About this tool Calculate material quantities for common BS 8500 designated and prescribed concrete mixes. Select from 8 mixes — GEN 0 through RC 50 plus PAC 1 — and enter the volume required to get cement, sand, coarse aggregate, and water quantities.
Results include both net quantities and order quantities with a 10% waste allowance. Cement is shown in kilograms and as 25kg bag counts — the figure you need when ordering bagged cement for site-mixed concrete.
The mix proportions reference table shows all 8 mixes side by side, making it easy to compare material requirements across different strength grades.
How to use this tool 1. Select the mix designation — choose based on the required strength class and application (shown below each mix).
2. Enter the volume — in m³. Use the Concrete Volume Calculator if you need to work this out from dimensions.
3. Read the results — use the order quantities (including 10% waste) for procurement. Cement bag count rounds up to whole bags.
Technical information Mix proportions are typical for 20mm maximum aggregate size with medium workability (slump class S2/S3). Based on BS 8500-2 designated mix guidance.
Strength classes follow the BS EN 206 / BS 8500 notation: C20/25 means 20 N/mm² cylinder strength / 25 N/mm² cube strength.
Water/cement ratios decrease with increasing strength grade — from ~1.0 for GEN 0 to ~0.36 for RC 50.
Limitations Mix proportions are typical industry values for guidance. Actual batch quantities depend on aggregate grading, moisture content, cement type, and required workability. Always confirm with your supplier or batch plant for production mixes.
This tool is for site-batched or small-quantity estimation. Ready-mix concrete is specified by strength class and consistency, not by constituent weights — your supplier designs the mix.
Designated mixes (GEN, RC, PAC) have specific durability requirements per BS 8500-1 Table A.3. Ensure the selected mix meets the exposure class for your application.
Revision history 12 May 2026: Initial release
Disclaimer This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.
Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.
All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.
By using this tool, you accept full responsibility for how you interpret and apply the information provided.
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