Concrete Calculator 2026 - Cubic Yards, Bags & Cost Estimator
Calculate concrete for any project - slabs, footings, columns, walls, and stairs. Get instant cubic yard volume, exact bag counts, rebar estimates aligned with ACI 318, and a full cost breakdown updated for 2026 USA prices. Works for DIY and professional contractors.
Key Concrete Facts for 2026
Concrete Weight
Per cubic foot (4,050 lbs/cu yd)
Ready-Mix Cost
Per cubic yard (2026 USA average)
Standard Slab Depth
Practical standard (IRC code min: 3.5 in)
Full Cure Time
100% design strength achieved
Who Uses This Concrete Calculator?
DIY Homeowners
Plan a concrete patio, backyard slab, or walkway without overspending on material. Get exact bag counts before heading to the hardware store.
Concrete Contractors
Generate fast, accurate material estimates for bids. Calculate cubic yards, rebar, and cost for driveways, foundations, and slabs in seconds.
Structural Engineers
Quickly verify volume calculations for footings, columns, and walls. Cross-check material quantities against spec sheets and design plans.
Landscapers
Estimate concrete for retaining walls, garden edging, steps, and decorative features. Calculate odd shapes including circles and trapezoids with ease.
🧮 Concrete Calculator
💰 Estimate Your Project Cost
Get accurate cost estimates before calling a contractor — compare prices and plan your budget.
Concrete Mix Ratio Chart
Standard mix ratios (cement:sand:aggregate) by application — footings, slabs, driveways, and structural work.
View Chart →How the Concrete Calculator Works
Select Your Project Shape
Choose from rectangle, circle, triangle, column, stairs, or curb and gutter. Each shape uses the correct volume formula for accurate results.
Enter Dimensions
Input length and width in feet and inches, and depth in inches. The calculator automatically converts everything to cubic yards - the standard unit for ordering concrete in the USA.
Set Your Options
Choose PSI strength, bag size, waste factor, and whether you need rebar, gravel base, and labor cost estimates. Defaults follow ACI 318 reinforcement guidance.
Get Instant Results
Receive cubic yards, bag count, rebar quantity, gravel volume, and full cost breakdown. Download a professional PDF report for your project records.
How to Calculate Concrete for Any Project
Calculating concrete starts with volume. Multiply length x width x depth (all in feet) to get cubic feet, then divide by 27 to convert to cubic yards (27 cubic feet = 1 cubic yard). For example, a 10 x 20 slab at 4 inches (0.333 ft) deep equals 66.67 cubic feet, or 2.47 cubic yards. Always add a 10% waste factor, giving you 2.72 cubic yards to order. Our full guide on how to calculate concrete walks through each step in detail.
Circles use the formula: pi x radius squared x depth. A 12-foot diameter circle pad at 4 inches deep requires about 1.40 cubic yards before waste. Columns use the same formula with height instead of depth. For complex projects like stairs, each step is calculated as a stacked rectangular volume from the ground up. The concrete formula calculation guide covers all shapes with worked examples.
Note on entering depth: length, width, height, and diameter fields accept feet and inches together (since projects often span multiple feet), but depth/thickness fields are inches-only, since slab and pad depth is almost always under 24 inches. If you want a 6-inch driveway, enter 6 in the depth field - not 6 feet.
Quick Reference: How Much Concrete Covers 1 Cubic Yard?
A fast way to sanity-check your order is the coverage-per-yard shortcut. One cubic yard of concrete covers less area as the pour gets thicker, since the same 27 cubic feet spreads over a smaller footprint.
| Slab Thickness | Coverage per Cubic Yard | Common Use |
|---|---|---|
| 3.5 in (code min.) | ~92.5 sq ft | IRC minimum slab-on-ground |
| 4 in | ~81 sq ft | Patios, sidewalks, standard slabs |
| 5 in | ~65 sq ft | Garage floors, light-duty driveways |
| 6 in | ~54 sq ft | Driveways, heavier vehicle loads |
Choosing the Right PSI Strength
PSI determines how strong your concrete is after curing (per ACI 301/318, normal-weight structural concrete starts at 2,500 PSI minimum). For most residential projects, 3,000 PSI handles patios, sidewalks, and light slabs. Driveways commonly use 4,000 PSI to handle vehicle weight and freeze-thaw cycles, though 3,500 PSI is an accepted minimum in milder climates. Use our concrete slab calculator for a dedicated slab estimator with PSI-based mix recommendations.
| PSI Rating | Best For | Typical Use | Cost Premium |
|---|---|---|---|
| 2,500 PSI | Sidewalks, paths | Light foot traffic only | Base price |
| 3,000 PSI | Patios, floors, walls | Standard residential | +$5/cu yd |
| 3,500 PSI | Pool decks, heavy slabs | Heavier residential | +$10/cu yd |
| 4,000 PSI | Driveways, garages | Vehicle traffic | +$15/cu yd |
| 4,500-5,000 PSI | Commercial, structural | Heavy loads, industrial | +$20-30/cu yd |
Slab Thickness: Code Minimum vs. Practical Standard
Under IRC 2024 Section R506.1, the legal minimum thickness for a residential slab-on-ground is 3.5 inches. In practice, most contractors pour 4 inches as the standard, since it offers more margin for load and cracking resistance at modest extra material cost. Driveways should be 4-6 inches depending on vehicle weight, and garage floors typically run 5-6 inches. Structural footings are sized separately by load and frost depth, not by the slab-thickness rule.
Footing Depth and Frost Line: Why "8-12 Inches" Isn't a National Answer
Footing depth is one of the most location-dependent numbers in residential construction. Per IRC Section R403.1.4, exterior footings must extend below the local frost line and at least 12 inches below grade - but the IRC does not publish one national frost depth; it's set locally per jurisdiction (IRC Table R301.2(1)). As a rough guide, frost depth ranges from near 0 inches in frost-free areas of Florida and southern Texas to 42-60+ inches across the northern tier (New England, the Upper Midwest, and mountain states). Always verify the exact requirement with your local building department before pouring footings or foundations - use our concrete footing calculator once you know your local frost depth.
Rebar Spacing and Cover (ACI 318)
ACI 318-19 Section 7.7.2.3 caps slab reinforcement spacing at the lesser of 3 times the slab thickness or 18 inches. That means a 4-inch slab should use roughly 12-inch spacing, not the wider 18-inch spacing that's only appropriate for slabs 6 inches or thicker. Concrete cover requirements also vary by exposure per ACI 318 Table 20.6.1.3: about 3 inches for footings cast against earth, 1.5 inches for weather-exposed bars size #5 and smaller, and as little as 0.75 inch for interior slabs not exposed to weather or ground contact. These are general guidelines - always confirm structural reinforcement requirements with a licensed engineer for load-bearing elements.
Ready-Mix vs. Bagged Concrete
Ready-mix is cost-effective for projects over roughly 1 cubic yard (about 45 bags at 80 lbs each). For a 10 x 10 slab at 4 inches, you need 1.23 cubic yards - that's 56 bags of 80 lb concrete or a small ready-mix order. Ready-mix runs approximately $125-$195 per cubic yard delivered in 2026, varying by region and supplier. Bagged concrete costs roughly $6-$8 per 80 lb bag at retail, making it noticeably more expensive per cubic yard than ready-mix once you're ordering enough for a full slab. Orders below a full truckload (typically 8-10 cubic yards) often carry a short-load fee of $50-$125. Use our concrete bag calculator to see the exact bag count and compare costs.
Typical Project Costs by Pour Size
These reference figures assume a standard 4-inch slab at 3,000-4,000 PSI, materials plus professional labor, based on 2026 USA averages. Actual costs vary by region, access, and finish requirements.
| Pour Size | Approx. Volume | Estimated Total Cost |
|---|---|---|
| 10 x 10 ft | ~1.35 cu yd (w/ waste) | $580-$1,150 |
| 12 x 12 ft | ~1.95 cu yd (w/ waste) | $830-$1,650 |
| 20 x 20 ft | ~5.4 cu yd (w/ waste) | $1,600-$3,200 |
💡 Pro Tip: Order 10% Extra
Always add at least 10% to your calculated volume. Subgrades are never perfectly level, forms bow slightly under pressure, and some concrete is lost during placement. Ready-mix is charged by the yard and is rarely refunded once mixed, so rounding up beats running short mid-pour.
⚠️ Safety First
Fresh concrete is highly alkaline and can cause chemical burns on contact with skin. Always wear gloves, safety glasses, and rubber boots when working with concrete. Avoid breathing concrete dust - use an N95 mask when mixing dry bags.
Real Construction Project Examples
🏠 20 x 20 Garage Slab
Dimensions: 20 ft x 20 ft x 6 in.
PSI: 4,000 (vehicles)
Rebar: #4 on 18 in. centers
Waste: 10%
📦 5.49 cubic yards of concrete
🔩 318 linear ft of rebar
💰 $2,300-$2,900 total estimated cost
At 6 inches thick for vehicle weight, this garage slab needs nearly double the concrete of a 4-inch patio. Use our slab calculator for detailed breakdowns.
🚗 Residential Driveway
Dimensions: 12 ft x 40 ft x 4 in.
PSI: 4,000
Rebar: #4 on 12 in. centers
Gravel base: 4 in.
📦 5.93 cubic yards with waste
🪨 1.97 cubic yards gravel base
💰 $3,100-$4,200 total estimated cost
A 12 x 40 ft driveway is one of the most common residential projects. Note the tighter 12-inch rebar spacing appropriate for a 4-inch slab per ACI 318. See the full breakdown with our concrete driveway calculator.
🏛️ 8 Deck Footings
Diameter: 12 in. (1 ft)
Depth: 48 in. (4 ft, verify against local frost line)
Quantity: 8 columns
PSI: 3,500
📦 1.03 cubic yards total
🛍️ 47 bags of 80 lb concrete
💰 $290-$380 materials only
8 small footings add up to just over 1 yard - a perfect bagged concrete project. Footing depth must clear your local frost line per IRC R403.1.4; 48 inches suits many mid-northern climates but always confirm locally. Use our column calculator for deck and pier footing estimates.
Concrete Calculator - Frequently Asked Questions
How many cubic yards of concrete do I need for a 10x10 slab?
A 10 x 10 slab at 4 inches thick needs 1.23 cubic yards before waste, or about 1.35 cubic yards with a 10% waste factor. At 6 inches thick, that becomes roughly 1.85 cubic yards with waste. Our concrete calculator above gives you the exact amount for any dimensions.
How do I convert cubic feet to cubic yards?
Divide cubic feet by 27. There are 27 cubic feet in one cubic yard (3 ft x 3 ft x 3 ft = 27 cu ft). For example, 67 cubic feet / 27 = 2.48 cubic yards. This calculator handles all conversions automatically. See our detailed concrete yardage calculator for more conversion options.
How many bags of concrete make a cubic yard?
One cubic yard requires approximately 45 bags of 80 lb concrete, 60 bags of 60 lb concrete, or 90 bags of 40 lb concrete, based on manufacturer-published yields (Quikrete: 0.60 / 0.45 / 0.30 cubic feet per bag respectively). For large projects over 1 cubic yard, ready-mix delivery is almost always cheaper than bags. Our concrete bag calculator shows an exact count with cost comparison.
What is the standard concrete slab thickness?
The IRC 2024 code minimum for a residential slab-on-ground is 3.5 inches, though 4 inches is the common practical standard. Driveways need 4-6 inches depending on vehicle weight. Garage floors should be 5-6 inches. Structural footings are sized by load and local frost depth, not the slab-thickness rule - always verify footing depth with your local building department.
How much does it cost to pour a concrete slab in 2026?
Concrete slab costs range from roughly $4 to $8 per square foot for a basic 4-inch slab in 2026, including materials and labor. A 12 x 12 patio costs approximately $830-$1,650. A 20 x 20 garage slab runs approximately $1,600-$3,200. Use our concrete cost calculator for a detailed cost breakdown by region.
Do I need rebar in a concrete slab?
Most residential slabs benefit from reinforcement. Per ACI 318, slab reinforcement spacing should not exceed the lesser of 3 times the slab thickness or 18 inches - for a standard 4-inch slab that works out to about 12-inch spacing, not 18. Thin slabs for patios and walkways can use wire mesh or #3 rebar; driveways and garage floors typically use #4 rebar. Any slab subject to vehicle loads, freeze-thaw cycles, or expansive soils benefits from reinforcement. Always check local building codes.
How long should I wait before walking on new concrete?
You can typically walk on concrete after 24-48 hours. Light vehicle traffic is generally safe after about 7 days when concrete reaches roughly 65-70% strength. Avoid full design loads until 28 days, when concrete reaches 100% of its design strength. Cold weather extends these timelines - below 50°F, curing slows significantly.
What is a short-load fee for concrete delivery?
Ready-mix trucks typically hold 8-10 cubic yards. Orders well under a full truckload commonly incur a short-load fee of $50-$125. For small projects, compare the total cost of bagged concrete versus a small ready-mix order plus delivery fee. Our calculator shows both options to help you decide.
Data Sources and Accuracy
- Concrete specifications: ACI 318-19 and ACI 301-20 (American Concrete Institute)
- Reinforcement spacing and cover: ACI 318-19 Section 7.7.2.3 and Table 20.6.1.3
- Building codes: IRC 2024 Sections R506.1 (slab thickness) and R403.1.4 (footing depth / frost line)
- Material costs: Industry-reported 2026 ready-mix pricing surveys, USA national averages
- Labor rates: Industry-reported 2026 residential concrete labor cost ranges
- Bag yields: Quikrete Technical Data Sheet (DS 1101) manufacturer specifications
- Curing timeline: ACI 308R curing guidance and Portland Cement Association reference data
📅 Last Updated:
Disclaimer: All results are estimates for planning purposes only. Pricing varies significantly by region, supplier, and order size. Footing depth and frost line requirements are set by your local jurisdiction, not a single national number - always verify with your local building department and a licensed engineer before finalizing structural elements.
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