This topsoil calculator works out the volume of topsoil you need for a lawn, garden bed, or landscaping project. Enter the length and width of the area in feet, the depth you want in inches, and it returns the volume in cubic yards and cubic feet. The result tells you exactly how much soil to order, so you avoid both shortages and costly over-ordering.
Formula
The calculator uses the standard volume formula for a rectangular prism: Volume = length × width × depth. Since the inputs are in feet and inches, the formula converts depth from inches to feet by dividing by 12, then divides by 27 to convert cubic feet to cubic yards (because 1 cubic yard = 27 cubic feet).
In symbols: V (yd³) = L (ft) × W (ft) × D (in) ÷ 324. The 324 comes from 12 inches per foot × 27 cubic feet per cubic yard. The second output, cubic feet, is simply L × W × D ÷ 12.
Worked Example
Using the default values from the calculator block: length = 40 ft, width = 25 ft, depth = 3 in.
- Convert depth to feet: 3 in ÷ 12 = 0.25 ft
- Calculate volume in cubic feet: 40 × 25 × 0.25 = 250 ft³
- Convert to cubic yards: 250 ÷ 27 = 9.26 yd³ (rounded to 2 decimal places)
The calculator shows 9.26 cubic yards and 250.0 cubic feet, matching the manual calculation.
Why Depth Matters More Than You Think
Most topsoil calculators ask for depth because it is the single biggest factor in volume. A 1-inch difference over a 1,000 sq ft area changes the volume by over 3 cubic yards. For lawns, 3–4 inches of new topsoil is typical for leveling and improving drainage. For garden beds, 6–12 inches is common, depending on what you are planting. If you are only adding a thin layer to patch bare spots, 1–2 inches may be enough. Always match the depth to the purpose, not to what the bag says.
A common mistake is mixing units: if you enter depth in feet instead of inches, the result will be 12 times too large. Always double-check that your depth is in inches when using this calculator.
How to Measure Your Area
For a rectangular lawn or bed, measure length and width with a tape measure. For irregular shapes, break the area into rectangles and triangles, calculate each separately, then add the volumes. For a circle, measure the radius (half the diameter) and use πr² for the area, then multiply by depth. If your area is a long, winding border, it is often easier to approximate it as a rectangle and add 10% extra.
If you are ordering from a bulk supplier, they typically deliver in cubic yards. If you are buying bags from a garden center, bags are usually sold in cubic feet (e.g., 1.5 or 2 cu ft). To convert cubic yards to bags, multiply by 27 and divide by the bag size. For example, 9.26 yd³ × 27 = 250 ft³; if each bag is 2 ft³, you need 125 bags. That is a lot of bags – for large projects, bulk delivery is usually more practical.
Common Mistakes and How to Avoid Them
- Mixing units: Always use feet for length and width, inches for depth. If you measure in meters, convert to feet first (1 m = 3.28084 ft).
- Rounding too early: Do not round the depth to 0.3 ft if you measured 3.5 inches – use 3.5/12 = 0.2917 ft. Small errors compound over large areas.
- Forgetting compaction: Fresh topsoil settles after watering. Order about 10–15% extra to account for compaction, especially for lawns.
- Assuming all topsoil is the same: Screened topsoil has a finer texture and fewer rocks, but it costs more. Unscreened soil may contain clods and debris, which can affect volume and quality.
Topsoil vs. Other Soil Types
Topsoil is the upper layer of soil, rich in organic matter and microorganisms. It is different from fill dirt (subsoil, low in nutrients), compost (fully decomposed organic matter), and garden soil (a blend of topsoil and compost). For raised beds, a mix of topsoil and compost is often recommended. For leveling a lawn, plain topsoil is fine. If you are planting vegetables, you may want a higher organic content. The calculator works for any of these materials – the volume is the same, but the weight and price vary.
Cost and Ordering Considerations
Topsoil is sold by volume, not weight, but weight matters for delivery and handling. A cubic yard of dry topsoil weighs about 1,000–1,200 lbs, but wet soil can weigh up to 1,500 lbs per cubic yard. When ordering, ask about delivery fees and minimum order quantities. Many suppliers require a minimum of 1–2 cubic yards. If you only need a small amount, bags may be more economical. Always confirm the moisture content – buying by volume means you pay for water, so dry soil is a better deal.
Frequently Asked Questions
How many cubic feet are in a cubic yard?
There are 27 cubic feet in 1 cubic yard (3 ft × 3 ft × 3 ft). To convert cubic feet to cubic yards, divide by 27. The calculator does this automatically.
What depth of topsoil do I need for a new lawn?
For a new lawn, 4–6 inches of topsoil is recommended. This gives grass roots enough room to establish and holds moisture well. For overseeding an existing lawn, 1–2 inches is usually enough.
How much topsoil do I need for a 10×10 garden bed?
For a 10 ft × 10 ft bed at 6 inches deep, the volume is 10 × 10 × 0.5 = 50 ft³, which is about 1.85 yd³. That is roughly 1.9 cubic yards, or about 25 bags of 2 cu ft each.
Can I use this calculator for raised beds?
Yes, the formula is the same. Measure the length, width, and desired depth of the raised bed. If the bed is not rectangular, break it into sections and add the volumes.
Why does the calculator show cubic yards and cubic feet?
Cubic yards is the standard unit for bulk delivery, while cubic feet is common for bagged soil. Showing both lets you compare prices and order the right quantity, whether you buy in bulk or by the bag.