What is the Concrete Calculator?
Calculate the concrete needed for a slab in cubic yards, cubic meters and premix bags. Order the right amount the first time. These construction and DIY calculators estimate materials for common home projects and include sensible waste allowances.
How to use the Concrete Calculator
- Enter your length, your width, your thickness, your extra for waste.
- Results update automatically as you type; you can also press Calculate.
- Read the output: concrete needed, cubic meters, 80 lb bags, 60 lb bags.
- Use the 📊 chart to see the result visually, then copy or share it.
Formula and method
Worked example
With length = 10 ft, width = 10 ft, thickness = 4 in, extra for waste = 10 %, the Concrete Calculator returns concrete needed: 1.36 yd³; cubic meters: 1.038 m³; 80 lb bags: 62.
Tips for better results
- Add 5–15% for waste, cuts and breakage depending on the material.
- Measure twice and round up when buying — returns are easier than second trips.
- Coverage figures vary by product, so check the label or spec sheet.
⚠️ Material estimates are approximate. Follow local building codes and manufacturer instructions.
Frequently asked questions
What does the Concrete Calculator do?
Calculate the concrete needed for a slab in cubic yards, cubic meters and premix bags.
How is it calculated?
The Concrete Calculator uses this method: Volume = L × W × (T ÷ 12) ft³ ÷ 27 = yd³; 80 lb bag ≈ 0.60 ft³ · 60 lb ≈ 0.45 ft³.
Can you show an example?
With length = 10 ft, width = 10 ft, thickness = 4 in, extra for waste = 10 %, the Concrete Calculator returns concrete needed: 1.36 yd³; cubic meters: 1.038 m³; 80 lb bags: 62.
Is the Concrete Calculator accurate?
It uses standard published formulas and is tested against known values, but results are estimates for guidance. Material estimates are approximate. Follow local building codes and manufacturer instructions.
Is this tool free and private?
Yes — the Concrete Calculator is completely free with no sign-up, and it runs entirely in your browser, so the values you enter are never uploaded to our servers.
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