Free Concrete Mix
Calculator UK 2026
The most accurate concrete calculator UK for C10, C20, C25 and C30 grades. Use the sliders to set your dimensions and you will instantly get exact cement, sharp sand and aggregate quantities — in 25kg bags or bulk tonnes. Furthermore, all results use BS EN 206 mix design ratios, so the quantities reflect real UK construction standards. No sign-up required.
Concrete Grades Explained — C10 to C30
Choosing the right concrete grade is critical for any project. Using too weak a mix risks structural failure — however, using too strong a mix wastes money unnecessarily. Consequently, understanding what each grade does before you start is essential. Here is what each grade is designed for in UK residential construction.
Low-strength, non-structural applications only.
- Blinding under slabs
- Non-structural fill
- Bedding for kerbs
- Mass fill in trenches
Cement: ~190 kg/m³
Standard domestic grade for external flatwork. Not for structural elements.
- Garden paths & patios
- Driveways (light traffic)
- Garden steps
- Concrete posts
Cement: ~265 kg/m³
Most commonly specified grade for residential construction. Required by most structural engineers for house foundations.
- Strip foundations
- Trench fill foundations
- Ground floor slabs
- Reinforced beams
Cement: ~320 kg/m³
High-performance mix for demanding structural applications. Typically engineer-specified.
- Heavy vehicle loading
- Retaining walls
- Basement slabs
- Deep foundations
Cement: ~420 kg/m³
When to Site Mix and When to Order Ready-Mixed Concrete
The right choice depends on the volume of your pour, site access and timeline. Ready-mixed concrete is more consistent — however, for small jobs it is often not cost-effective. Therefore, the table below helps you decide which method suits your specific situation.
| Scenario | Recommended Method | Reason |
|---|---|---|
| Under 0.5m³ | Site mix — bagged materials | Cost-effective, no access issues, flexible timing |
| 0.5m³ to 1.5m³ | Site mix — bulk materials + mixer | Efficient with a hired mixer, better timing control |
| Over 1.5m³ | Ready-mixed concrete | Faster, more consistent, usually more economical |
| Structural foundations | Ready-mixed concrete | Guaranteed grade certification, less risk of weak spots |
| Hot weather pours | Ready-mixed concrete | Reduces workability issues, faster placement |
| Restricted site access | Site mix | Avoids large truck access issues on terraced sites |
In London, ready-mixed concrete costs approximately £120 to £195 per m³ depending on grade, supplier and access.
6 Rules for Mixing Concrete Correctly
A correctly mixed batch is as important as the correct grade. Furthermore, even the right grade will underperform if the mixing process is poor. These are the principles followed on every Signature Build project.
Water/Cement Ratio
Keep the water to cement ratio between 0.45 and 0.55. Never add extra water to make the mix more workable — it consequently weakens the finished concrete significantly and is the most common cause of premature failure.
Dry Mix First
Always mix cement, sand and aggregate together dry before adding water. This ensures even distribution throughout the batch and therefore prevents cement balling, which creates weak spots in the finished slab.
Small Batches
Mix in manageable batches that you can place and compact within 30 minutes. Furthermore, never mix fresh concrete into a partially set batch — this creates weak cold joints that can fail under load.
Order Extra
Our calculator includes a 10% overage. For foundations, do not reduce this — running short mid-pour consequently creates a cold joint, which is a serious structural defect that building control will flag.
Curing Time
Cover freshly poured concrete with polythene sheeting for at least 3–7 days. In addition, in hot or windy weather, dampen the surface regularly to prevent surface cracking and premature drying.
Same Batch
When ordering bagged materials, always buy from the same manufacturing batch. This ensures colour and aggregate consistency across the whole job — particularly important for exposed finishes such as driveways.
Concrete Calculator UK — FAQs
About This Concrete Mix Calculator — UK 2026
Signature Build Properties maintains this concrete calculator UK as a free tool for homeowners, contractors and self-builders planning groundworks, foundations and concrete flatwork across London and the South East. Our team has over 15 years of experience in structural concrete work. As a result, the mix ratios and overage allowances in this calculator reflect real site conditions rather than theoretical values.
How Mix Ratios Are Calculated
All mix ratios follow BS EN 206 concrete specification standards — the definitive UK reference for concrete mix design. Furthermore, material densities use standard UK values: cement at 1,440 kg/m³, sharp sand at 1,600 kg/m³ and 20mm aggregate at 1,680 kg/m³. Consequently, the quantities our calculator produces align with what suppliers will quote when you call to order.
Grades Covered
The calculator covers all four primary grades used in UK residential construction. C10 handles blinding and non-structural fill. C20 suits paths, driveways and garden slabs. C25 is the most widely specified grade for foundations and structural slabs. C30 covers heavily loaded elements such as retaining walls, basement slabs and reinforced beams. In addition, all results include a 10% overage allowance to prevent running short mid-pour.
When to Get a Written Quote
This calculator gives you an accurate material estimate for planning and budgeting. However, for projects requiring structural concrete — particularly foundations — always get a written specification from a structural engineer before ordering. Therefore, if your project involves foundations, basements or reinforced elements, call +44 7404 931629 to discuss requirements with our team before you start.
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Free Quote — West London
From groundworks and foundations through to full build completion. Furthermore, we handle all concrete specification in-house — no subcontracting. Based in Hayes and consequently covering all West London boroughs. Free site visit, no obligation.
