Raised Bed Soil Calculator

Calculate soil needed for raised garden beds with recommended soil mix proportions.

By Konstantin Iakovlev · Updated April 2026 · Source: HomeAdvisor

ft
ft
in

Volume

32.0 cu ft

Bags (1.5 cu ft)

22

Est. Cost

$96.00 - $160.00

Soil Requirements

Cubic Feet32.0 cu ft
Cubic Yards1.19 cu yd
Bags Needed22 bags
Topsoil (60%)19.2 cu ft
Compost (30%)9.6 cu ft
Amendments (10%)3.2 cu ft

Use the Raised Bed Soil Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.

How It Works

Figuring out exactly how much soil a raised bed needs means you buy what the bed takes and leave the waste behind. With raw material costs for soil amendments projected to climb 12% by 2026, getting that number right does real work for your gardening budget. Alongside the volume, the tool suggests mix proportions tuned for healthy, productive plant growth.

Volume comes first, calculated as Length (feet) x Width (feet) x Depth (feet) = Total Volume (cubic feet). On top of that raw figure, a 5% compaction rate is applied, which is standard for most soil types and means the bed will swallow a little more than the bare volume suggests. For the mix itself, the recommended ratio is 60% topsoil, 30% compost, and 10% perlite/vermiculite, a blend known for strong drainage paired with good nutrient retention.

Accurate measurements pay off here, because a small error in length, width, or depth snowballs into ordering far too much or too little soil. Bagged volumes can mislead since compaction varies from bag to bag, so buying in bulk often gives better value and more consistency. One detail that's easy to overlook: any existing drainage layer takes up space and trims the actual soil volume you'll need.

Example: Building a 4'x8' Raised Bed for Tomatoes

  1. 1 Input the dimensions of your raised bed: Length = 8 feet, Width = 4 feet, Depth = 1 foot.
  2. 2 The calculator determines a raw volume of 32 cubic feet (8 x 4 x 1). Applying a 5% compaction factor, you'll need approximately 33.6 cubic feet of soil.
  3. 3 For your 4'x8'x1' raised bed, you will need approximately 33.6 cubic feet of total soil. This breaks down to 20.16 cubic feet of topsoil, 10.08 cubic feet of compost, and 3.36 cubic feet of perlite/vermiculite.
  4. 4 Based on average 2026 prices, this soil mix would cost approximately $375, a significant investment where accurate planning prevents costly errors. This calculation ensures your tomatoes have the perfect growing medium to thrive throughout the season.

Source: HomeAdvisor · Last updated: April 2026

Frequently Asked Questions

How much soil do I need for a 4x8 raised bed?
A 4x8 raised bed that is 12 inches deep needs 32 cubic feet (about 1.2 cubic yards) of soil. This equals roughly 20-25 bags of commercial garden soil at 1.5 cubic feet per bag.
What is the best soil mix for raised beds?
The recommended mix is 60% topsoil, 30% compost, and 10% perlite or coarse sand for drainage. Some gardeners use the "Mel's Mix" of equal parts peat moss, vermiculite, and compost.
How deep should a raised garden bed be?
A minimum of 6 inches for shallow-rooted plants like lettuce and herbs. Most vegetables need 12 inches. Root vegetables like carrots and potatoes do best with 18-24 inches of soil depth.

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