Sand and Cement Mix Ratios: A Practical Guide to Mortar, Screed, Render and Concrete

"What is the mix for that?" is probably the most common question on any building site. The honest answer is that it depends on the job, the sand and the cement, so there is more than one right answer. This guide gives the commonly used ratios, hedged where they vary, and explains how to measure a mix properly. Always check the instructions on your cement bag and the specification for your project first, since they take priority over any general guide.

How mix ratios work

A mix ratio such as 1:4 means one part cement to four parts sand, measured by volume, not weight. Use the same container for each part, such as a bucket or gauging box, and keep the parts level. Parts are dry materials: the water goes in afterwards.

Less cement relative to sand gives a weaker, more workable mix. More cement gives a stronger, harder mix that can be more brittle and can shrink more. Consistency matters as much as the ratio, so measure every batch the same way.

Common ratios by job

Job	Typical mix (by volume)	Sand
Bricklaying and blockwork mortar	Roughly 1 cement to 4 to 6 sand, with plasticiser or lime	Building sand
Pointing	Similar to bricklaying mortar, matched to the existing wall	Building sand
Bedding paving slabs (mortar bed)	Commonly quoted at roughly 1 cement to 4 to 6 sand	Sharp sand
Screed	Often around 1 cement to 4 or 5 sand	Sharp sand
External render	Varies. One common approach is 1 : 1 : 6 cement, lime and sand	Plastering sand
General concrete	Around 1 cement to 5 or 6 all-in ballast	All-in ballast

These are typical figures rather than rules. Exposed walls, soft bricks, load-bearing work and frost-prone sites each call for a different approach, so use the specification for your job and ask a bricklayer or building professional if you are unsure.

Choosing the right materials

Sand

Match the sand to the job: building sand bulk bag for bricklaying and pointing, sharp / grit sand bulk bag for paving beds and screeds, and plastering sand bulk bag for render and base coats. Our guide to sharp sand vs building sand explains why.

Cement

We stock Blue Circle General Purpose cement in a 25kg paper bag, a 25kg Portland cement 42.5N, and Blue Circle Mastercrete, which contains an air entrainer for easier workability and improved frost resistance. If your cement already has an air entrainer, check the bag before adding a separate plasticiser.

Lime

Blue Circle Hydralime is a hydrated lime that can be added to cement, sand and lime mortars and renders. It improves workability, lightens the colour and makes floating renders and pointing easier.

Ballast

For concrete, all-in ballast bulk bag is a ready mix of sand and stone, which means you only need to add cement and water.

Mixing it properly

1. Measure the dry parts into a clean mixer or onto a clean board.
2. Mix the dry materials until the colour is even.
3. Add water gradually. Aim for a mix that holds its shape but is still workable. Too much water weakens the result.
4. Use it promptly. Mixed mortar and concrete start to set, and you should not "knock up" a stiffening batch with more water.
5. Protect it. Avoid pouring in frost or strong sun, and keep fresh work covered.

How much will I need?

The materials you buy are bulkier than the wet mix you make. A common rule of thumb is to allow roughly half as much again for concrete, and mortar behaves in a similar way. For a rule of thumb on bedding quantities per square metre, see our guide to sand and cement for paving bedding.

Safety

Cement is alkaline and can burn skin and eyes. Wear gloves, eye protection and a dust mask when mixing, and wash off splashes straight away. Hydrated lime is also caustic. Always follow the safety information on the packaging.

Frequently asked questions

What is the best ratio for bricklaying mortar?

There is no single answer. A common range is about 1 cement to 4 to 6 building sand, with plasticiser or lime, chosen to suit the bricks and the exposure. Ask your bricklayer or check the specification.

Can I mix sand and cement by weight?

You can, but volume is the usual method on site. If you measure by weight, remember that damp sand weighs differently to dry sand.

Does the type of cement matter?

Yes. General purpose cement suits most jobs. Check the bag for what it is intended for and follow its guidance.

How much water should I add?

Only enough to make the mix workable. Wetter mixes are weaker. Add water gradually and stop when it holds its shape.

Do I need ballast or sharp sand for concrete?

All-in ballast already contains sand and stone, so you only add cement. Sharp sand and gravel can be mixed separately if you prefer to control the proportions.

Ordering and delivery

You can browse the full range in our cement and aggregates collection. Bulk bags are sold at approximately 800kg each (the packed weight can be up to 850kg depending on moisture), and most sands and gravels are also available in 20 to 25kg trade packs for small jobs. Prices on our website are shown excluding VAT, and VAT is added at checkout.

We deliver to addresses in mainland England only; we do not currently deliver to Wales, Scotland, Northern Ireland or the islands. Timber, aggregates and cement have a minimum order of £250 ex VAT, and delivery is £25 ex VAT on orders under £500 ex VAT and free over £500 ex VAT. Bulk bags are delivered by Moffett lorry (truck-mounted forklift) and offloaded at your site, so someone must be there to receive them and you will need a firm, level area with suitable access. We do not offer next-day delivery. Our shipping policy has the full details, or call us on 03330 908479 or email sales@insulationwarehousedirect.co.uk if you would like a hand working out your order.

The quantities in this guide are estimates. Ground levels, how well the material is compacted and how wet it is all change what you need, and densities vary between quarries, so check the amount with your installer or the manufacturer's guidance before you order. Prices and pack sizes are correct at the time of writing.

Working out quantities? See our MOT Type 1 sub-base guide: how much do I need? or go straight to our aggregates calculator.