How this instrument works
A cubic yard is the standard order unit for bulk construction and landscaping materials in the United States — concrete, gravel, sand, mulch and topsoil are all priced and delivered by the yard rather than the cubic foot, because a cubic foot is an awkwardly small unit for a dump-truck load. One cubic yard equals exactly 27 cubic feet, since a yard measures 3 feet on a side and 3 × 3 × 3 = 27.
This instrument takes the three dimensions of a rectangular excavation, fill area or slab — length, width and depth, all in feet — multiplies them together to get cubic feet, then divides by 27 to convert straight to cubic yards. It is deliberately kept to plain rectangular geometry: an L-shaped bed, sloped yard, or stepped excavation needs breaking into separate rectangular sections and summing the results, one calculation per section.
Depth is the dimension most often mismeasured, because it is commonly specified in inches on a landscaping plan or mulch bag but this instrument expects feet. A 4 in depth is 4/12 = 0.333 ft, and a 2 in depth is 2/12 = 0.167 ft — converting to feet before entering the value keeps the final cubic-yard figure accurate rather than off by a factor of twelve.
- Enter Length (ft) and Width (ft) for the rectangular area you're excavating, filling or paving.
- Enter Depth (ft) — convert from inches first if your plan specifies inches: divide the inch figure by 12.
- Read Volume (cubic yards) directly beneath the inputs; it recalculates the instant any field changes.
- For an irregular footprint, split it into rectangular sections, run each through this instrument separately, and add the results together.
- Round the total up before ordering — most suppliers deliver in fixed truck loads or minimum-yardage increments, and loose materials like gravel or mulch settle and compact after placement.
Worked example — a 10 ft × 10 ft × 1 ft excavation
Enter 10 into Length (ft), 10 into Width (ft) and 1 into Depth (ft) — a 10-by-10-foot patch dug one foot deep, a common small-footing or garden-bed excavation. Length × width × depth = 10 × 10 × 1 = 100 cubic feet.
Volume (cubic yards) reads 3.7037 — 100 cubic feet divided by 27. A supplier would round that up to roughly 4 cubic yards to cover the shortfall a bare calculation always leaves once loose material is dumped, spread and compacted.
Questions
Why divide by 27 to get cubic yards?
Because 1 cubic yard equals exactly 27 cubic feet — a yard is 3 feet long on each of its three dimensions, and 3 × 3 × 3 = 27. Multiplying length, width and depth in feet gives a volume in cubic feet, so dividing that figure by 27 converts it to the cubic-yard unit that concrete, gravel, mulch and topsoil are actually sold and delivered in.
What if I already know my area in square feet instead of length and width?
Use this site's dedicated square-feet-to-cubic-yards instrument instead, which takes an area and a depth in inches directly rather than requiring you to re-derive length and width. Both instruments compute the identical volume; this one is built for when you're measuring a rectangle from scratch, the other for when a plan or listing already gives you a total square footage.
My depth is given in inches — do I need to convert it first?
Yes. This instrument's Depth field expects feet, so divide an inch measurement by 12 before entering it — a 4 in gravel layer becomes 0.333 ft, and a 6 in slab becomes 0.5 ft. Entering inches directly into a feet field overstates the volume by a factor of 12, a common and easy-to-miss ordering mistake.
Should I order exactly the calculated amount?
No — order a little more. Loose materials like gravel, mulch and topsoil compact after delivery and placement, typically losing 10–20% of their loose volume, and concrete pours commonly get a 5–10% buffer for spillage and an uneven sub-base. Suppliers also deliver in fixed truck loads or minimum increments, so the practical order is usually the calculated figure rounded up, not rounded to the nearest tenth.
How do I handle an L-shaped or irregular area?
Split the footprint into two or more rectangles that together cover the whole area, run each rectangle through this instrument with its own length, width and depth, and add the resulting cubic-yard figures together. The formula itself only handles a single rectangular box at a time, so irregular shapes always need this kind of manual decomposition first.