How do I calculate concrete volume?

Multiply length × width × thickness (all in the same unit). For a 3m × 2m slab that's 0.1m thick: 3 × 2 × 0.1 = 0.6 cubic meters of concrete needed.

How many bags of cement do I need per cubic meter?

For standard 1:2:4 mix, you need approximately 7 bags of 50kg cement per cubic meter of concrete. For richer mixes (1:1.5:3), use about 9 bags per cubic meter.

What is the 1:2:4 concrete mix ratio?

1:2:4 means 1 part cement, 2 parts sand, and 4 parts gravel by volume. This is a standard mix for general construction, suitable for foundations, slabs, and footings.

How thick should a concrete slab be?

Patio slabs: 10-15cm (4-6 inches). Driveway slabs: 15-20cm (6-8 inches). Garage floors: 15cm minimum. Structural floors: as per engineering specifications.

How do I calculate concrete for a circular column?

Use the formula: Volume = π × r² × height, where r is the radius. For a column 0.3m diameter and 3m tall: V = 3.14159 × 0.15² × 3 = 0.212m³

Should I order extra concrete?

Yes, always order 5-10% more than calculated to account for waste, spillage, uneven ground, and forms that may bulge. For complex shapes, order 10-15% extra.

What's the difference between concrete and cement?

Cement is just one ingredient - the binding agent. Concrete is the finished product made by mixing cement with sand, gravel (aggregates), and water. Cement typically makes up 10-15% of concrete volume.

How much water do I add to concrete?

Use a water-cement ratio of 0.4-0.5 by weight. For 50kg of cement, add 20-25 liters of water. Less water = stronger concrete, but harder to work with.

Concrete Calculator

Our concrete calculator helps contractors, builders, and DIY enthusiasts estimate the exact amount of concrete, cement, sand, and gravel needed for any project. Enter your dimensions, select your shape, and get instant material quantities with cost estimates. Supports both metric and imperial units.

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calendar_today Updated: April 2025

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New

Shape

Length

Width

Thickness

Waste Factor

Concrete Volume Needed

3.30 m³

Including 10% waste allowance

Materials (1:2:3 Mix)

Cement

16.5 bags

Sand

1.65 m³

Gravel

2.48 m³

Water

495 L

Total Weight

7.92

tonnes

Est. Cost

$495

@ $150/m³

Input Values

Shape

crop_square Slab / Footing

view_column Column (Square)

circle Column (Round)

stairs Stairs

Unit System

Metric (m)

Imperial (ft)

Length

Width

Thickness / Height

Quantity

auto_awesome AI Analysis

Enter your values and calculate to receive AI-powered insights about your results.

construction Mix Ratios (by volume)

Standard (1:2:3) ~3000 PSI

Strong (1:1.5:3) ~4000 PSI

High Strength 5000+ PSI

schedule Curing Time

⏱️ Initial set: 45-90 minutes
📅 70% strength: 7 days
✅ Full cure: 28 days

How to Use This Calculator

Select Shape

Choose the type of structure: slab, column, cylinder, or stairs

Choose Units

Select metric (meters) or imperial (feet) measurement system

Enter Dimensions

Input length, width, and thickness/height of your structure

Set Quantity

Enter the number of identical structures if building multiples

Review Materials

View the calculated volume and material quantities needed

The Formula

For standard concrete mix (1:2:4 ratio), you need approximately 7 bags of cement (50kg each), 0.42m³ sand, and 0.83m³ gravel per cubic meter of concrete.

Volume = Length × Width × Thickness

lightbulb Variables Explained

V Volume in cubic meters (m³) or cubic yards (yd³)
L Length of the area
W Width of the area
T Thickness/Depth of concrete

tips_and_updates Pro Tips

Order 5-10% extra concrete to account for waste and spillage

For structural concrete, use a 1:2:4 mix ratio (cement:sand:gravel)

Standard slab thickness: 10-15cm for patios, 15-20cm for driveways

Cure concrete for at least 7 days, keeping it moist

One 50kg bag of cement yields approximately 0.035m³ of concrete

Consider ready-mix concrete for volumes over 1m³ for better consistency

Calculate concrete volume by multiplying length × width × thickness. Convert to cubic meters or yards, then determine cement, sand, and gravel quantities based on your mix ratio.

Standard 1:2:4 mix is suitable for most projects. Use 1:1.5:3 for structural elements requiring extra strength. Lean mix 1:3:6 is for non-structural applications.