MixCalc is a free cement and ballast ratio calculator built for UK DIYers. It calculates exactly how much ballast, sand, cement, and gravel you need for concrete projects — whether you're laying a shed base, building a garden path, or pouring footings.
Figuring out concrete ratios shouldn't require a maths degree. Most builders' merchant websites either don't have a calculator at all, or bury it behind registration forms. We wanted a tool that gives you an instant answer: enter your dimensions, pick your mix ratio, and see exactly how many bags or tonnes to order.
The calculator supports both ballast (a pre-mixed aggregate of sand and gravel) and separate sand/gravel mixes. It uses standard mix ratios (1:3, 1:4, 1:5 by volume) and converts the result into bags, bulk bags, or tonnes — whichever your local merchant sells in. A 10% waste buffer is included automatically because in practice you always lose some to spillage and uneven ground.
A 1:4 mix means 1 part cement to 4 parts ballast by volume. This produces roughly C20 grade concrete — strong enough for shed bases, paths, and most domestic foundations. A stronger 1:3 mix is suitable for structural footings, while a weaker 1:5 mix works for non-structural fill. If you're unsure which ratio to use, 1:4 is the safe default for most garden projects.
All calculations are based on standard industry ratios and material densities. Cost estimates use average UK builders' merchant prices. Your actual costs may vary by region and supplier. For structural work, always consult a qualified builder.
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