Concrete Calculators

Estimate concrete volume, bags, slabs, footings, and costs. Built for tradies who need fast, accurate concrete estimates for quotes and ordering.

Concrete Tools

Which Calculator Should I Use?

I want to… Use this calculator
Calculate cubic meters for a slab, footing, or post hole Concrete Volume Calculator
Calculate volume for a specific slab size Concrete Slab Calculator
Calculate volume for footings or foundations Concrete Footing Calculator
Estimate concrete for a full build Builder Concrete Volume Calculator
Estimate concrete for a driveway Driveway Concrete Volume Calculator

Who These Concrete Tools Are For

  • Concrete Contractors — calculate exact volume for slabs, footings, and driveways
  • Builders & Excavators — estimate concrete for foundations and retaining walls
  • Landscapers — calculate concrete for paths, patios, and steps
  • DIY Homeowners — know how many bags or how many cubic meters to order

How to Use These Calculators for a Real Job

  1. Start with the Concrete Volume Calculator to calculate cubic meters for your slab, footing, or post hole.
  2. Choose between ready-mix (cubic meters) or bagged concrete depending on job size.
  3. Add 5–10% waste for spillage, uneven ground, and formwork variations.
  4. Use the Driveway Concrete Calculator to estimate total cost including concrete, delivery, and pump hire.

💡 Pro Tips from Tradies

  • Always order 5–10% extra — concrete suppliers charge more for a top-up than it costs to order extra upfront. Running short mid-pour is a disaster.
  • Know your access — if the truck can’t reach the pour site, factor in pump hire ($400–$800) or wheelbarrow labour time.
  • Check slump before pouring — too wet and it weakens the concrete, too dry and it won’t flow. Most slabs need 80–100mm slump.
  • Time your order — concrete starts setting in 60–90 minutes. Have all labour and tools ready before the truck arrives.
  • Add reinforcement — mesh, rebar, or fibre reinforcement adds cost but prevents cracking. Factor this into your quote.

Concrete Job-Specific Quick Tips

🏠 Slabs & Driveways

  • Minimum thickness: 100mm for domestic slabs, 120mm for driveways
  • Add reinforcement mesh or rebar for strength
  • Install expansion joints every 4–5m to prevent cracking
  • Slope 1–2% for drainage

🕳️ Post Holes & Footings

  • Hole should be 3x the post width and 1/3 of post length in ground
  • Add 100–150mm of gravel at the bottom for drainage
  • Use post brackets for decks to keep timber off concrete
  • Calculate each hole individually — depths vary

🧱 Retaining Walls & Foundations

  • Footing depth should be below frost line in cold climates
  • Width should be 2x wall thickness minimum
  • Add reinforcing steel for structural walls
  • Engineered drawings may specify exact mix and reinforcement

🧺 Small Jobs & DIY

  • Use bagged concrete for post holes, small paths, and repairs
  • One 20kg bag covers roughly 0.01m³
  • Mix small batches in a wheelbarrow or hire a small mixer
  • Always add water slowly — you can add more but can’t remove it

Common Concrete Calculation Questions

How do I calculate concrete volume for a slab?

Multiply length × width × thickness (in meters) to get cubic meters. Example: a 5m × 4m slab at 0.1m thick = 2 cubic meters. Use the Concrete Volume Calculator to do this automatically.

How much waste should I add for concrete?

Add 5–10% waste for slabs and footings. For post holes and tricky pours, add 10–15%. It’s cheaper to order extra than to pay for a truck to come back with a top-up.

How much does concrete cost per cubic meter?

Ready-mix concrete typically costs $200–$300 per cubic meter depending on your location, strength grade, and quantity. Add delivery fees ($100–$300) and pump hire ($400–$800) if needed.

What strength concrete do I need?

  • 20 MPa (standard): Driveways, paths, shed slabs
  • 25 MPa: House slabs, footings, retaining walls
  • 32 MPa: Commercial slabs, heavy traffic areas
  • 40+ MPa: Structural columns, bridges, high-strength applications

How long does concrete take to cure?

Concrete reaches 70% strength in 7 days and full strength in 28 days. No heavy traffic for 7 days, and keep it damp to prevent cracking. Factor curing time into your job schedule.

Why Getting Concrete Quantities Right Matters

Concrete is expensive and unforgiving. Under-order and you’re paying for a top-up truck (plus delays). Over-order and you’re paying for concrete you can’t use. Accurate estimates help you:

  • Avoid costly top-up deliveries and job delays
  • Quote accurately and maintain profit margins
  • Order confidently from concrete suppliers
  • Minimise waste and environmental impact