CONSTRUCTION CALCULATOR
Concrete Calculator
Estimate how much concrete you need in cubic yards or cubic meters for slabs, pads, rectangular footings and post holes. Combine multiple pours, compare ready-mix with 40 lb, 60 lb and 80 lb bags, add an ordering allowance and estimate material cost before you buy.
SLAB / PAD
Project measurements
Calculate using
Use slab mode when you know the length, width and thickness of a rectangular pour.
LIVE PREVIEWSlab / pad
Calculated10 ft × 10 ft4 in thick · 1 item
Illustrative geometry only — use the entered dimensions for ordering.ORDER VOLUME
—yd³
Concrete including the selected extra-material allowance.
Base volume—yd³ before extra
Extra volume—yd³ allowance
Metric volume—m³ to order
Project area—ft²
MULTIPLE POURS
Build one combined concrete order.
Add the current calculation to a temporary project list, then mix slabs, footings, post holes, known areas and known volumes into one combined total. The selected extra percentage is applied once to the combined base volume.
No pours added yet. Calculate a slab, footing, post-hole group or known quantity above, then add it here.
Pour items0combined calculations
Base concrete—yd³ before extra
Project order total—yd³ including extra
PURCHASE PLANNING
Ready-mix or bagged concrete?
Turn either the current calculation or your combined project total into a purchase quantity. Use ready-mix for a volume-based quote or compare standard 40 lb, 60 lb and 80 lb bags for smaller jobs.
Purchase plan uses
Enter a supplier price only if you have one. Unit switching converts the price basis so the estimated total stays the same.
Bag counts always round up to whole bags. Yield values are planning estimates; confirm the product label before buying.
PURCHASE QUANTITY—Ready-mix concrete
Estimated material costAdd a priceOptional supplier pricing
BAG ALTERNATIVES
Includes the selected extra-material allowance.Equivalent whole-bag quantities
PROJECT OUTPUT
Concrete order summary.
A compact view of the calculation currently feeding Purchase Planning. Copy it to your notes or print the clean summary to save it as a PDF for a supplier quote or project record.
ScopeCurrent calculationSlab
Base concrete—yd³ before extra
Order concrete—yd³ including extra
Allowance10%applied once to the base volume
POUR BREAKDOWN
Current calculation
SHOPPING OUTPUT
What to ask for
Ready-mix concrete—Current calculation
Estimated material costAdd a priceOptional supplier pricing
Whole-bag reference—40 lb · 60 lb · 80 lb alternatives
Planning estimate only. Confirm mix specification, minimum delivery, short-load fees, bag yield and supplier requirements before ordering.
CALCULATION METHOD
How to calculate concrete volume and order quantity
MetricSketch converts the geometry you know into a base concrete volume, then applies the selected extra-material allowance to produce an order quantity. Slab and footing modes use rectangular volume, post-hole mode uses cylindrical volume, and known-area or known-volume modes let you start further along the calculation.
Base volume = Length × Width × Thickness
Order volume = Base volume × (1 + Extra %)
Order volume = Base volume × (1 + Extra %)
- Choose the project shape.Use Slab, Footing, Post holes, Known area or Known volume depending on the measurements you already have.
- Calculate the base concrete volume.The calculator converts the entered geometry into cubic yards and cubic meters.
- Add an ordering allowance.Extra material is applied on top of the base volume so the order quantity can include your chosen margin.
- Combine multiple pours when needed.Add slabs, footings, post-hole groups or known quantities to one temporary project total.
- Plan the purchase.Compare ready-mix volume with whole 40 lb, 60 lb and 80 lb bag counts, then add supplier pricing when available.
FIVE INPUT PATHS
Calculate slabs, footings, post holes, areas or known volume.
Rectangular slabs, pads and patios. Quantity can represent several identical pours.
Continuous or repeated rectangular footings using length, width, depth and quantity.
Cylindrical holes using diameter, depth and number of holes.
Square footage or square meters plus the concrete thickness.
A cubic-yard or cubic-meter figure that only needs an ordering allowance.
WORKED EXAMPLE
Example: a 10 ft × 10 ft concrete slab
A slab measuring 10 ft by 10 ft at 4 in thick has a base volume of about 1.23 yd³. With a 10% extra-material allowance, the order quantity becomes about 1.36 yd³. Use the purchase planner above to compare that volume with ready-mix pricing or whole-bag alternatives.
Concrete ordering requirements vary by supplier. Confirm minimum loads, short-load fees, mix specification and actual bag yield before purchasing.
CONCRETE CALCULATOR FAQ
Common questions before ordering concrete
These answers explain the quantities shown by the calculator and when supplier information should replace a planning assumption.
How do I calculate how much concrete I need?
Calculate the volume of the pour from its dimensions, then convert that volume into cubic yards or cubic meters. MetricSketch handles the conversions and can add an extra-material percentage to the base quantity.
How many cubic yards of concrete are in a slab?
For a rectangular slab, multiply length by width by thickness and convert the result to cubic yards. In US units, thickness is commonly entered in inches while length and width are entered in feet.
How many bags of concrete do I need?
Bag count depends on the concrete volume required and the yield of the bag size. The purchase planner compares whole 40 lb, 60 lb and 80 lb bag counts using planning yields; always confirm the actual product label before buying.
Can I calculate concrete for footings and post holes?
Yes. Footing mode uses rectangular length, width and depth, while post-hole mode uses hole diameter, depth and quantity for cylindrical pours.
How much extra concrete should I order?
The correct allowance depends on the project, formwork, excavation accuracy and supplier requirements. MetricSketch lets you choose the percentage instead of applying a fixed recommendation.
Should I use ready-mix concrete or bags?
Ready-mix is ordered by volume, while bagged concrete is purchased in whole bags. The calculator shows both approaches so you can compare quantities and optional supplier prices for your project.