How to Determine Concrete Yardage for Any Project | Concrete Yardage

How to Determine Concrete Yardage for Any Project

Ordering the wrong amount of concrete is one of the most expensive mistakes in construction. Too little means a cold joint and an emergency second delivery (with short-load fees of $150+). Too much means you're paying for material that ends up in a dumpster at the end of the day. Knowing how to determine concrete yardage accurately saves hundreds of dollars on every project.

This guide walks you through the exact formula with real-world examples for slabs, footings, columns, and odd-shaped pours - so you can order with confidence.

The Core Formula for Determining Concrete Yardage

The basic formula is simple:

Volume (yd³) = Length (ft) × Width (ft) × Depth (ft) ÷ 27

Divide by 27 because there are 27 cubic feet in one cubic yard. That's it. Everything below is applying this formula to different project types and adding the safety margin that professionals use.

Step-by-Step: Standard Rectangular Slab

Let's say you're pouring a 12×16 patio at 4 inches thick:

1. Convert inches to feet: 4 inches ÷ 12 = 0.333 ft
2. Calculate cubic feet: 12 × 16 × 0.333 = 64 cubic feet
3. Convert to cubic yards: 64 ÷ 27 = 2.37 cubic yards
4. Add 10% waste factor: 2.37 × 1.10 = 2.61 yd³
5. Round up for ordering: 3.0 cubic yards

That 10% waste factor covers spillage over forms, uneven subgrade that eats extra depth, and the reality that concrete trucks rarely deliver a perfectly clean load. Never order the exact calculated minimum - every experienced contractor rounds up.

Determining Yardage for Common Project Types

Driveways

Driveways are typically 5–6 inches thick and may have turned-down edges (thicker at the apron for vehicle load). For a standard 20×46 driveway at 5": Length × Width × Depth ÷ 27 = 20 × 46 × 0.417 ÷ 27 = 14.28 yd³ + 10% = 15.7 → round to 16 yd³.

Pro tip: Driveways with wire mesh or rebar need the forms set slightly thicker to accommodate reinforcement. That extra quarter-inch adds up - don't forget to account for it.

Footings

Foundation footings are measured in linear feet, not square feet. A footing that's 16" wide and 8" deep running 120 linear feet:

• Width: 16" = 1.33 ft
• Depth: 8" = 0.667 ft
• Volume: 120 × 1.33 × 0.667 ÷ 27 = 4.06 yd³ + 10% = 4.47 → round to 5 yd³

Concrete Columns and Sonotubes

Circular columns require the cylinder volume formula:
V = π × r² × h ÷ 27

For a 12" diameter sonotube that's 4 ft deep:
Radius = 0.5 ft, Height = 4 ft
V = 3.14159 × 0.5² × 4 ÷ 27 = 0.116 yd³ per column

If you're setting 12 columns: 0.116 × 12 = 1.39 yd³ → round to 2.0 yd³ (a single column's worth of extra is smart insurance).

Quick Reference: How Many Yards for Common Slab Sizes

Slab Size	4" Thick	5" Thick	6" Thick
10×10	1.23 yd³	1.54 yd³	1.85 yd³
12×12	1.78 yd³	2.22 yd³	2.67 yd³
20×20	4.94 yd³	6.17 yd³	7.41 yd³
24×24	7.11 yd³	8.89 yd³	10.67 yd³
30×30	11.11 yd³	13.89 yd³	16.67 yd³

Values include 10% waste factor and are rounded up to the nearest cubic yard. Always confirm with your supplier's minimum delivery requirements.

Common Mistakes When Determining Concrete Yardage

1. Forgetting the Waste Factor

Every project spills. Forms don't hold perfectly. The ground absorbs some. Order at least 5–10% extra, even on small jobs.

2. Measuring Depth at the Wrong Point

The deepest point of your excavated area is what matters, not the shallowest. If one corner is 3" and the opposite is 5", use 5" for your calculation.

3. Mixing Units

Feet, inches, and yards in the same formula equals disaster. Convert everything to feet first, then divide by 27 to get cubic yards. Every time.

4. Ignoring Short-Load Fees

Most ready-mix suppliers charge $150–$250 extra for orders under 5–8 cubic yards. If a truck can carry 10 yards and you only need 3, you're paying a short-load fee on the 7 empty yards of capacity. Sometimes ordering one extra yard and having leftover is cheaper than the short-load surcharge.

Bag Mix vs. Ready-Mix: When to Use Each

Knowing how to determine concrete yardage also helps you decide whether to use bags or order a truck:

• Under 2 cubic yards: Bags are usually more economical (a single truck has minimum charges of $300–$500)
• 2–8 cubic yards: Ready-mix is almost always cheaper per yard, but check short-load fees
• Over 8 cubic yards: Always order ready-mix - bag mix at this scale means mixing 200+ bags by hand

One 80-lb bag yields 0.60 cubic feet of cured concrete. That's 0.0222 cubic yards per bag. A 10×10 slab at 4" thick needs 34 bags. A 24×24 garage floor needs 278 bags. The math makes the decision obvious.

FAQ: Determining Concrete Yardage

How do I figure out concrete yardage for an irregular shape?

Break the area into rectangles, calculate each one separately, then add them together. For pie-shaped or L-shaped slabs, draw the outline on paper, split it at the corner, and calculate two rectangles instead.

Does rebar or wire mesh reduce the amount of concrete needed?

No. Reinforcement takes up negligible volume (less than 0.1%). Calculate your yardage based on form dimensions only.

What if my subgrade is uneven?

Increase your waste factor to 15% instead of 10%. Excavate to a consistent depth when possible, and always over-excavate in spots that are too high rather than under-filling low spots.

How much does one yard of concrete cost?

In 2026, ready-mix concrete runs $135–$175 per cubic yard nationally, varying by region. Short-load fees, fuel surcharges, and Saturday deliveries can add $100–$400+ to your total. See our 2026 pricing guide for a full regional breakdown.

Let the Calculator Do the Math

Knowing the formula is one thing. Getting the exact number in seconds - tailored to your project size, thickness, and region - is another. Our free concrete calculator handles all the conversions, waste factors, and regional pricing automatically so you can skip straight to ordering.

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