How Many Yards of Concrete Do I Need? - Step-by-Step Calculator Guide | Concrete Yardage | Concrete Yardage
Published on 2026-05-30
How Many Yards of Concrete Do I Need?
Ordering the right amount of concrete is the single most important step in any pour project. Order too little and you get a weak cold joint where the second truck arrives; order too much and you pay for material that gets dumped on site. This guide walks you through the exact formula, worked examples for every common project type, and a free calculator that does the math for you.
The Concrete Yardage Formula
Concrete is sold and delivered in cubic yards. To find how many yards you need, calculate the volume of your slab in cubic feet and divide by 27 (because 1 cubic yard = 27 cubic feet).
Basic Formula
Yards = (Length ft × Width ft × Thickness ft) ÷ 27
Step-by-Step Example: 12×12 Patio at 4 Inches
- Convert thickness to feet: 4 inches ÷ 12 = 0.333 feet
- Calculate cubic feet: 12 ft × 12 ft × 0.333 ft = 47.96 cubic feet
- Convert to cubic yards: 47.96 ÷ 27 = 1.78 cubic yards
- Add 10% waste factor: 1.78 × 1.10 = 1.96 cubic yards
- Round up to order: 2.0 cubic yards
Always round up to the nearest quarter yard when ordering ready-mix. Suppliers typically sell in 0.25-yard increments.
Why You Need the 10% Waste Factor
Real-world pours are never perfectly level. Ground irregularities, spillage during discharge, over-excavation, and slight form bowing all increase the volume you actually use. Industry standard is 10% extra. Skipping it saves $15–$30 on a small pour but risks a $300+ cold joint repair if you run short.
When to Use a Larger Waste Factor
| Condition | Waste Factor | Why |
|---|---|---|
| Flat, compacted subgrade | 10% | Standard - most pours |
| Uneven or rocky ground | 15% | Void spaces below slab |
| Sloped terrain | 15–20% | Concrete flows to low spots, thickens at bottom |
| Stamped or decorative | 15% | Surface waste during stamping cleanup |
| Pumping with a line pump | 12% | Material left in the pump hose and hopper |
Yardage by Project Type (Common Sizes)
Here are the exact yardage calculations for the most frequently poured project dimensions. Use these as a quick reference, then verify with the calculator below.
| Project | Dimensions | Thickness | Cubic Yards | With 10% Waste |
|---|---|---|---|---|
| Small patio | 10×10 | 4 inches | 1.23 | 1.36 |
| Standard patio | 12×12 | 4 inches | 1.78 | 1.96 |
| Large patio | 16×16 | 5 inches | 3.95 | 4.35 |
| Sidewalk | 4×30 | 4 inches | 1.48 | 1.63 |
| Driveway (single) | 10×20 | 6 inches | 3.70 | 4.07 |
| Driveway (double) | 18×20 | 6 inches | 6.67 | 7.33 |
| Garage floor | 24×24 | 6 inches | 10.67 | 11.73 |
| Shed base | 10×12 | 4 inches | 1.48 | 1.63 |
| Hot tub pad | 8×8 | 6 inches | 1.19 | 1.31 |
Calculating Yardage for Non-Rectangular Shapes
Not every pour is a perfect rectangle. Here is how to handle the most common alternative shapes.
Round or Circular Slabs
Yards = (π × radius² × thickness) ÷ 27
Example: A 10-foot-diameter fire pit pad at 6 inches thick.
- Radius = 5 feet
- π × 5² × 0.5 = 3.14159 × 25 × 0.5 = 39.27 cubic feet
- 39.27 ÷ 27 = 1.45 cubic yards
- With 10% waste: 1.60 cubic yards
L-Shaped Slabs
Break the L into two rectangles. Calculate each separately, then add the volumes together.
Example: A 20×10 L-shaped patio where one leg is 10×6 and the other is 14×10 at 4 inches thick.
- Rectangle A: 10 × 6 × 0.333 = 19.98 cubic feet
- Rectangle B: 14 × 10 × 0.333 = 46.62 cubic feet
- Total: 66.60 cubic feet ÷ 27 = 2.47 cubic yards
- With 10% waste: 2.71 cubic yards
Footings and Trenches
Yards = (Length × width × depth) ÷ 27
Footings are long, narrow, and deeper than slabs. A typical house footing is 18 inches wide and 8 inches deep. For a 50-foot perimeter footing:
- 50 ft × 1.5 ft × 0.667 ft = 50.03 cubic feet
- 50.03 ÷ 27 = 1.85 cubic yards
Bag Count vs. Ready-Mix Delivery
Once you know your yardage, you face a key decision: mix bags yourself or order a ready-mix truck. The break-even point is roughly 1 cubic yard.
When to Use Bags
- Pours under 1 cubic yard (27 cubic feet or less)
- Remote sites where trucks cannot reach
- Small repair patches and setting fence posts
- Weekend warrior projects where you want to spread the work over two days
Bag Count Reference
| Cubic Yards Needed | 80-lb Bags | 60-lb Bags | Cost (80-lb @ $6.50) |
|---|---|---|---|
| 0.25 | 11 | 15 | $72 |
| 0.50 | 23 | 30 | $150 |
| 0.75 | 34 | 45 | $221 |
| 1.00 | 45 | 60 | $293 |
| 1.50 | 68 | 90 | $442 |
When to Order Ready-Mix
- Pours over 1 cubic yard - bags become exhausting and expensive
- Any project requiring a pump (trucks handle pump mixes)
- Time-sensitive pours where you need all concrete placed within 90 minutes
- 4,000+ PSI specifications that are hard to hit with bag mixes
Most ready-mix companies have a 1-yard minimum charge. Even if you only need 0.75 yards, you will pay for a full yard. Factor this into your bag-vs-truck decision.
2026 Cost Estimates by Region
Concrete pricing varies significantly by region due to aggregate availability, fuel costs, and demand. Here are current ready-mix prices per cubic yard (4,000 PSI, standard mix) as of mid-2026.
| Region | Price per yd³ | 1-yard min. charge | Delivery fee |
|---|---|---|---|
| Southeast (GA, FL, SC) | $135–$155 | $135 | $50–$80 |
| Northeast (NY, NJ, PA) | $175–$210 | $175 | $75–$120 |
| Midwest (OH, IL, MI) | $140–$165 | $140 | $50–$75 |
| Southwest (TX, AZ, NM) | $130–$150 | $130 | $40–$70 |
| West Coast (CA, OR, WA) | $185–$225 | $185 | $80–$130 |
| Mountain (CO, UT, MT) | $155–$180 | $155 | $60–$90 |
Concrete Yardage Checklist Before You Order
Use this checklist to make sure your order is right the first time.
- Measure twice: Verify length, width, and thickness with a tape measure - do not estimate from the plan.
- Account for reinforcement displacement: Rebar and mesh displace a small amount of concrete - typically negligible for flatwork, but add 3–5% for heavily reinforced mats.
- Confirm subgrade prep: Compacted gravel base must be level before you measure. If the ground is uneven, your thickness varies and you will use more concrete than calculated.
- Call the plant: Confirm mix design, PSI rating, and any additives (air entrainment for freeze-thaw, accelerator for cold weather). These affect yield slightly.
- Schedule delivery: Book 3–5 business days ahead in normal season; 1–2 weeks in spring/summer peak.
- Have a washout plan: The truck needs a designated washout area on site - typically a hole lined with plastic or a wheelbarrow for small pours.
Common Mistakes That Waste Concrete (and Money)
- Measuring in inches, forgetting to convert to feet: If you plug 4 (inches) instead of 0.333 (feet) for thickness, your volume is 12× too high. This is the number-one ordering mistake.
- Ignoring subgrade settlement: If the ground under your forms settles after you measure, your slab ends up thicker in those spots - and you need more concrete than you calculated.
- Using nominal thickness for footings: A "6-inch" footing often ends up 7–8 inches after excavation irregularities. Measure the actual excavated depth.
- Forgetting steps and thickened edges: A patio with a 12-inch-thick edge beam uses significantly more concrete than one with a uniform 4-inch thickness. Calculate edge beams separately.
- Not accounting for pump waste: Pumping leaves 0.25–0.5 cubic yards in the hose and hopper. Add this to your order.
Try Our Free Concrete Yardage Calculator
Why do the math by hand when our calculator handles it instantly? Enter your length, width, and thickness to get cubic yards, bag counts, and a cost estimate - all in one click.
Try the free concrete calculator at concreteyardage.com →
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Frequently Asked Questions
How many yards of concrete for a 10×10 slab at 4 inches?
1.23 cubic yards. With the 10% waste factor, order 1.36 yards - round up to 1.5 yards from your supplier.
What is the minimum order from a ready-mix company?
Most companies have a 1-yard minimum. Some short-load deliveries allow 0.5 yards but charge a premium ($25–$50 extra). Under 0.75 yards, bag mixes are usually cheaper.
How many 80-lb bags make 1 cubic yard?
45 bags. Each 80-lb bag yields approximately 0.60 cubic feet of concrete. At $6.50 per bag, 1 yard from bags costs about $293 - significantly more than ready-mix at $135–$185 per yard.
How thick should a concrete driveway be?
6 inches is the standard for residential driveways supporting passenger vehicles. For heavy trucks or RVs, use 8 inches with #4 rebar at 16-inch centers. Never pour a driveway at 4 inches - it will crack under vehicle weight within 1–2 years.
How far in advance should I schedule a concrete delivery?
3–5 business days for standard mixes in off-peak season. During the busy spring and summer months (April through August), book 1–2 weeks ahead. Colored or stamped concrete may need 2–3 weeks lead time for custom batching.
Can I pour half the order today and half tomorrow?
Not recommended. The joint between the two pours is a cold joint - a natural crack line. If you must pour in stages, install a proper construction joint with keyway and dowels, and plan the joint location at a control line. For most residential slabs, pour the entire batch in one continuous operation.