Estimate How Much Concrete A Slab Needs From Length, Width, Thickness And Quantity. The Main Result Is Shown In Cubic Metres With A Cubic Yard Equivalent, Plus Optional Waste Allowance, 20 Kg Bag Yield And Your Own A$/m³ Concrete Rate. Related Footing, Post And Multiple-Section Modes Are Included For Projects That Need More Than A Flat Slab.
Start With Slab Or Pad For A Standard Concrete Slab. Every Numeric Entry Displays Zero As A Placeholder Without Forcing A Leading Zero While You Type. Results Stay Hidden Until You Press Estimate Concrete Slab.
Your Result Will Appear Here After You Press Estimate Concrete Slab.
The PDF Includes The Slab Or Project Shape, Measurements, Cubic Metre Result, Cubic Yard Equivalent, Base Concrete Volume, Waste Allowance, 20 Kg Bag Estimate And Concrete-Only Cost.
A Concrete Slab Is A Three-Dimensional Volume. Multiply Length By Width By Slab Thickness After Converting Millimetres To Metres. The Estimator Adds Any Waste Allowance To The Base m³ Volume And Also Shows The Equivalent In Cubic Yards.
The Main Result Is Cubic Metres For Australian Concrete Planning, With The Cubic Yard Equivalent Included In The Result Description And PDF. Separate Figures Show Base Concrete, Waste, 20 Kg Bags And Concrete-Only Cost.
See The Geometric Slab Volume In Cubic Metres Before Waste Or Contingency Is Added.
Add A Percentage For Minor Measurement Differences, Spillage And Real Site Conditions.
Combine Base Slab Volume And Waste Into One Final m³ Planning Quantity, With A yd³ Equivalent For Comparison.
Estimate Whole Bags Using The Yield From The Exact Product You Plan To Buy.
Multiply The Final Cubic Metre Quantity By Your Own Local A$/m³ Ready-Mix Rate, While The Estimator Also Keeps The yd³ Equivalent Available.
Save The Main Measurements, yd³ Result, m³ Equivalent And Cost Estimate With The Site Name For Reference.
A Concrete Slab Estimate Starts With Three Measurements: Length, Width And Thickness. In Australia, Ready-Mix Concrete Is Normally Quoted And Ordered In Cubic Metres (m³), So This Estimator Uses Metric measurements as the main workflow and also provides a cubic yard equivalent. Enter slab length and width in metres, then enter slab thickness in millimetres.
The Most Reliable Slab Estimate Separates The Flat Slab From Any Thickened Edges, Beams, Footings Or Other Extra Concrete. A Simple Flat Slab Uses Length × Width × Thickness. If The Project Has Different depths or shapes, calculate those sections separately and add them before applying a practical waste allowance.
Concrete Volume (m³) = Length (m) × Width (m) × Depth (m)
If A Slab Is 6 m Long, 4 m Wide And 100 mm Deep, Convert 100 mm To 0.10 m. The Base Volume Is 6 × 4 × 0.10 = 2.40 m³.
Cubic Yards (yd³) = Cubic Metres (m³) × 1.30795
Using The Same Example, 2.40 m³ × 1.30795 = 3.14 yd³ Before Waste. If You Add A 10% Allowance, The Planning Volume Becomes 2.64 m³, Which Is About 3.45 yd³. For Australian Ready-Mix Orders, Confirm The Final m³ Quantity With Your Supplier Even When You Use Cubic Yards For Comparison Or Project Planning.
A Straight Strip Footing Uses The Same Basic Rectangular Formula. Add The Total Footing Length In Metres, Then Convert Width And Depth From Millimetres To Metres Before Multiplying.
Footing Volume = Total Length × Width × Depth
A Round Column Is A Cylinder. Divide The Diameter By Two To Find The Radius, Square The Radius, Multiply By π, Then Multiply By Height Or Depth. If You Have More Than One Identical Column, Multiply By The Quantity.
Volume = π × Radius² × Height
For Repeated Identical Sections, Calculate The Volume Of One Section Then Multiply By The Number Of Sections. If You Already Know The m³ Volume Per Section, The Multiple Sections Option Lets You Enter That Directly And Add A Small Known Extra Volume If Needed.
| Concrete Section | Example Measurements | Base Formula | Example Volume |
|---|---|---|---|
| Rectangular Slab | 6 m × 4 m × 100 mm | 6 × 4 × 0.10 | 2.40 m³ |
| Strip Footing | 20 m × 400 mm × 300 mm | 20 × 0.40 × 0.30 | 2.40 m³ |
| Round Column | 400 mm Diameter × 2 m | π × 0.20² × 2 | 0.25 m³ |
| 4 Identical Pads | 0.50 m³ Each | 0.50 × 4 | 2.00 m³ |
Many Concrete Drawings And Site Measurements Use Millimetres For Depth, Width Or Diameter. Before You Use A Cubic-Metre Formula, Convert Millimetres To Metres By Dividing By 1000.
| Millimetres | Metres | Common Use |
|---|---|---|
| 75 mm | 0.075 m | Thin Concrete Layer Example |
| 100 mm | 0.100 m | Common Calculation Example |
| 125 mm | 0.125 m | Thicker Slab Example |
| 150 mm | 0.150 m | Heavy Slab Example |
| 300 mm | 0.300 m | Footing Depth Example |
| 400 mm | 0.400 m | Footing Width Or Diameter Example |
Waste Or Contingency Is Added After The Base Geometric Volume Is Calculated. It Provides A Small Buffer For Minor Measurement Variation, Uneven Excavation, Form Movement, Spillage Or Other Real Site Conditions.
Final Quantity = Base Volume × (1 + Waste Percentage ÷ 100)
Bag Quantity Depends On The Finished Yield Of The Exact Product. A 20 Kg Bag Weight Does Not Automatically Equal One Fixed Concrete Volume. Enter The Manufacturer-Stated Yield Per Bag, Then Divide The Final Concrete Quantity By That Yield And Round Up To A Whole Bag.
20 Kg Bags = Final Concrete Quantity ÷ Yield Per Bag
For Larger Projects, Concrete Is Often Ordered In Cubic Metres From A Ready-Mix Supplier. Use The Calculator Result As A Planning Figure, Then Discuss The Final Order Quantity, mix specification, site access and delivery conditions with the supplier.
The Calculator Multiplies The Final Cubic Metre Volume By The A$/m³ Rate You Enter. The Same Result Is Also Converted To Cubic Yards For Unit Comparison And Planning. The Cost Is Concrete-Only And Does Not Automatically Include Delivery, Short-Load Charges, Pumping, Labour, Reinforcement, Formwork, Excavation, Finishing Or Other Project Costs.
A Project Can Have Several Different Concrete depths and shapes. A slab may be 100 mm deep, while a strip footing is 300 mm deep. A thickened edge may use extra concrete around the perimeter. Calculating these separately makes the final quantity easier to check.
This Tool Does Not Decide Concrete Strength, Slab Thickness, Reinforcement, Footing Size, Column Size, joint layout, exposure classification or structural requirements. Those decisions must come from the appropriate project specification, plans or professional advice.
Keeping Each Step Separate Makes It Easier To Check Slab Area, Thickness, m³ Volume, yd³ Equivalent And Waste Before You Order.
Measure The Finished Slab Length And Width Carefully.
Confirm Slab Thickness And Convert Millimetres To Metres.
Multiply Length × Width × Thickness For The Base m³ Volume.
Add A Practical Allowance And Review Final m³ And yd³.
These Slab Examples Show Cubic Metres And Approximate Cubic Yards Before And After Waste. Real slab thickness, edge details and site conditions can change the final order quantity.
| Project Example | Measurements | Base Volume | With 5% Waste | With 10% Waste |
|---|---|---|---|---|
| Small Pad | 2 m × 2 m × 100 mm | 0.40 m³ / 0.52 yd³ | 0.42 m³ / 0.55 yd³ | 0.44 m³ / 0.58 yd³ |
| Patio Slab | 5 m × 4 m × 100 mm | 2.00 m³ / 2.62 yd³ | 2.10 m³ / 2.75 yd³ | 2.20 m³ / 2.88 yd³ |
| Garage Slab | 6 m × 6 m × 100 mm | 3.60 m³ / 4.71 yd³ | 3.78 m³ / 4.94 yd³ | 3.96 m³ / 5.18 yd³ |
| Driveway Slab | 8 m × 3 m × 100 mm | 2.40 m³ / 3.14 yd³ | 2.52 m³ / 3.30 yd³ | 2.64 m³ / 3.45 yd³ |
| Workshop Slab | 8 m × 6 m × 125 mm | 6.00 m³ / 7.85 yd³ | 6.30 m³ / 8.24 yd³ | 6.60 m³ / 8.63 yd³ |
The Formula Is Straightforward, But Real Sites Can Use More Or Less Concrete Than A Perfect Geometric Shape.
Simple Answers About Slab Volume, Thickness, m³, yd³, waste allowance, 20 kg bags and concrete-only cost.
Multiply slab length by width by thickness in metres. For example, 100 mm thickness becomes 0.10 m. Add any separate thickened sections, then apply your waste allowance. The estimator shows m³ and the yd³ equivalent.
Cubic metres (m³) are the practical ordering unit for Australian ready-mix concrete. The estimator also shows cubic yards for comparison; 1 m³ is about 1.30795 yd³.
Divide By 1000. Therefore 100 mm = 0.10 m.
Yes. Calculate the flat slab first, then use the strip footing mode for a separate thickened edge or footing and combine the planned quantities.
Yes. Use the round mode with the slab diameter, thickness/depth and quantity. The estimator uses the cylinder volume formula.
There Is No Universal Percentage. The Appropriate Allowance Depends On Measurement Accuracy, excavation, formwork and site conditions.
Divide The Final Concrete Quantity By The Manufacturer-Stated Yield Per Bag And Round Up To A Whole Bag.
Each Numeric Field Is Empty But Displays A Zero Placeholder. This Keeps The Starting State Clear Without Forcing A Leading Zero When You Type A Number.
Yes. Enter Your Own A$/m³ Rate To Estimate Concrete Material Cost. Delivery, labour and other project costs are not automatically included.
The PDF Includes The Slab Or Project Shape, Measurements, m³ result, yd³ equivalent, base volume, waste allowance, 20 kg bag estimate and concrete-only cost.
Check Current Product Information, Supplier Advice And Australian Safety Guidance Before Ordering Or Carrying Out Concrete Work.
Australian Industry Information And Technical Resources For Concrete Construction.
Visit CCAANational Safety Information About Silica And Concrete-Related Work Hazards.
Read Silica GuidanceExample Australian Product Information For Packaged General Purpose Concrete.
View Product InformationConfirm Final m³ Quantity, Mix Requirements, Delivery Conditions And Supplier Fees Before Ordering.