Garden Bed Soil Calculator
Estimate cubic yards of soil mix and total cost for new or refreshed garden beds. Use it when building raised beds or amending existing garden plots before planting season.
About this calculator
The calculator first converts your bed dimensions to cubic yards: volume (yd³) = (length × width × (depth / 12)) / 27. The result is rounded up to the nearest tenth to avoid under-ordering. A soil-type multiplier and an amendments multiplier are then applied to account for bulking from compost or other additives: adjusted volume = base volume × (1 + soilType + amendments). Finally, a flat delivery fee is added to give the total cost. This approach captures both the raw material volume you need and the price to get it to your property, so you can compare suppliers at a glance.
How to use
Suppose you are building a bed that is 8 ft long × 4 ft wide × 12 inches deep, using a premium soil mix (soilType = 0.2), with compost amendments (amendments = 0.1), and a $50 delivery fee. Base volume = (8 × 4 × (12 / 12)) / 27 = 32 / 27 ≈ 1.2 yd³. Rounded to one decimal: 1.2. Adjusted volume = 1.2 × (1 + 0.2 + 0.1) = 1.2 × 1.3 = 1.56 yd³. Add delivery: 1.56 + 50 = $51.56 total estimated cost.
Frequently asked questions
How many cubic yards of soil do I need for a 4×8 raised garden bed?
A 4 ft × 8 ft raised bed filled to 12 inches deep requires (4 × 8 × 1) / 27 ≈ 1.19 cubic yards of soil. If you fill it only 6 inches deep, that drops to about 0.6 cubic yards. Always round up slightly when ordering bulk soil to account for settling after watering. The calculator handles this rounding automatically.
What is a soil amendment multiplier and why does it affect the total volume?
Soil amendments such as compost, perlite, or bark fines add bulk to your soil mix beyond the raw topsoil volume. The amendment multiplier represents the fractional increase in total material needed — for example, 0.1 means 10% more material. Adding amendments improves drainage, aeration, and nutrient content, so the extra volume is worth the cost. The calculator folds this multiplier into the adjusted cubic-yard figure so you order enough of the blended mix.
When should I add a delivery fee to my garden bed soil estimate?
Include a delivery fee whenever you are ordering bulk soil by the cubic yard from a landscape supplier rather than buying bagged soil at a garden center. Bulk delivery fees typically range from $30 to $100 depending on distance and supplier. Entering the fee here lets you compare the true landed cost of bulk versus bagged soil side by side. For small beds under 1 cubic yard, bagged soil is often cheaper once delivery is factored in.