Concrete Bags Calculator
Calculate how many bags of pre-mixed concrete you need. Enter volume to see bag counts for 20kg, 25kg, and 30kg sizes with waste factor included.
Part of the Concrete & Masonry calculators — see all tools in this category.
Current result
Volume of concrete needed in cubic meters
Typical: 10% for spillage and overfill
Leave blank to use default yields. Only override if your product has different specifications.
Default: 0.009 m³ (9 liters)
Default: 0.012 m³ (12 liters)
Default: 0.014 m³ (14 liters)
Enter bag prices to compare total costs for each size.
Price per 20kg bag
Price per 25kg bag
Price per 30kg bag
Results
Includes 10% waste factor
61.1 calculated, rounded up
45.8 calculated, rounded up
39.3 calculated, rounded up
Default yields: 20kg = 9L (0.009 m³), 25kg = 12L (0.012 m³), 30kg = 14L (0.014 m³). These are typical values for pre-mix concrete. Check your product packaging for exact specifications.
How it works and assumptions
Before estimating, read Calculating Concrete Shapes and Screed Bag Yields for measurement examples and the distinction between concrete, premixed screed and binder-only products.
This calculator helps you determine how many pre-mixed concrete bags to purchase for your project, showing counts for all three standard bag sizes.
- Enter the volume of concrete needed: Input the total volume in cubic meters (m³). If you have dimensions, use our Concrete Slab Calculator to find volume first.
- Adjust waste percentage: Default is 10% which accounts for spillage, mixing losses, and slight over-ordering. Increase for complex pours or inexperienced mixing.
- View bag counts for all sizes: See how many 20kg, 25kg, and 30kg bags you need. Compare to find the best option based on price and handling preference.
- Optional: Add custom yields: If your specific product has different yields than the defaults, enter them in the Advanced section for accurate calculations.
- Optional: Enter bag prices: Add price per bag for each size to see total cost estimates and find the most economical option.
Formula: Bags Needed = Volume (m³) × (1 + Waste%) ÷ Yield per Bag (m³)
Frequently Asked Questions
Sources and revision
Page revision: 2026-10-12