Topsoil Formula Explained: Length × Width × Depth ÷ 27

The Topsoil Formula, Step by Step

Convert depth from inches to feet first. Common depths:

• 2 inches = 0.167 ft
• 4 inches = 0.333 ft
• 6 inches = 0.5 ft
• 12 inches (1 foot) = 1.0 ft

Example (rectangle): 20 ft × 15 ft lawn area, 2 inches of topsoil for overseeding = 20 × 15 × 0.167 = 50.1 cu ft ÷ 27 = 1.86 cubic yards.

Add 10–15% for waste and settling: order 2.1–2.2 cubic yards.

Circular Beds: Use π × Radius²

For round beds, replace length × width with the circle area formula: π × radius². Measure the diameter (full width across), divide by 2 to get the radius, then multiply by itself and by 3.14.

Example (circle): A round bed 8 ft across (radius = 4 ft), filled 6 inches deep with topsoil = 3.14 × 4² × 0.5 = 25.1 cu ft ÷ 27 = 0.93 cubic yards. Order 1 cubic yard with settling allowance.

Irregular Beds: Break Into Rectangles

L-shapes, kidney beans, and free-form beds aren't a single formula. The fastest approach: divide the area into rectangles (and circles), calculate each separately, then add them up. Curves don't need to be exact — round to the nearest rectangle that fits inside the curve.

Example (L-shape): An L-shaped bed that's 10 ft × 4 ft along one side and 6 ft × 3 ft along the other, 4 inches deep:

• Rectangle A: 10 × 4 × 0.333 = 13.3 cu ft
• Rectangle B: 6 × 3 × 0.333 = 6.0 cu ft
• Total: 19.3 cu ft ÷ 27 = 0.71 cubic yards → order 0.85 with waste allowance

For truly irregular shapes, our topsoil calculator lets you add multiple sections in one calculation and totals them automatically.

How Deep to Go

Planning a new lawn? See our full guide on how much topsoil a new lawn needs, including settling allowances and 2026 pricing.

Topsoil Is Heavy — Delivery and Truck Limits Matter

This is where topsoil differs significantly from mulch. One cubic yard of dry topsoil weighs approximately 1,000–1,200 lbs. Wet topsoil can hit 1,400–1,600 lbs per yard — as much as a small car.

A standard half-ton pickup truck (F-150, Silverado, Ram 1500) has a payload capacity of 1,200–2,000 lbs. One yard of topsoil is usually safe, but check your specific truck's payload sticker inside the door jamb. Don't fill the bed based on how it looks — verify the weight limit first.

For orders of 2+ yards, bulk delivery is strongly recommended over multiple pickup trips. Most landscape suppliers can deliver topsoil in the same way as mulch — a dump truck drops a pile on your driveway. See the delivery vs. pickup guide for cost breakdown and logistics.

Topsoil prices in 2026: Basic topsoil runs $15–35 per cubic yard in bulk. Screened topsoil (sifted, higher quality) runs $25–45/yd. Premium blends with compost added can run $40–70/yd. Bags of garden soil (a similar product) are typically $6–9 for 0.75–1 cu ft — far more expensive per yard than bulk.

Topsoil vs. Garden Soil vs. Compost

Topsoil is mineral soil — good for building up a planting area, filling in low spots, or establishing new lawn. It provides structure and volume but limited fertility on its own.

Garden soil (bagged) is topsoil blended with compost and often perlite or other amendments. Better for in-ground beds and raised beds where you want improved drainage and fertility. The volume formula is identical.

Compost is decomposed organic matter — used to amend and improve existing soil rather than build volume. Applied at 1–3 inches, it improves soil biology, drainage, and water retention. For a vegetable garden bed or lawn renovation, mixing 2–3 inches of compost into the top 6 inches of soil makes a significant difference.

For projects that need both volume and soil improvement, mixing bulk topsoil 50/50 with compost is a cost-effective way to get better results than topsoil alone. The calculation works the same — just calculate total volume needed and split the order.

Using the Calculator for Topsoil

Our mulch calculator works perfectly for topsoil — the math is identical. Enter your area shape and dimensions, enter your depth, and it calculates cubic yards. For topsoil, ignore the "bags" section (topsoil is almost always sold in bulk, not bags) and focus on the cubic yards result.

Add 10–15% to your calculated volume before ordering — topsoil settles over time, especially in new beds. If you're filling a 12-inch deep raised bed, order for 14 inches to account for settling and compaction during installation.

Need the bigger picture on cubic yards? Our pillar guide on cubic yards in landscaping covers bag conversions, weight by material, and pickup truck loads in one reference.