Garden Bed Soil Calculator
Garden bed soil calculator works out Area covered and Depth from Material, Density from your supplier and Length. The default figures on this page give volume of 0.7901 yd3; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
7 steps
- Area = 8 ft x 4 ft = 32 sq ft
- Depth = 8 in = 0.66667 ft
- Volume = 32 x 0.66667 = 21.3333 cu ft = 0.7901 cu yd
- Density = 67.164 lb/ft3 (70% EPA table: Soil/sandy loam, loose - 1 cubic yard - 2,392 lb (Tellus); 2392/27 = 88.593 + 30% EPA table: Compost, loose - 1 cubic yard - 463.39 lb (Tellus); 463.39/27 = 17.163)
- Weight = 21.3333 x 67.164 = 1432.8 lb = 0.716 US short tons
- Blend split: 0.5531 cu yd of the base material plus 0.237 cu yd blended in (EPA table: Compost, loose - 1 cubic yard - 463.39 lb (Tellus); 463.39/27 = 17.163)
- Bags = ceil(21.333 cu ft / 1.5 cu ft) = 15
Figures from bulk material densities, checked 31 August 2026. Its 9 worked examples are re-run on every release, last on 15 September 2026. What changed · how reference data is kept current
Sources and references
4 sources
Keep this result
Save it, change one figure, then compare the two
The calculation stays free. Save this scenario, adjust one assumption, save that too, and put them side by side to see exactly what the change costs you. A free account keeps 5 scenarios and 2 comparisons; Personal makes both unlimited and adds exports and private links. Nothing is saved unless you press Save.
What the garden bed soil calculator calculates
Converts a covered area and spread depth - or a known tonnage, or a measured stockpile - into the volume of gravel, sand, topsoil, mulch, compost or decorative stone required, in cubic feet, cubic yards, cubic metres, bags, tons and tonnes, with a soil-blend split and cost by the yard, the ton or the bag.
How to use this garden bed soil calculator
Enter Material, Density from your supplier, Length and Width. Area covered updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Area covered, Depth and Volume.
The method follows U.S. EPA, Standard Volume-to-Weight Conversion Factors (loose bulk densities for gravel, sand, stone, soil, wood chips and compost), ASTM C29/C29M, Standard Test Method for Bulk Density (Unit Weight) and Voids in Aggregate, NIST Special Publication 811, Guide for the Use of the International System of Units (exact ft-to-m and lb-to-kg conversions) and Interlocking Concrete Pavement Institute, Tech Spec 2: Construction of Interlocking Concrete Pavements (1 in / 25 mm screeded bedding sand course).
What you can compare
Change one input at a time to see how it affects Area covered, Depth and Volume. The inputs you can vary are Material, Density from your supplier, Length, Width, Unit for the plan dimensions and Depth of the layer.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How do I calculate how much soil I need for a garden bed?
Converts a covered area and spread depth - or a known tonnage, or a measured stockpile - into the volume of gravel, sand, topsoil, mulch, compost or decorative stone required, in cubic feet, cubic yards, cubic metres. Open “How this is worked out” beside the result to see each step for your own figures.
How many 40lb bags of soil equal 1 yard?
On the figures this page opens with — length 20, width 10, depth of the layer 4 and extra for compaction, settlement and spillage 0% — the volume is 0.7901 yd3. No single number fits everyone: change any figure above and the answer updates as you type, with each step of the arithmetic beside it.
How many bags of soil do I need for a 4x8 raised bed?
It needs Material, Density from your supplier, Length, Width, Unit for the plan dimensions and Depth of the layer. Nothing else is required, and the figures stay in your browser.
What information do I need for the garden bed soil calculator?
You need Material, Density from your supplier, Length, Width, Unit for the plan dimensions, Depth of the layer, Unit for the depth and How many identical areas. The page opens with default figures that give volume of 0.7901 yd3, so you can see the scale before entering your own.
What does this garden bed soil calculator show?
It shows Area covered, Depth, Volume, Order this much (rounded up to the half yard), Bulk density used, Weight, Bags needed and Order this much (rounded up to the half ton), with the working and any warnings for your entries.
Can I check how the garden bed soil calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.