You will measure your project in feet, but the supplier will quote you in yards — and mixing the two up is the most expensive beginner mistake in DIY estimating. This guide walks through the one conversion you need, with a worked example you can follow along.
Step-by-step: convert with confidence
- Measure in feet first. Length × width × depth (in feet) gives you cubic feet.
- Remember the magic number: 27. One cubic yard = 27 cubic feet (3 × 3 × 3).
- Divide by 27. Cubic feet ÷ 27 = cubic yards — the unit suppliers quote.
- Watch your depth units. A 4-inch slab is 4 ÷ 12 = 0.333 ft. Mixing inches and feet is the #1 mistake.
- Sanity-check the size. A full pickup bed holds roughly 2 cubic yards — if your answer says 40, recheck.
Example calculation
Depth in feet: 4 ÷ 12 = 0.333 ft.
Cubic feet: 20 × 15 × 0.333 = 100 ft³.
Cubic yards: 100 ÷ 27 = 3.70 yd³ → +5% waste = 3.89 yd³ to order.
Quick reference
- 1 yd³ = 27 ft³
- 1 ft³ ≈ 0.037 yd³
- 80-lb bag of concrete ≈ 0.6 ft³ (≈ 45 bags per yd³)
Also handy: Gravel Calculator · Mulch Calculator · Unit Conversions
Frequently asked questions
How many cubic feet are in a cubic yard?
Exactly 27. Picture a cube 3 feet on each side: 3 × 3 × 3 = 27 cubic feet. To convert cubic feet to cubic yards, divide by 27.
Why do suppliers quote cubic yards when I measured in feet?
Bulk materials like ready-mix concrete, gravel and mulch are sold by the truckload, and trucks are rated in cubic yards. Knowing the conversion lets you check a supplier's quote against your own measurements.
Does the concrete calculator handle this conversion for me?
Yes — enter dimensions in feet and inches and it converts to cubic yards automatically. This guide is for sanity-checking supplier quotes and for materials where you are doing the math by hand.