Concrete Mix Calculator UK
Accurate material estimates for UK standard 25kg bags and tonnes.
Recommended: 10% for spillage and uneven ground.
Calculation Results
Ordering Ready-Mix? If you are ordering concrete for a large slab, mention you need m³. Most UK suppliers have a minimum order of 1m³.
Concrete Mixing Guide: Ratios, Bags & Best Practices in the UK
Understanding Concrete Mixes
Mixing concrete correctly is critical for the structural integrity of your project. In the UK, we use volume-based ratios (Cement:Sand:Aggregate) to determine the strength and durability of the final pour.
Whether you are pouring a small shed base, a garden path, or a structural foundation, using the correct concrete mix ratio ensures your work lasts for decades without cracking or degrading.
Quick UK Reference
- Standard Cement Bag:25kg (Standard UK DIY size)
- Bulk Bag Weight:Approx. 850kg - 1000kg (1 Tonne)
Common UK Concrete Mix Ratios
1:2:4 Ratio (Strong)
Used for structural foundations, garden paths, and heavy-duty shed bases. This is the most common DIY mix.
1:3:6 Ratio (Standard)
Ideal for general-purpose garden work, infilling, and non-structural bases where high strength isn't required.
1:1.5:3 Ratio (Very Strong)
High-strength mix for pre-cast items, reinforced concrete, or areas with high water exposure.
How to Calculate Manually
To calculate the volume manually, multiply the length, width, and depth (in metres).Volume (m³) = L × W × D
Always add 10% to your final number to avoid running short. Concrete is very difficult to "patch up" if you run out midway through a pour!
Ready-Mix vs Site-Mix
If your project requires more than 1 cubic metre, consider ordering Ready-Mixed Concrete.
- Site-Mix: More control, cheaper for small jobs, physically demanding.
- Ready-Mix: Guaranteed strength, very fast, requires clear access for a 10-tonne truck.
Expert Tips for a Perfect Pour
The Slump Test
Avoid adding too much water. Concrete should be the consistency of thick porridge. If it flows like water, it will be weak when dry.
Curing Time
Concrete takes 28 days to reach full strength, but you can usually walk on it after 24-48 hours. Keep it damp in hot weather to prevent cracking.
Concrete Mixing & Calculation FAQ
Structural Safety Disclaimer
This calculator provides estimates for general DIY purposes. For structural foundations, load-bearing walls, or safety-critical engineering, always consult a qualified structural engineer or local UK building control. Incorrect concrete strength can lead to structural failure.