Soil Calculator for Raised Bed

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Raised Bed Soil Calculator

Calculate exactly how much soil, compost, or mulch you need for your garden.

Small Bag (0.75 cu ft) Standard Bag (1.0 cu ft) Large Bag (1.5 cu ft) Extra Large Bag (2.0 cu ft) Compressed Bale (3.0 cu ft)

Results:

Cubic Feet
0
Cubic Yards
0
Total Bags
0

How to Calculate Soil for Your Raised Garden Bed

Planning a garden starts with knowing how much growing medium you need to fill your structures. Whether you are building a standard 4×8 vegetable bed or custom flower boxes, using a soil calculator ensures you don't overspend at the nursery or find yourself short midway through planting.

The Soil Volume Formula

Calculating the volume of a rectangular raised bed is a simple geometry problem. The formula is:

Volume = Length (ft) × Width (ft) × (Depth (inches) / 12)

We divide the depth by 12 to convert inches into feet, resulting in Cubic Feet. To convert Cubic Feet into Cubic Yards (which is how bulk soil is usually sold), divide the total cubic feet by 27.

Example Calculation

If you have a bed that is 8 feet long, 4 feet wide, and 12 inches deep:

  • Step 1: 8 ft × 4 ft × (12 in / 12) = 32 Cubic Feet.
  • Step 2: 32 / 27 = 1.18 Cubic Yards.
  • Step 3: If using 1.5 cu ft bags, you would need 32 / 1.5 = 21.3 (22 bags total).

What Kind of Soil Should You Use?

Standard topsoil is often too heavy for raised beds and can become compacted. For the best results, gardeners typically use the "Raised Bed Mix" approach:

  • 60% Topsoil: The foundation of your bed.
  • 30% Compost: Provides essential nutrients and organic matter.
  • 10% Potting Mix (Peat Moss or Perlite): Improves drainage and aeration.

Pro Tip: Remember that soil settles over time. It is generally wise to order about 5-10% more soil than your calculation suggests to account for compaction and natural settling after the first few waterings.

function calculateSoil() { var length = parseFloat(document.getElementById('bedLength').value); var width = parseFloat(document.getElementById('bedWidth').value); var depthInches = parseFloat(document.getElementById('bedDepth').value); var bagSize = parseFloat(document.getElementById('bagSize').value); var resultsDiv = document.getElementById('soil-results'); if (isNaN(length) || isNaN(width) || isNaN(depthInches) || length <= 0 || width <= 0 || depthInches <= 0) { alert("Please enter valid positive numbers for dimensions."); return; } // Convert depth to feet var depthFeet = depthInches / 12; // Calculate Cubic Feet var totalCuFt = length * width * depthFeet; // Calculate Cubic Yards var totalCuYd = totalCuFt / 27; // Calculate Number of Bags (Round up) var totalBags = Math.ceil(totalCuFt / bagSize); // Update Display document.getElementById('resCuFt').innerText = totalCuFt.toFixed(2); document.getElementById('resCuYd').innerText = totalCuYd.toFixed(2); document.getElementById('resBags').innerText = totalBags; // Show results resultsDiv.style.display = 'block'; }

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