Step 1: Select Your Shape and Units
Choose whether you are pouring a rectangular slab/footing or a round column. Toggle between Imperial (feet/inches) and Metric (meters/centimeters) at the top.
Step 2: Enter Dimensions
Enter the length, width, and depth for slabs, or diameter and height for columns. The 3D shape on the right will update instantly to reflect your dimensions.
Step 3: Choose Mix and Bag Size
Select your concrete mix ratio (1:2:4 is standard for most DIY projects). Choose the bag size you plan to buy so we can calculate exactly how many bags you need.
Step 4: Review and Download
Your results will appear instantly in the blue box. Click "Download PDF" to save a full report with all measurements, the 3D shape, and the formulas used.
Volume Formulas
Slab (Rectangle): Volume = Length × Width × Depth
Column (Round): Volume = π × (Diameter / 2)² × Height
Material Calculation (Dry Volume)
Concrete shrinks when mixed. We multiply the wet volume by 1.54 to get the dry volume required.
Cement: Dry Volume × (Cement Part / Total Parts) × Density (1440 kg/m³ or 90 lb/ft³)
Sand/Gravel: Dry Volume × (Respective Part / Total Parts)
Water: Cement Weight × 0.5 (Standard 0.5 Water-Cement Ratio)
Use this guide to select the right mix ratio for your project:
| Ratio | Strength | Best For |
|---|
| 1:1.5:3 | High (4000+ PSI) | Driveways, heavy loads, structural beams |
| 1:2:4 | Medium (3000 PSI) | Standard slabs, patios, walkways, foundations |
| 1:3:6 | Low (2000 PSI) | Mass concrete, leveling courses, non-structural |
| 1:5:10 | Very Low | Filler, large mass foundations, blinding concrete |
How much does a cubic yard of concrete weigh?
A typical cubic yard of solid concrete weighs about 4,050 lbs (2 tons). It's heavy! Ensure your subgrade is properly compacted.
Why do I need to add a waste factor?
Spillage, over-excavation, and uneven subgrades always consume more concrete than calculated. A 10% waste factor is standard industry practice to ensure you don't run short.
What is the difference between cement and concrete?
Cement is just the powdery binder (usually Portland cement). Concrete is the final mixture of cement, sand, gravel, and water. This calculator figures out how much cement (in bags) you need to make the total volume of concrete.
Can I use this for ready-mix concrete trucks?
Yes! Look at the "Total Volume" result in cubic yards (or cubic meters). You can order that exact amount from a ready-mix supplier. The bag calculations are specifically for DIY bagged concrete.