Garden Bed Calculator
A garden bed calculator finds the soil and lumber for a raised bed. Enter the inside length, width and soil depth to read cubic feet, cubic yards, bags and a mix split. A 4 by 8 foot bed filled 10 inches deep needs 26.67 cubic feet before settling.
This tool is part of our volume calculators. Use it to size an order and a frame. Check the bag label and your supplier's bulk density before you buy.
- Updated October 2026
- Sources Cited
- No Login Required
- Free to Use
Your garden bed
Soil to buy
1.09 cu yd
29.33 cu ft, or 20 bags of 1.5 cu ft
- Soil before settling
- 26.67 cu ft
- Cubic meters
- 0.831
- Weight
- 1,630 lb (0.81 tons)
- Bed height
- 11.25 in
Across the cited depth range: 29.33 to 35.2 cu ft, or 1.09 to 1.3 cu yd (20 to 24 bags).
Soil mix split
- Topsoil17.6 cu ft (12 bags)
- Compost8.8 cu ft (6 bags)
- Aeration (coir, perlite or potting mix)2.93 cu ft (2 bags)
Lumber list
- Long boards2 at 99 in (8 ft 3 in)
- Short boards2 at 48 in (4 ft 0 in)
- Total length24.5 linear ft
- 2x12 boards to buy3 at 12 ft
Long boards run the full outside length. Short boards fit between them. Saw cuts are not counted.
Weight uses your bulk density. Wet soil weighs more.
Depth by crop
Low and high soil quantity from cited depth ranges.
Mix split
Three recipes split your total into parts.
Lumber list
Cut list and stock boards from actual board sizes.
Estimates are for material planning. Soil depth advice differs by crop and local conditions. Check your supplier's product sheet.
How to calculate soil for a garden bed
Multiply the inside length in feet by the inside width in feet. Multiply by the soil depth in inches, then divide by 12 to get cubic feet. Divide by 27 for cubic yards. A 4 by 8 foot bed at 10 inches deep holds 26.67 cubic feet, or 0.99 cubic yards.
- Measure the inside of the bed, not the outside of the boards.
- Pick the soil depth for your crop from the table below.
- Cubic feet equal length times width times depth in inches, divided by 12.
- Cubic yards equal cubic feet divided by 27.
- Add a settling allowance, then divide by the bag size and round up for bags.
To find the area of an odd space first, use our square footage calculator. To add the volumes of several materials for one delivery, use the cubic yards calculator.
How deep should raised bed soil be?
Eartheasy lists 6 to 8 inches for herbs and greens, 10 to 12 inches for most vegetables and 18 to 24 inches for deep-rooted crops. UF/IFAS advises 6 to 8 inches of soil in a bed. Soil depth is the fill depth, not the height of the boards.
| What you grow or do | Soil depth | Source |
|---|---|---|
| Refresh or top-dress an existing bed | 2 to 4 in of new mix | Eartheasy |
| Herbs, lettuce and other shallow-rooted greens | 6 to 8 in | Eartheasy |
| Most vegetables (tomatoes, peppers, beans, squash) | 10 to 12 in | Eartheasy |
| Deep-rooted crops (carrots, parsnips, potatoes) | 18 to 24 in | Eartheasy |
| A raised bed in general | 6 to 8 in of soil | UF/IFAS Extension, St. Lucie County, February 2025 |
Worked example: a 4 by 8 foot raised bed
A 4 by 8 foot bed has 32 square feet. At 10 inches deep, that is 26.67 cubic feet. With 10 percent settling, you buy 29.33 cubic feet, or 1.086 cubic yards. In bags of 1.5 cubic feet, the bed needs 20. The University of Georgia Extension works the same bed at 10 inches and gets 26.66 cubic feet.
| Bed and depth | Cubic ft | Cubic yd | With 10% settling, cu ft | Bags of 1.5 cu ft | Bags of 2 cu ft |
|---|---|---|---|---|---|
| 4 x 8 ft at 10 in | 26.67 | 0.988 | 29.33 | 20 | 15 |
| 4 x 8 ft at 6 in | 16.00 | 0.593 | 17.60 | 12 | 9 |
| 4 x 8 ft at 12 in | 32.00 | 1.185 | 35.20 | 24 | 18 |
| 4 x 4 ft at 10 in | 13.33 | 0.494 | 14.67 | 10 | 8 |
| 3 x 6 ft at 10 in | 15.00 | 0.556 | 16.50 | 11 | 9 |
Soil needed by garden bed size
A 4 by 8 foot bed needs 16 cubic feet at 6 inches and 32 cubic feet at 12 inches, which is 1.19 cubic yards. The table lists six common bed sizes before settling, with bag counts for 1.5 cubic foot bags at 12 inches.
| Bed size | Soil at 6 in, cu ft | Soil at 12 in, cu ft | 12 in, cu yd | Bags of 1.5 cu ft, 12 in |
|---|---|---|---|---|
| 2 x 4 ft | 4.00 | 8.00 | 0.30 | 6 |
| 4 x 4 ft | 8.00 | 16.00 | 0.59 | 11 |
| 3 x 6 ft | 9.00 | 18.00 | 0.67 | 12 |
| 3 x 8 ft | 12.00 | 24.00 | 0.89 | 16 |
| 4 x 8 ft | 16.00 | 32.00 | 1.19 | 22 |
| 4 x 12 ft | 24.00 | 48.00 | 1.78 | 32 |
UF/IFAS Extension gives 3 to 4 feet as the width of a raised bed. Length can be any size. For soil laid in a lawn or in-ground bed, use the topsoil calculator.
Raised bed soil mix recipes
Eartheasy gives three common blends. One is 50 percent soil, 30 percent compost and 20 percent potting mix. Another is 60 percent topsoil, 30 percent compost and 10 percent aeration. Mel's Mix uses equal parts compost, peat or coir, and coarse vermiculite. The calculator splits your total volume for the recipe you pick.
| Recipe | Parts | Cubic ft of each part for 29.33 cu ft |
|---|---|---|
| 60 topsoil, 30 compost, 10 aeration | Topsoil, Compost, Aeration (coir, perlite or potting mix) | 17.60 / 8.80 / 2.93 |
| 50 soil, 30 compost, 20 potting mix | Soil, Compost, Potting mix | 14.67 / 8.80 / 5.87 |
| Mel's Mix: equal thirds | Compost, Peat moss or coir, Coarse vermiculite | 9.78 / 9.78 / 9.78 |
For the compost part, size an order with the compost calculator. Eartheasy warns that bagged topsoil or native dirt alone compacts and drains poorly in a raised bed, so use it as part of a blend.
How much lumber does a raised bed need?
A nominal 2x12 measures 1.5 by 11.25 inches, so one course makes a bed 11.25 inches tall. A 4 by 8 foot bed with inside sizes needs two 99 inch boards and two 48 inch boards, which is 24.5 linear feet. Three 12 foot boards cover those cuts.
| Nominal board | Actual size, in | Bed height, 1 course, in | Bed height, 2 courses, in |
|---|---|---|---|
| 2x6 | 1.5 x 5.5 | 5.5 | 11 |
| 2x8 | 1.5 x 7.25 | 7.25 | 14.5 |
| 2x10 | 1.5 x 9.25 | 9.25 | 18.5 |
| 2x12 | 1.5 x 11.25 | 11.25 | 22.5 |
Actual sizes follow the American Softwood Lumber Standard PS 20-20, as listed by SPIB. The cut list does not count saw cuts. UF/IFAS Extension lists untreated lumber, concrete blocks and landscaping ties as bed borders. This page does not advise on wood treatment.
How many bags of soil do I need?
Divide cubic feet by the bag size and round up. A 4 by 8 foot bed at 10 inches deep with 10 percent settling needs 29.33 cubic feet. That is 20 bags of 1.5 cubic feet or 15 bags of 2 cubic feet. Check the volume printed on the bag.
| Bag size | Bags per cubic yard | Bags for the example bed |
|---|---|---|
| 0.75 cu ft | 36 | 40 |
| 1 cu ft | 27 | 30 |
| 1.5 cu ft | 18 | 20 |
| 2 cu ft | 13.5 | 15 |
| 3 cu ft | 9 | 10 |
Bags are sold by volume, and weights vary. For other bagged materials, use the cubic feet calculator.
How much does raised bed soil weigh?
Eartheasy lists screened topsoil at 2,000 to 2,200 pounds per cubic yard and compost at 1,000 to 1,400. A 50/30/20 blend runs 1,300 to 1,700. The calculator uses 1,500 pounds per cubic yard, so the 4 by 8 foot example weighs about 1,630 pounds. These are supplier figures, and wet soil weighs more.
| Material | lb per cu yd (Eartheasy) | lb per cu ft at the midpoint | Example bed at the midpoint, lb |
|---|---|---|---|
| Screened topsoil | 2,000 to 2,200 | 77.8 | 2,281 |
| Compost | 1,000 to 1,400 | 44.4 | 1,304 |
| 50/30/20 blend | 1,300 to 1,700 | 55.6 | 1,630 |
Check your pickup truck payload before you haul a full yard.
What this calculator does not cover
This page sizes the soil and frame of a rectangular raised bed. It does not plan plant spacing, yield or watering, and it does not handle L-shaped, round or planter-pot beds. It shows no prices unless you enter them, and it counts no screws, posts or liners.
For a surface cover of wood chips, use the mulch calculator. For new turf around the beds, plan the rolls with the sod calculator. Inputs are in feet and inches. Metric input is not built yet.
Methodology and sources
Published October 2026. Last updated October 2026. Next review October 2027.
Reviews: project calculators · 31 calculators reviewed
Marcus Johnson is a Certified Construction Manager (CCM) with 20 years of experience in residential and commercial site work. He holds CCM certification from CMAA (member #2019-1247). He has managed NALP-member landscape installation projects covering more than 2 million square feet of site work. At CalcSummit, he writes all landscape volume and bulk-material calculators, applying field-tested coverage rates for mulch, gravel, sand, topsoil, and fill dirt.
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