeks.
How many bags of soil for a 4×4 raised bed?
8 bags of 2-cu-ft mix at 12 inches deep (16 cu ft, 0.59 cu yd). A 4×4 is exactly half the classic 4×8, so it takes exactly half the soil — and gives exactly half the planting area, 16 sq ft.
How deep should a raised garden bed be?
12 inches suits nearly everything — tomatoes, peppers, carrots, and herbs. 6 inches is enough for lettuce, herbs, and radishes and halves your soil bill (a 4×8 takes 16 cu ft instead of 32). 18 inches is for deep-rooted crops and standing-height gardening.
How do I convert cubic feet of soil to cubic yards?
Divide by 27 — there are 27 cubic feet in a cubic yard. 32 cu ft ÷ 27 = 1.19 cu yd for the classic 4×8 bed. Bulk suppliers quote in yards; bags are sold in cubic feet.
How much soil for a 6×12 raised bed?
72 cu ft, 2.67 cu yd, or 36 bags of 2-cu-ft mix at 12 inches deep, over 72 sq ft of planting area. At this size, bulk delivery in cubic yards is usually cheaper than bags — order 2.75 cu yd to cover settling.
What if my bed is only 6 inches deep?
Everything halves: a 4×8 bed at 6 inches takes 16 cu ft, 0.59 cu yd, 8 bags instead of 32 cu ft and 16 bags. Shallow beds suit salads and herbs, but tomatoes and carrots want the full 12 inches.
Should I fill the whole bed with bagged topsoil?
No — it is the expensive way. Fill the bottom third with logs, branches, and leaves: they rot down into soil over a season and can cut the bag count by a third. Top the last 8–12 inches with quality garden soil or a soil-and-compost mix — that is the layer the roots actually live in.
Is this a planting calendar or a spacing guide?
No. This page covers only bed sizes and soil volume — how big to build and how much soil to buy. It does not say when to sow or how far apart to space seedlings; your seed packets and local frost dates answer those.