How far will the soil I have go?
Already bought bags or a yard? Enter what you have and the depth to see how much bed it fills.
How the raised bed soil calculator works
The calculator finds the area of each bed, multiplies by how many identical beds you have, and multiplies by the fill depth. It adds a settling allowance, then converts the total to cubic feet, cubic yards, cubic meters and liters. Bag counts, weight and delivery loads come from that one volume, and the mix splitter divides it into topsoil, compost and other ingredients by percentage.
With extra = volume × (1 + extra %)
Cubic yards = cubic feet ÷ 27
Each ingredient = total × its percentage
Area formulas used for each shape
| Shape | Formula |
|---|---|
| Rectangle | length × width |
| Circle | π × (diameter ÷ 2)² |
| Triangle | ½ × base × height |
| Known area | entered directly in sq ft (or sq m if you chose meters) |
Worked examples
Example 1: a 4 × 8 ft bed, 10 inches deep
4 × 8 = 32 sq ft. At 10 in (⅚ ft) that is 26.7 cu ft, or 29.3 cu ft with 10% extra. That is 1.09 cubic yards, or 30 bags of 1 cu ft. A 60/30/10 mix is about 17.6 cu ft of topsoil, 8.8 of compost and 2.9 of sand or similar.
Example 2: a 3 × 6 ft bed, 12 inches deep
3 × 6 = 18 sq ft. At 12 in that is 18 cu ft, or 19.8 cu ft with 10% extra. That is 0.73 cubic yards, or 20 bags of 1 cu ft. At this size bags are practical, but a yard of bulk mix may still cost less.
Example 3: a round bed 4 ft across, 12 inches deep
Area = π × 2² = 12.6 sq ft. At 12 in that is 12.6 cu ft, or 13.8 cu ft with 10% extra. That is 0.51 cubic yards, or 14 bags of 1 cu ft.
Example 4: three 4 × 8 ft beds, 12 inches deep
Set "How many?" to 3. 32 sq ft × 3 = 96 sq ft, so 96 cu ft, or 105.6 with 10% extra. That is 3.9 cubic yards, so ask for 4 yards in bulk. In 1 cu ft bags it would be 106 bags, which is why bulk wins at this size.
How much soil common raised beds hold
| Bed size | At 6 in | At 8 in | At 12 in | Cubic yards at 12 in |
|---|---|---|---|---|
| 4 × 4 ft (16 sq ft) | 8 cu ft | 10.7 cu ft | 16 cu ft | 0.59 |
| 3 × 6 ft (18 sq ft) | 9 cu ft | 12 cu ft | 18 cu ft | 0.67 |
| 4 × 8 ft (32 sq ft) | 16 cu ft | 21.3 cu ft | 32 cu ft | 1.19 |
| 4 × 12 ft (48 sq ft) | 24 cu ft | 32 cu ft | 48 cu ft | 1.78 |
These are before the settling allowance. Add about 10% to order.
How deep should the soil be?
| Crops | Typical soil depth |
|---|---|
| Salad greens, herbs, radishes, spinach | 6 to 8 in |
| Beans, peppers, cucumbers, kale, onions | 10 to 12 in |
| Tomatoes, carrots, parsnips, potatoes | 12 to 18 in |
| Berries, small shrubs | 18 to 24 in |
These are common guides. A bed built on open ground lets roots grow below the frame, so it needs less fill.
Common raised bed soil mixes
| Mix | Topsoil | Compost | Other |
|---|---|---|---|
| Basic all-round mix | 60% | 30% | 10% coarse sand, perlite or similar |
| Rich vegetable mix | 50% | 50% | none |
| Light mix (square-foot style) | none | about 33% | about 67% coir or peat moss and vermiculite |
Enter the first two columns in the splitter. For the light mix, put the combined other ingredients in the last box. These are popular starting points rather than rules.
Mistakes to avoid
- Measuring the wall height instead of the fill depth. Fill to an inch or two below the rim. Enter the depth of the soil, not the height of the frame.
- Filling with pure compost. Pure compost can be too rich and shrinks fast. Mix it with topsoil, and keep it to about a third to a half of the total.
- Forgetting settling. Loose mixes sink after watering. A 10% allowance avoids a second delivery, and you can top up later.
- Mixing up depth units. 10 inches is ⅚ foot, not 10. Pick the depth unit in the tool and check the result looks sensible.
- Buying a lot of bags for a big bed. Bags are handy for one or two small beds. Past about a cubic yard, price bulk delivery or a bulk soil and compost mix.
How far does a bag or a yard of soil go in a raised bed?
Coverage depends on how deep you fill: the same soil fills half as much area when it is twice as deep. This table uses bags of 1 cubic foot. Check the cubic feet printed on your bag, and use the calculator above for your exact bed.
| You have | Covers at 6 in deep | Covers at 10 in deep | Covers at 12 in deep | Covers at 18 in deep |
|---|---|---|---|---|
| 10 bags (1 cu ft each) | 20 sq ft | 12 sq ft | 10 sq ft | 7 sq ft |
| 27 bags (about 1 cubic yard) | 54 sq ft | 32 sq ft | 27 sq ft | 18 sq ft |
| 2 cubic yards | 108 sq ft | 65 sq ft | 54 sq ft | 36 sq ft |
| 3 cubic yards | 162 sq ft | 97 sq ft | 81 sq ft | 54 sq ft |
| 5 cubic yards | 270 sq ft | 162 sq ft | 135 sq ft | 90 sq ft |
No settling allowance is included here. Add about 10%.
Frequently asked questions
How much soil do I need for a raised bed?
Multiply length × width × depth (all in feet) to get cubic feet, add about 10% for settling, then divide by 27 for cubic yards. A 4 × 8 ft bed filled 10 inches deep holds 26.7 cubic feet, or about 29.3 with 10% extra. That is roughly 1.1 cubic yards.
How many cubic feet is a 4x8 raised bed?
It depends on how full you fill it. A 4 × 8 ft bed is 32 square feet, so it holds 16 cubic feet at 6 inches, 21.3 at 8 inches, 26.7 at 10 inches and 32 at 12 inches. Add about 10% to those figures for settling.
What is the best soil mix for raised beds?
A common recipe is about 60% topsoil, 30% compost and 10% coarse sand, perlite or similar to keep it loose. Some gardeners use half topsoil and half compost, and others use a lighter blend of compost, coir or peat, and vermiculite. Local conditions and the crop matter, so treat these as starting points.
How deep should a raised bed be?
Six to eight inches is enough for salad greens and herbs. Most vegetables do well in 10 to 12 inches, and deep-rooted crops such as tomatoes, carrots and potatoes like 12 to 18 inches. If the bed sits on loose ground, roots can also grow into the soil underneath, so it does not all have to be filled with bought soil.
How much extra soil should I order for settling?
About 10% extra is a common allowance, and some gardeners add up to 20% for new beds filled with fluffy compost-rich mixes. Soil sinks after the first few waterings, and you can top it up in a few weeks. The calculator adds 10% and lets you change it.
Can I fill the bottom of a deep raised bed with logs or branches?
Many gardeners do, to save on soil in beds 18 inches or deeper. Use rotting logs, sticks, leaves or cardboard, and cover them with at least 8 to 10 inches of good soil for roots. The wood shrinks as it breaks down, so expect the bed to settle more and top it up. Count only the soil layer in the calculator.
How many bags of soil does a 4x4 raised bed need?
A 4 × 4 ft bed is 16 square feet. At 10 inches deep it holds 13.3 cubic feet, or 14.7 with 10% extra for settling. That is about 20 bags of 0.75 cubic feet or 15 bags of 1 cubic foot. At 12 inches deep it is 16 cubic feet, or 17.6 with 10% extra.
How much soil do I need for a 4x8 raised bed that is 12 inches deep?
A 4 × 8 ft bed at 12 inches deep holds 32 cubic feet, which is 1.19 cubic yards. With 10% extra for settling that is 35.2 cubic feet, or 1.3 cubic yards, so a 1.5 yard bulk order leaves some spare. In bags that is about 47 bags of 0.75 cubic feet.
How many cubic yards of soil do I need for a 3x6 raised bed?
A 3 × 6 ft bed is 18 square feet. At 12 inches deep that is 18 cubic feet, or 0.67 cubic yards. At 9 inches it is 13.5 cubic feet, or 0.5 cubic yards, and at 6 inches it is 9 cubic feet, or 0.33 cubic yards. Add about 10% for settling.
How do I work out soil for a round raised bed?
Find the area with π × radius², where the radius is half the width, then multiply by the depth in feet. A bed 4 ft across and 12 inches deep is π × 2² × 1 = 12.6 cubic feet. Choose the Circle shape in the calculator and enter the diameter.
How much does a cubic yard of raised bed soil weigh?
It depends on what is in it. The calculator uses 60 pounds per cubic foot, about 1,600 pounds per cubic yard, for a loose raised bed mix. Compost-heavy mixes are lighter, and topsoil-heavy or wet mixes can be well over a ton. Ask your supplier for their figure before you plan a delivery.
Should I put cardboard at the bottom of a raised bed?
Many gardeners lay plain cardboard on grass or weeds before filling the bed, because it blocks light and breaks down within a season while letting roots and worms through. Remove tape and glossy print. If gophers or moles are a problem, a layer of hardware cloth under the bed is the usual fix.
Is bulk soil cheaper than bags for a raised bed?
Usually, once you need about a cubic yard or more. A yard equals 27 bags of 1 cubic foot, so bags add up fast, but bulk may carry a delivery fee or minimum order. Enter your bag and bulk prices in the calculator to compare for your own bed.
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