One of the most common questions in landscaping is: "How many cubic yards do I need?"

Whether you're ordering topsoil, mulch, compost, or landscape rock, getting the calculation right saves money, prevents waste, and ensures your project goes smoothly.

The good news? The math is simple. A single formula works for nearly every situation.

This guide walks you through the formula, shows you step-by-step examples, and includes a calculator table for quick reference.

The Cubic Yard Formula

Cubic Yards = Length (ft) × Width (ft) × Depth (ft) ÷ 27

That's it. Three measurements and one division.

Why Divide by 27?

One cubic yard = 27 cubic feet.

So when you multiply length × width × depth in feet, you get cubic feet. Divide by 27 to convert to cubic yards.

Step-by-Step: How to Calculate

Step 1: Measure Length and Width

Measure your garden bed, lawn area, or landscape space in feet. Be as accurate as possible.

  • For rectangular beds: easy — just measure the sides
  • For circular beds: measure the diameter, then use the circle formula (see below)
  • For irregular beds: break them into rectangles, calculate each, then add

Step 2: Measure Depth

Decide how deep you want your material (mulch, topsoil, etc.). Common depths:

Convert inches to feet:

  • 2 inches = 0.17 feet
  • 3 inches = 0.25 feet
  • 4 inches = 0.33 feet
  • 6 inches = 0.5 feet

Step 3: Multiply and Divide

Plug your numbers into the formula:

Cubic Yards = Length (ft) × Width (ft) × Depth (ft) ÷ 27

Step 4: Round Up and Add Buffer

Always round up. Materials settle, and you want full coverage.

Add 10-15% extra to account for settling and spillage.

Real Examples

Example 1: Rectangular Raised Bed

You have a raised bed that's:

  • 4 feet long
  • 8 feet wide
  • 12 inches (1 foot) deep

Calculation:

  • 4 × 8 × 1 = 32 cubic feet
  • 32 ÷ 27 = 1.19 cubic yards
  • Round up + 10%: Order 1.5 cubic yards

Example 2: Mulch for a Garden Bed

Your garden bed is:

  • 10 feet long
  • 5 feet wide
  • 3 inches (0.25 feet) deep

Calculation:

  • 10 × 5 × 0.25 = 12.5 cubic feet
  • 12.5 ÷ 27 = 0.46 cubic yards
  • Round up + 10%: Order 0.5 cubic yards

Example 3: Large Lawn Area

You're topdressing a lawn that's:

  • 50 feet long
  • 40 feet wide
  • 2 inches (0.17 feet) deep

Calculation:

  • 50 × 40 × 0.17 = 340 cubic feet
  • 340 ÷ 27 = 12.6 cubic yards
  • Round up + 10%: Order 14 cubic yards

Example 4: Circular Bed

You have a circular flower bed with:

  • Diameter of 6 feet (radius = 3 feet)
  • Depth of 3 inches (0.25 feet)

Formula for circles:

  • Area = π × radius²
  • Area = 3.14 × 3² = 28.26 square feet
  • Volume = 28.26 × 0.25 = 7.07 cubic feet
  • Cubic yards = 7.07 ÷ 27 = 0.26 cubic yards
  • Round up + 10%: Order 0.35 cubic yards

Quick Reference: Common Project Sizes

Use this table for quick calculations. All values include 10% buffer.

Rectangular Garden Beds

Bed Size 2" Deep 3" Deep 4" Deep 6" Deep
4×4 ft 0.12 yd 0.18 yd 0.24 yd 0.37 yd
4×8 ft 0.25 yd 0.37 yd 0.49 yd 0.74 yd
4×10 ft 0.31 yd 0.46 yd 0.62 yd 0.92 yd
5×10 ft 0.38 yd 0.57 yd 0.77 yd 1.15 yd
5×20 ft 0.76 yd 1.15 yd 1.53 yd 2.30 yd
10×10 ft 0.75 yd 1.11 yd 1.48 yd 2.30 yd
10×20 ft 1.49 yd 2.22 yd 2.96 yd 4.44 yd
20×20 ft 2.99 yd 4.44 yd 5.92 yd 8.88 yd
25×50 ft 7.48 yd 11.11 yd 14.81 yd 22.22 yd
1,000 sq ft lawn 7.41 yd 11.11 yd 14.81 yd 22.22 yd

Circular Beds (by Diameter)

Diameter 2" Deep 3" Deep 4" Deep 6" Deep
4 ft 0.08 yd 0.12 yd 0.16 yd 0.25 yd
6 ft 0.18 yd 0.27 yd 0.36 yd 0.55 yd
8 ft 0.32 yd 0.48 yd 0.64 yd 0.96 yd
10 ft 0.50 yd 0.75 yd 1.00 yd 1.50 yd
12 ft 0.72 yd 1.08 yd 1.44 yd 2.16 yd
15 ft 1.13 yd 1.69 yd 2.25 yd 3.38 yd
20 ft 2.00 yd 3.00 yd 4.00 yd 6.00 yd

Pro Tips for Ordering

Tip 1: Always Round Up

Don't calculate exactly and order the exact amount. Order 1-2 cubic yards extra. You'll either use it or have a small buffer for settling.

Tip 2: Account for Settling

Mulch and compost settle 10-20% after delivery. If you need full coverage for a year, order extra.

Tip 3: Break Irregular Shapes into Rectangles

If your bed is an odd shape, divide it into rectangles, calculate each, then add together.

Tip 4: Confirm Depth Before Ordering

Different projects need different depths:

  • Mulch: 3 inches (standard)
  • Topsoil for lawns: 4-6 inches
  • Topsoil for gardens: 6-8 inches
  • Soil amendment: 2-3 inches

Ask your supplier if unsure.

Tip 5: Get Soil Analysis

When ordering soil, ask for soil analysis showing:

  • Organic matter %
  • pH
  • Nutrient levels
  • Contaminants

This ensures you're getting quality product.

How to Order Cubic Yards

When Ordering by Phone or Online

"I need topsoil for a garden bed that's 10 feet by 5 feet, 3 inches deep. Can you deliver?"

Supplier will calculate: 10 × 5 × 0.25 ÷ 27 = 0.46 yd. They'll likely round to 0.5 yd.

When Ordering Online (Using a Calculator)

Many landscape suppliers have online calculators. You input:

  • Length (feet)
  • Width (feet)
  • Depth (inches)
  • Product type (topsoil, mulch, compost)

The site calculates cubic yards and cost.

When Ordering Large Projects

For big projects (20+ cubic yards), ask about:

  • Bulk discounts
  • Delivery fees (often free over 10 yards)
  • Dump truck vs. smaller deliveries
  • Same-day delivery availability

Common Ordering Mistakes

Mistake 1: Confusing Tons with Cubic Yards

Mulch is often priced by weight (tons), not volume (cubic yards).

Example: 1 cubic yard of mulch ≈ 500 lbs ≈ 0.25 tons.

Always clarify with supplier whether they price by yard or ton.

Mistake 2: Forgetting to Convert Inches to Feet

The formula requires feet. If depth is in inches, convert first:

  • 2 inches = 0.17 feet
  • 3 inches = 0.25 feet
  • 4 inches = 0.33 feet

Mistake 3: Underestimating Project Size

Always add 10-15% extra. Materials settle, you might spill, and you want full coverage.

Mistake 4: Not Accounting for Slope

If your bed slopes, use the average depth:

  • Shallow end: 2 inches
  • Deep end: 4 inches
  • Average: 3 inches ← Use this

Mistake 5: Ordering Different Materials Without Converting

Topsoil, mulch, and compost settle differently:

  • Mulch: settles 10-15%
  • Topsoil: settles 5-10%
  • Compost: settles 15-20%

If you're layering materials, order more compost than mulch.

FAQ: Cubic Yard Calculations

Q: How many cubic feet are in a cubic yard?
A: 27 cubic feet = 1 cubic yard.

Q: Can I use a cubic yard calculator online?
A: Yes. Most landscape suppliers have them. Just input your dimensions and the calculator does the math.

Q: What if my measurements aren't exact?
A: Round to the nearest foot. Minor variations are absorbed by the 10-15% buffer you're ordering extra.

Q: Do I need the exact amount?
A: No. Always order extra. Soil settles 5-20%, and you'll want a buffer for repairs or future projects.

Q: How do I calculate for slopes or varied depth?
A: Use the average depth. Measure the shallowest and deepest points, average them, then use the formula.

Q: Can mulch weight be converted to cubic yards?
A: Sort of. Roughly 1 cubic yard of mulch = 500 lbs. But this varies by mulch type. Ask your supplier.

Q: What if I miscalculate and order too much?
A: Keep it. You'll use it for topping off next year, or offer to friends/neighbors.

Q: What if I order too little?
A: Call your supplier. Many offer small follow-up deliveries at reduced cost.

The Bottom Line

The cubic yard formula is simple:

Length × Width × Depth (in feet) ÷ 27 = Cubic Yards

Measure carefully, convert inches to feet, and always order 10-15% extra. You'll get the right amount, and your project will go smoothly.

Ready to Order? Use Our Soil Calculator

At Harbor Soils, we deliver mulch, topsoil, compost, and landscape materials to Gig Harbor and Kitsap County. Use our online calculator to get your cubic yard estimate, then order same-day delivery with no minimums.

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