Concrete Yardage Calculator
Calculate exact cubic yard displacement, ready-mix truckload fractions, and 80lb/60lb premix bag counts with subgrade overpour margins.
How to Figure Concrete Yardage
Concrete is ordered by the cubic yard, so every estimate starts with volume. To figure concrete yardage, measure length and width in feet and thickness in inches, then divide by the right constant. The calculator above does this instantly and adds a waste margin, bag counts, and truck loads. The sections below give the formulas, show how to convert square footage to yards of concrete, list bag yields, and cover what a yard typically costs so you can determine exactly how much to order.
The Standard Formulas for Concrete Yardage
The core concrete yardage formula is length times width times thickness in feet, divided by 27. Use the field version to compute yardage straight from square footage, and the column formula for round footings and sonotubes.
Cubic Yards = (Length (ft) × Width (ft) × (Thickness (in) / 12)) / 27
Cubic Yards = Square Footage / 81
Dividing square footage by 324 yields cubic yards per inch of depth; for a 4-inch pour: 324 / 4 = 81 sq ft/yd³.
Cubic Yards = (π × (Radius in inches / 12)² × Depth in feet) / 27
10% Subgrade Allowance Clause: Always include a 10% overpour margin to account for sub-base unevenness, grade deflection, and trench spillage.
Square Footage Coverage per 1 Cubic Yard
To convert square footage to yards of concrete, divide your total square feet by the coverage figure for your slab thickness. At 4 inches one cubic yard covers 81 square feet, so a 400 square foot patio needs about 5 cubic yards before waste.
| Thickness | Coverage | Typical Application |
|---|---|---|
| 2 inches (50 mm) | 162 sq ft | Non-structural resurfacing / mud slabs |
| 3 inches (75 mm) | 108 sq ft | Sidewalks, lightweight equipment pads |
| 4 inches (100 mm) | 81 sq ft | Standard residential patios, walkways, garage floors |
| 5 inches (125 mm) | 65 sq ft | Light-duty residential driveways |
| 6 inches (150 mm) | 54 sq ft | Heavy-duty driveways, commercial slabs, RV parking |
| 8 inches (200 mm) | 40.5 sq ft | Structural footings, industrial equipment pads |
Bagged Premix Sacking Matrix
1 Cubic Yard = 27 Cubic Feet = 46,656 Cubic Inches (~4,050 lbs wet weight).
- 80-lb Concrete Sack: Yields 0.60 cu ft (0.0222 yd³). Takes 45 bags to pour 1 cubic yard.
- 60-lb Concrete Sack: Yields 0.45 cu ft (0.0167 yd³). Takes 60 bags to pour 1 cubic yard.
- 50-lb Concrete Sack: Yields 0.375 cu ft (0.0139 yd³). Takes 72 bags to pour 1 cubic yard.
Ready-Mix Dispatch Specifications
Compressive Strength
- 3,000 PSI: Non-reinforced footings, pathways, residential deck piers.
- 4,000 PSI: Standard driveways, garage slabs, vehicle parking (freeze/thaw durable).
- 5,000 PSI: Heavy equipment pads, commercial loading docks, harsh chemical exposure.
Logistics & Tolerances
- Standard Drum Capacity: Standard tandem-axle transit mixers transport 9.0 to 10.0 cubic yards. Tri-axle units handle up to 11.0 yards.
- Slump Tolerances (ASTM C143): 4 inches (± 1 inch) for standard flatwork chute pours; 5 to 6 inches for pumped lines.
What a Cubic Yard of Concrete Costs
Delivered ready mix runs roughly $130 to $170 per cubic yard across most of the country, before delivery and add ons. The price moves with mix strength, distance from the plant, and fuel, so treat this as a planning range and confirm it with a local quote.
- Short load fees: Orders under about 3 to 4 cubic yards usually carry a flat fee, often $50 to $150, because the truck leaves partly full.
- Bags vs truck: Bagged mix costs more per yard once you pass a yard or so. Under one yard, bags avoid the short load fee. Past 1.5 to 2 yards, a delivered truck wins on both price and labor.
- Add ons: A concrete pump, weekend or winter mix, and long chute or wait time are billed on top of the yard price.
Multiply the total yards from the calculator by your local price per yard to estimate concrete yardage cost, then keep the waste margin so you are not paying a second short load fee for a small top up truck.
Jobsite Dispatch FAQ
Multiply the slab length by width in feet, multiply by thickness in feet (inches divided by 12), then divide the total cubic feet by 27. Add 10% to cover form flexing and excavation grade variations.
One cubic yard covers exactly 81 square feet at a 4-inch depth (or 108 sq ft at 3 inches, and 54 sq ft at 6 inches).
It takes 45 bags of 80 lb ready-mix concrete to make one full cubic yard (27 cu ft).
For jobs under 1 cubic yard (fewer than 45 bags), purchasing bagged mix is typically cheaper and avoids short-load truck fees. For pours of 1.5 cubic yards or greater, delivered ready-mix is more economical, ensures uniform compressive strength, and eliminates significant manual labor.
Standard cured normal-weight concrete weighs approximately 4,000 to 4,050 lbs per cubic yard (145–150 lbs/cu ft).
Delivered ready mix typically runs about $130 to $170 per cubic yard before delivery and add ons, and the price varies by region, mix strength, and distance from the plant. Orders under 3 to 4 yards usually add a short load fee of around $50 to $150. Confirm the number with a local supplier quote.