Raised Bed Soil Calculator

The Raised Bed Soil Calculator estimates the soil mix needed to fill a rectangular raised garden bed. It converts length, width, and depth into cubic feet, cubic yards, and liters, then applies optional fill ratio and post-watering settling adjustments so the result matches how gardeners actually buy soil.

Raised Bed Soil Formula

For a rectangular bed, soil volume is calculated as length × width × depth. All dimensions are converted to feet first, so a bed that is 8 ft long, 4 ft wide, and 12 in deep is calculated as 8 × 4 × 1 = 32 cubic feet before any settling allowance.

If you use a fill ratio or settling allowance, the calculator applies this adjusted formula: base volume × fill ratio × (1 + settling allowance). A 15% settling allowance means the calculator adds 15% more mix to the target fill volume.

How to Use the Raised Bed Soil Calculator

1. Measure the inside dimensions: Measure the inside length and width of the raised bed, then measure the soil depth you want to fill.
2. Choose the units: Select the unit for each dimension, such as feet for length and width and inches for depth.
3. Set fill and settling adjustments: Use fill ratio for partial beds and add a settling allowance if the mix will compact after watering.
4. Review the soil plan: Click Calculate Soil to see cubic feet, cubic yards, liters, bag counts, and a soil mix breakdown.

Common Raised Bed Soil Volumes

Choosing Soil Depth

Leafy greens and herbs often grow well with 6 to 8 inches of quality soil. Many vegetables are more comfortable with 10 to 12 inches. Deep-rooted crops, dry climates, and beds placed on hard surfaces may benefit from 15 to 18 inches or more.

Bagged Soil vs Bulk Soil

Bagged raised bed soil is convenient for small beds and top-offs, and the package usually lists volume in cubic feet or liters. Bulk soil is usually priced by the cubic yard and can be more practical for larger beds. One cubic yard equals 27 cubic feet, so even a modest group of beds can quickly reach bulk-delivery volume.

Soil Mix Notes

A productive raised bed mix usually balances mineral soil, compost, and drainage. Too much compost can settle heavily, while too much dense topsoil can drain slowly. The mix breakdown in the calculator is a planning estimate; adjust it for local soil, crop needs, and the ingredients available near you.

Frequently Asked Questions

How do I calculate soil for a raised bed?

Multiply the inside length by the inside width by the desired soil depth, using the same unit for each measurement. The calculator converts the result to cubic feet, cubic yards, and liters.

Should I include a settling allowance?

Yes, if the soil mix is fluffy, compost-rich, or newly watered. A 10% to 20% allowance is a common planning range because fresh raised bed mixes often settle after watering and light tamping.

What fill ratio should I use?

Use 100% when filling to the planned soil depth. Use a lower fill ratio when topping off an existing bed, leaving room for mulch, or filling only part of the bed.

How many soil bags do I need?

Divide the adjusted soil volume by the bag volume printed on the package. The calculator shows common 1 cubic foot, 1.5 cubic foot, 2 cubic foot, and 40 liter bag estimates.

Is raised bed soil measured in cubic feet or cubic yards?

Bagged soil is often sold in cubic feet or liters, while bulk soil deliveries are commonly sold in cubic yards. The same volume can be converted between all three units.