Concrete Calculator for Accurate Pour Estimates
Calculate concrete volume, material quantities, ready-mix loads, concrete bags, hand-mix materials, rebar, formwork and estimated project cost for slabs, footings, walls and columns.
Enter the dimensions of each concrete pour, choose the correct shape and measurement units, then add your waste, compaction and spillage allowances. The calculator converts the dimensions into cubic feet, cubic yards and cubic metres and calculates the concrete quantity required for ordering. For a slab or footing, enter length, width and thickness or depth; for a wall, enter length, height and thickness; for a round column, enter diameter and height; and for a square column, enter side length and height. You can then select bagged concrete, ready-mix concrete or a site-mixed concrete ratio to estimate bags, truck loads or cement, sand, aggregate and water.
How to Measure Your Concrete Project
Start by measuring every separate concrete section that will be poured. Measure length (L), width (W), thickness or depth (T/D), and height (H) using the units that match your project. The calculator supports feet (ft), inches (in), metres (m), centimetres (cm), yards (yd), millimetres (mm), and mixed dimension units where thickness requires a separate unit.
For rectangular concrete slabs and footings, the basic concrete volume comes from length × width × thickness. A wall uses length × height × thickness, while a round column uses the circular area from its diameter multiplied by height. A square column uses side × side × height. Enter the quantity when you have multiple identical pours, such as several footings or columns.
After the net concrete volume is calculated, the calculator can increase the order quantity using an over-order allowance, sub-base compaction allowance and spillage or pump-loss allowance. The final quantity helps estimate the amount of ready-mix concrete or bagged concrete to order, while optional cost inputs can calculate concrete material, delivery, pumping, placing and finishing, formwork and rebar costs.
Concrete Calculator
What are you pouring?
How is it supplied?
Reinforcement & finishing
OptionalCost estimate ($)
How the Concrete Calculator Works
Enter dimensions, choose the pour type, add allowances and select your concrete supply method.
The Concrete Calculator calculates the volume of each concrete pour from its dimensions, converts the result into cubic feet, cubic yards and cubic metres, and combines multiple pours into one project quantity. The calculator then applies over-order, sub-base compaction and spillage or pump-loss allowances to determine the concrete quantity to order.
Measure the Pour
Enter length, width, thickness, depth, diameter, side or height according to the selected concrete shape.
Choose Units
Use feet, inches, metres, centimetres or yards for dimensions and select the appropriate thickness unit.
Add Allowances
Include over-ordering, sub-base compaction and spillage or pump-loss percentages for a practical order quantity.
Review Materials
View concrete volume, bags, truck loads, hand-mix materials, rebar, formwork and optional project cost.
Concrete Calculator Formula
The calculation changes according to the shape of the concrete pour.
The core calculation is based on geometric volume. Dimensions are first converted into metres so the calculator can calculate cubic metres consistently, then the result is converted into cubic yards and cubic feet.
Use the same formula for rectangular slabs and footings, with footing thickness entered as depth.
Wall volume uses the wall run, vertical height and wall thickness.
The diameter determines the circular cross-sectional area of the column.
A square column uses its side dimension for both horizontal directions.
The total allowance combines the selected over-order percentage, sub-base compaction percentage and spillage or pump-loss percentage. For example, a 10% over-order allowance, 3% compaction allowance and 2% spillage allowance create a combined 15% allowance.
Concrete Calculator Example
Example: calculating the concrete required for a rectangular slab.
Consider a rectangular concrete slab measuring 20 ft long, 12 ft wide and 4 in thick. Enter the dimensions in the calculator, select Slab, choose feet for the main dimensions, choose inches for thickness, and set the over-order allowance to 10%.
Example Measurements
The net slab volume is approximately 2.96 yd³. With a 10% over-order allowance, the recommended order quantity is approximately 3.25 yd³ when calculated from the underlying metric volume.
The exact displayed result can vary with the selected allowance settings, unit selections and calculator inputs. For an actual order, confirm the calculated quantity with the concrete supplier because site conditions, access, formwork, grade changes and delivery requirements can affect the final amount.
Helpful Information Before Ordering Concrete
Use accurate measurements and match the calculator settings to your actual concrete supply method.
Measure Every Pour Separately
Separate slabs, footings, walls and columns can have different dimensions. Add another pour when the project contains different sections instead of averaging their measurements.
Check Thickness Carefully
Small changes in slab thickness can significantly change concrete volume. Enter the actual design thickness rather than estimating from the visible surface.
Use the Correct Shape
Select slab, footing, wall, round column or square column before entering dimensions because each shape uses a different volume formula.
Include Practical Allowances
The calculator lets you account for over-ordering, sub-base compaction and spillage or pump loss. The appropriate allowance depends on the project conditions and ordering method.
Match the Supply Method
Bagged concrete calculates the number of pre-mixed bags, ready-mix calculates truck loads and minimum charged volume, and site mixing estimates cement, sand, aggregate and water from the selected mix ratio.
Review Cost Inputs
Optional pricing can be entered per cubic yard, cubic metre, bag, square foot, square metre or square yard. Delivery, pump hire, placing and finishing, formwork and rebar can be included in the estimate.
Before You Use the Calculator
- Measure dimensions accurately: use a tape measure or project drawings and record each dimension in the correct unit.
- Convert inconsistent measurements: avoid mixing inches, feet, metres and centimetres without selecting the corresponding unit in the calculator.
- Separate different concrete sections: add individual pours when slabs, footings, walls or columns have different dimensions.
- Check concrete strength: choose the appropriate ready-mix strength or site-mix ratio for the intended structural or non-structural application.
- Consider access and delivery: ready-mix requirements can depend on truck capacity, minimum load charges, site access and delivery conditions.
- Allow for reinforcement: rebar quantities depend on the selected grid spacing, stocked bar length and the dimensions of the applicable slab or footing.
- Verify the final order: use the calculator as an estimate and confirm quantities, concrete mix specifications and site requirements with your supplier or engineer.
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Frequently Asked Questions
Answers to common questions about concrete volume, ordering and material estimates.