What is the standard concrete mix ratio in the UK?

The most common general-purpose mix is 1:2:3 (one part cement, two parts sharp sand, three parts aggregate). This is suitable for foundations, paths, and most domestic concrete work. For structural elements, a stronger 1:1.5:2.5 mix is used. All ratios are by volume.

How many bags of cement do I need per m³ of concrete?

For a standard general-purpose 1:2:3 mix, you need approximately 6-7 bags (25kg) of cement per cubic metre of concrete. A stronger 1:1.5:2.5 mix requires around 8 bags per m³. The exact amount varies slightly depending on aggregate size and moisture content.

What type of sand do I use for concrete?

Use sharp sand (also called concreting sand or grit sand) for making concrete — not building sand. Sharp sand has coarser, angular particles that interlock and give concrete its strength. Building sand (soft sand) is finer and is used for mortar and rendering, not concrete.

What size aggregate should I use?

For most domestic concrete work, 20mm gravel aggregate is standard. Use 10mm aggregate for thinner sections (under 75mm) or where you need a smoother finish. Both are widely available from UK builders merchants as 'all-in ballast' or separately graded.

Is it cheaper to mix concrete myself or order ready-mix?

For small jobs (under 1m³), site-mixing is usually cheaper. For larger pours (over 2m³), ready-mix is often more cost-effective when you factor in labour time, mixer hire, and material waste. Ready-mix also gives a more consistent quality. The crossover point is typically around 1-2 m³.

Concrete Mix Calculator — Cement, Sand & Aggregate Ratios UK

How We Calculate This

This calculator works by multiplying your required concrete volume by the material quantities for your chosen mix ratio. The rates are based on standard UK concrete mix designs used across the construction industry.

Mix ratios explained

General purpose (1:2:3): 1 part cement, 2 parts sharp sand, 3 parts coarse aggregate. ~7 bags cement, 0.5t sand, 0.8t aggregate per m³.
Strong mix (1:1.5:2.5): Higher cement content for structural work. ~8 bags cement, 0.45t sand, 0.7t aggregate per m³.
Weak mix (1:3:6): Lower cement for blinding and non-structural fill. ~4 bags cement, 0.6t sand, 0.9t aggregate per m³.
Paving/post mix (1:2:4): Good all-rounder for fence posts and paving. ~6 bags cement, 0.5t sand, 0.75t aggregate per m³.

Standards reference

These mix ratios align with BS 8500 (Concrete: Complementary British Standard to BS EN 206) for prescribed mixes. For structural work subject to Building Regulations, always verify the required concrete specification with your structural engineer or Building Control.

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Last updated: February 2026

All calculations are estimates. Verify with your supplier.

Concrete Mix Calculator — Cement, Sand & Aggregate Quantities