Estimate the concrete quantity and material price for a slab, patio, shed base, garage floor, path or other rectangular concrete area. Enter your own metric measurements, add a practical waste allowance, compare the quantity with 20 kg bag yield and enter a current local A$/m³ rate for a concrete-only budget.
Select the shape that best matches the pour. Every numeric field starts visually at 0, but the 0 is only a placeholder. When you type a number, it replaces the placeholder instead of being added after it.
Zero-entry behaviour: every faded 0 is only a placeholder. The actual field is empty, so typing a value never creates an unwanted leading zero.
Enter your slab dimensions and prices, then press Calculate Slab Price.
The total uses only the rates and allowances you enter. Supplier minimums, delivery, pumping, labour, excavation, reinforcement, formwork and finishing are not included unless you add them through the optional fields.
A rectangular concrete pour needs length, width and depth. Keep all three dimensions in metres before multiplying. When thickness is measured in millimetres, divide by 1000 first.
The tool separates the raw geometric volume from waste, bags and cost so you can see exactly which assumptions are changing the final planning quantity.
Calculate cubic metres for common residential and landscaping shapes.
Add your own contingency rather than relying on a fixed percentage.
Use the exact manufacturer yield in litres for bagged-concrete planning.
Enter your own current supplier quote instead of relying on a hard-coded price.
Save the estimate with measurements, waste, bags and concrete-only cost.
The visual zero is a placeholder only, so new typing replaces it automatically.
A reliable concrete estimate starts with volume, not with a guess about truck size or the number of bags. For a rectangular slab, patio, shed base or path, measure the finished internal length and width of the formed area, then multiply those dimensions by the concrete thickness. Because concrete thickness is commonly recorded in millimetres in Australia, convert the thickness to metres before multiplying. A 100 mm thickness is 0.10 m, 125 mm is 0.125 m and 150 mm is 0.15 m.
The Concrete Slab Price Estimator page is designed for planning quantities rather than structural design. It can tell you the mathematical volume created by your dimensions, but it cannot determine whether a slab should be 100 mm, 125 mm or another thickness. That decision can depend on the use of the slab, soil conditions, reinforcement, loads, engineering details, exposure, drainage, building classification and project approvals. Use the thickness and concrete specification shown on your approved plans, engineering documents or other project requirements where those documents apply.
m³ = Length (m) × Width (m) × Thickness (mm ÷ 1000)For example, if a formed area is 6 m long, 4 m wide and 100 mm thick, the mathematical volume is 6 × 4 × 0.10 = 2.40 m³ before any contingency. The useful part of a calculator is not simply doing that multiplication; it is keeping the base volume separate from any waste allowance so you can see exactly how much extra material is being added.
A generic example cannot account for your actual excavation, access, finished levels, ground conditions or formwork. A slab that looks rectangular on a sketch may contain steps, beams, rebates, thickenings, drainage falls or separate sections. A hand-dug footing can also be wider or deeper than its nominal dimension. Measure the real formed or excavated space as closely as practical before ordering concrete.
For irregular areas, divide the project into simple shapes. Calculate each rectangle or circular section separately and add the volumes. This is usually clearer than trying to force an irregular patio or driveway into one large rectangle. You can also use the Concrete Area Calculator first, then use this page to convert area and thickness into volume.
There is no single waste percentage that is correct for every concrete job. Accurate formwork over a level, well-prepared base may need only a modest contingency, while rough excavation, deep post holes, trenches, thickened edges or multiple small sections can make the required quantity less predictable. The calculator leaves the field at a visual 0 so you decide whether to add 3%, 5%, 10% or another value that reflects your site.
| Thickness | Depth In Metres | Concrete Per 10 m² | Concrete Per 50 m² |
|---|---|---|---|
| 75 mm | 0.075 m | 0.75 m³ | 3.75 m³ |
| 100 mm | 0.100 m | 1.00 m³ | 5.00 m³ |
| 125 mm | 0.125 m | 1.25 m³ | 6.25 m³ |
| 150 mm | 0.150 m | 1.50 m³ | 7.50 m³ |
| 200 mm | 0.200 m | 2.00 m³ | 10.00 m³ |
A circular concrete pad uses the area of a circle. Divide the diameter by two to get the radius, square the radius, multiply by π, then multiply by depth in metres. The calculator performs that calculation automatically. If you have multiple identical pads, enter the number of pads as the quantity. For a circular spa base, tank pad or landscape feature, check that a simple cylinder correctly represents the actual design before using the result as an order quantity.
Volume = π × Radius² × Depth × QuantityFor a straight strip footing, multiply total length by width and depth. The calculator accepts width and depth in millimetres because that is often convenient for site measurements. If the footing changes size along its length, calculate each section independently rather than averaging dimensions. Structural footing dimensions should come from the appropriate plans or engineering information; a volume calculator does not design a footing.
Fence posts, pergola posts and similar holes are commonly treated as cylinders for volume estimating. Enter the hole diameter, depth and number of holes. The optional displacement setting allows a rough reduction for the space occupied by the post itself. For a precise calculation, use the actual cross-sectional dimensions of the post rather than a generic percentage. Our Concrete Fence Post Calculator provides more dedicated post-hole planning.
Bagged concrete can be convenient for small repairs, individual post holes and locations where a concrete truck cannot practically reach the placement area. As volume increases, the bag count can become very large. Instead of assuming that every 20 kg bag makes the same volume, this calculator asks you to enter the manufacturer-stated mixed yield in litres. If a product states a yield of 10 litres, for example, one cubic metre would mathematically require 100 bags before waste because 1 m³ equals 1000 litres. Always use the current data sheet for the actual product you plan to buy.
For larger pours, compare bagged material with a current ready-mix quote. The calculator lets you enter both an A$/m³ ready-mix rate and an A$/bag price. Those figures are intentionally blank on load because product and delivery pricing can change by supplier, suburb, order size, access and service requirements. For another comparison, see the Concrete Bags Per Cubic Yard Calculator.
A concrete cost estimate is only meaningful when the price input matches the quote you are actually considering. A supply-only cubic-metre rate may not include delivery, small-load charges, waiting time, pumping, placement labour, reinforcement, formwork, excavation, base preparation, disposal, sealing or finishing. Enter the concrete rate quoted to you and treat the result as a concrete-material planning figure, not a full installed-project price.
For a broader budget, use the Total Concrete Cost Calculator or Concrete Cost Calculator alongside supplier and contractor quotes. Keep each cost category separate so you can compare quotes fairly.
A quantity estimate does not determine whether a project needs engineering, certification, permits, inspections or other approvals. Those requirements depend on the type of work, site, building classification and local rules. Use the applicable plans, specifications and advice from the relevant designer, engineer, builder, certifier or authority before concrete is placed.
The calculator should therefore be treated as a materials-planning tool. It can help you quantify a known design, but it should not be used to create the structural design itself.
Outdoor concrete should not be treated as a volume-only problem. Patios, paths and driveways often need controlled falls so water moves toward an appropriate drainage path rather than toward a building or neighbouring property. The correct slope depends on the design and surrounding levels. Use the Concrete Slope Calculator to translate rise and run into percent slope, ratio and angle, but confirm the required drainage design for the site.
An online estimate cannot assign the correct concrete strength, exposure classification, slump, aggregate size or durability requirements. Those choices depend on the project design, environment and applicable standards. Use the concrete specification shown on the relevant plans or obtain appropriate professional advice rather than selecting a mix only because it matches a volume result.
Concrete work can create hazards during mixing, placing, cutting, drilling, grinding and demolition. Concrete and other silica-containing materials can create hazardous dust when cut, drilled, ground or demolished. The safest work method is not determined by this calculator. Follow the current workplace-safety requirements that apply to your location, use appropriate controls and protective equipment, and use qualified trades where required.
| Example Project | Dimensions | Base Volume | Before Waste? |
|---|---|---|---|
| Small pad | 3 m × 3 m × 100 mm | 0.90 m³ | Yes |
| Patio area | 5 m × 4 m × 100 mm | 2.00 m³ | Yes |
| Path | 12 m × 1 m × 100 mm | 1.20 m³ | Yes |
| Thicker slab example | 6 m × 4 m × 125 mm | 3.00 m³ | Yes |
These examples illustrate the mathematics only. They are not recommendations for slab thickness or construction design. Use the required project thickness and specification for your job.
A useful concrete estimate should show more than one final dollar number. Keep the geometric volume, waste allowance, bag yield, ready-mix rate and bag price separate so you can change one assumption without rebuilding the whole calculation. This makes supplier comparisons easier and helps reveal whether a higher total is coming from extra volume, a higher material rate or a different bag yield.
For ready-mix, multiply the waste-adjusted cubic metres by the A$/m³ rate you enter. For bagged concrete, convert the adjusted volume to litres, divide by the mixed yield in litres per 20 kg bag and round up to whole bags. The calculator then multiplies the rounded bag count by your entered bag price. Neither result should be treated as a complete installed-project quote unless all other project costs are deliberately included elsewhere.
| Cost Category | Included Here? | What To Check |
|---|---|---|
| Concrete material | Yes, if you enter a rate | Current supplier A$/m³ or bag price |
| Delivery / short load | Not automatically | Supplier delivery rules and minimum order |
| Pump hire | No | Access, boom/line pump requirement and minimum hire |
| Reinforcement | No | Mesh, bars, chairs and project specification |
| Formwork | No | Timber, stakes, labour and stripping |
| Excavation / base | No | Earthworks, gravel, compaction and disposal |
| Labour / finishing | No | Placement, screeding, finishing, curing and sealing |
A slab price estimate begins with area and volume. Multiply slab length by slab width to get square metres. Convert thickness from millimetres to metres, then multiply area by thickness to get cubic metres. Apply the waste allowance to the volume, then multiply by the ready-mix rate you enter. Optional per-square-metre extras and fixed costs are added separately so you can see exactly what is changing the total.
Total = Adjusted m³ × A$/m³ + (Area × Extras A$/m²) + Fixed CostPrice per square metre can be useful when comparing slab options, but it should be derived from the actual slab design rather than treated as a universal rate. A thicker slab uses more concrete per square metre. Reinforcement, edge beams, excavation, base preparation, access, pumping and finish requirements can also move the installed cost substantially even when the surface area is unchanged.
| Slab Thickness | Concrete Per 1 m² | Concrete Per 10 m² | Concrete Per 100 m² |
|---|---|---|---|
| 75 mm | 0.075 m³ | 0.75 m³ | 7.50 m³ |
| 100 mm | 0.100 m³ | 1.00 m³ | 10.00 m³ |
| 125 mm | 0.125 m³ | 1.25 m³ | 12.50 m³ |
| 150 mm | 0.150 m³ | 1.50 m³ | 15.00 m³ |
The optional extras field is a convenient way to model slab costs that broadly scale with area. For example, you can enter a combined allowance for reinforcement, formwork, base preparation, labour or finishing if you already have a reliable A$/m² figure for those items. Keep in mind that some costs do not scale evenly with area, so the field is best treated as an estimating allowance rather than a substitute for itemised quotes.
Use the fixed-cost field for charges that do not naturally fit a square-metre rate, such as a pump minimum, delivery fee, small-load charge, site setup allowance or another known project-specific amount. If you do not want to include fixed costs, leave the field empty and the calculator will treat it as zero.
The estimator can show both ready-mix and bagged-concrete material pathways. The ready-mix total uses the A$/m³ rate you enter. The bagged total converts adjusted concrete volume into litres, divides by the verified mixed yield of one 20 kg bag, rounds up to whole bags, and multiplies by your bag price. This lets you see how the same slab geometry behaves under two purchasing methods without assuming that one method is automatically cheaper.
If you are building a larger estimate, combine this page with the Concrete Volume Calculator, Concrete Thickness Calculator, Concrete Coverage Calculator, Concrete Patio Calculator, Concrete Quantity Calculator and Concrete Foundation Calculator. Each tool focuses on a different part of the estimating process, so the underlying measurements should remain consistent between calculators.
Use the calculator result as one input in a broader site and ordering check.
Use the required dimensions, thickness, reinforcement and concrete specification from the appropriate project documents.
Check truck or pump access, placement route, washout arrangements and any supplier delivery requirements.
Check with the relevant certifier or authority whether approvals or inspections apply before concrete is placed.
Quick answers about volume, bags, waste, pricing and local project planning.
Calculate slab area, multiply by the required thickness to get cubic metres, add any chosen waste allowance, then multiply the adjusted volume by your concrete rate. Add reinforcement, formwork, labour, pumping or other costs separately if you want a fuller estimate.
A 100 mm slab uses 0.10 cubic metre of concrete per square metre of slab area before waste or thickened sections. For example, 50 m² at 100 mm thick equals 5.00 m³ before any allowance.
Not automatically. You can enter an optional A$/m² allowance and a fixed cost, but detailed reinforcement, excavation, formwork, pump and labour pricing should be itemised separately when accuracy matters.
Yes. Enter both a ready-mix A$/m³ rate and a 20 kg bag yield/price. The estimator will show the two material-cost pathways separately.
Multiply length in metres by width in metres by depth in metres. If the thickness is in millimetres, divide it by 1000 first.
The visible 0 is a placeholder only. The real field is empty, so when you type 5 you get 5 rather than 05. Reset returns the field to that empty placeholder state.
Only if you enter a waste percentage. The base volume and volume-with-waste are shown separately so you can see the effect of the allowance.
There is no universal percentage. The appropriate contingency depends on measurement accuracy, excavation, formwork, thickenings and site conditions. Re-measure before ordering.
Yes, if the patio can be represented by the available shapes and you know the required thickness. For more patio-specific inputs, use the Concrete Patio Calculator.
You can use it to estimate geometric concrete volume from known dimensions. It does not determine driveway thickness, reinforcement, crossover requirements, drainage or approvals.
Divide 1000 litres by the manufacturer-stated mixed yield per bag, then round up to whole bags. Different products can have different yields.
Only to the extent that the rate you enter includes delivery. Use the exact basis of your supplier quote and keep other costs separate.
No. Use the strength and specification required by the engineer, plans, builder, certifier or other applicable project documents.
Yes. Select Round Pad and enter diameter, depth and quantity.
Yes. Enter the total footing length, width and depth. The tool calculates volume only and does not design the footing.
Yes. Select Post Holes and enter hole diameter, depth and quantity. A dedicated fence-post calculator is also internally linked for more detailed planning.
Yes. Use the slab option when the pour can be represented by length, width and thickness. For irregular work, calculate separate simple sections and combine the volumes. The calculator estimates quantity only; it does not choose the structural thickness, reinforcement, drainage falls or concrete specification.
No. Approval, engineering and inspection requirements depend on the project and location. Check the applicable plans, certifier, engineer and local authority requirements separately.
Concrete and delivery costs can change by supplier, order size, location, access and service requirements. A current quote is more useful than a fixed online price.
No. It is a quantity and cost-planning tool only. Structural dimensions, reinforcement, strength, exposure requirements and approvals must come from the appropriate project information and professionals.
Use technical guidance, the project specification and current supplier information alongside any online concrete estimate.
Australian industry guides covering concrete construction, residential slabs, placing and related technical topics.
View CCAA Technical GuidesUse the dimensions, thickness, reinforcement, strength and detailing shown on the approved project documents where they apply.
Review The Estimating GuideConfirm current A$/m³ pricing, minimum loads, delivery fees, waiting time, access, pumping and order increments directly with the supplier.
Update Your Cost InputsCross-check volume, thickness, coverage, foundations, post holes and total concrete cost with related estimating tools.
Open Concrete Volume Calculator