Concrete Mix Ratio Calculator
Calculate exact material quantities for mixing concrete from scratch. Enter your target volume and mix ratio to get cement, sharp sand, and aggregate quantities.
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Concrete Mix Guide
What should I know about Mix Ratios Explained?
A 1:2:4 mix means 1 part cement to 2 parts sand to 4 parts aggregate by volume. Higher cement content (1:1:2) gives stronger concrete but is more expensive and prone to shrinkage cracking. For most DIY domestic applications, C20 (1:2:4) is appropriate.
What's the key thing to understand about Water-Cement Ratio?
The w/c ratio is the weight of water divided by the weight of cement. Lower = stronger. C20: w/c = 0.55. C25: w/c = 0.50. C30: w/c = 0.45. Adding excess water is the most common mistake — it weakens concrete significantly. Add water slowly until workable.
What's the key thing to understand about Consistency Check?
Slump test: fill a cone mould, lift, measure slump. For domestic slabs, 75–100mm slump. For foundations, 50–75mm. For highly reinforced concrete, up to 125mm. Concrete that flows off the shovel is too wet.
What's the key thing to understand about Safety and Regulations?
Most structural and electrical DIY work in England and Wales must comply with Building Regulations and is notifiable to local Building Control. Work that is not notifiable (like-for-like replacements, cosmetic changes) can be done without notification. Notifiable work done without approval is technically illegal and can cause problems when selling the property. Electrical work in most rooms requires a Part P competent person or Building Control inspection. Gas work must always be performed by a Gas Safe registered engineer — it is illegal for anyone else to carry out gas work in the UK, and using an unregistered installer invalidates both your home insurance and any warranty on the work. For structural changes (removing load-bearing walls, altering the roof structure), always get a structural engineer's assessment before starting, even for jobs that look straightforward.