Sand And Cement Mix Calculator

It works out how much cement and sand you need for a general sand-and-cement job - patio or paving slab bedding mortar, a floor or wall screed, or any other sand-and-cement bed - from the area, depth and mix ratio you enter, rather than assuming one fixed job type.

5:1 (sand:cement) is the most common UK trade default for bedding mortar under paving slabs, matching pavingdirect.com's published "Bedding Mortar (5:1) Calculator" (checked 2026-08-08). This calculator uses 5:1 as its default and Patio Or Slab Bedding Mortar preset.

UK screed guidance summarising BS 8204-1 (checked 2026-08-08) puts the cement:sharp-sand ratio at roughly 1:3 to 1:5 for a traditional sand and cement screed. This calculator's Floor Or Wall Screed preset defaults to a 4:1 (sand:cement) mix, a reasonable general-purpose choice within that range - check your specific screed spec if you have one.

Around 50mm is a common trade default for a sand-and-cement bedding layer under paving slabs, which is why this calculator's Patio preset defaults to 50mm. Thicker beds are sometimes used to make up levels, but a pure sand-and-cement bed over about 100mm is unusual.

Pure sand-and-cement mixes are a bedding or screed material, not a structural fill. UK trade practice generally moves to a concrete (cement plus aggregate) base once you need more than about 100mm of material, since concrete is more economical and structurally appropriate at that thickness. This calculator's Assessment module flags deeper "beds" so you can double-check you're using the right material.

Wet volume is the volume the finished, mixed mortar will occupy once placed (area x depth). Dry volume is how much loose sand and cement you actually need to buy and mix, which is larger - about 33% more, per the standard construction "1.33 bulking factor" (checked 2026-08-08) - because dry sand contains a lot of air voids that collapse once water is added and the mix compacts.

It depends on your depth and mix ratio, which is exactly why this calculator asks for both rather than giving a single fixed "per m²" figure - a 25mm skim needs a fraction of the materials of a 75mm screed at the same area. Enter your own area and depth above for an exact figure.

This calculator is built around a rectangular area and depth, which suits beds, screeds and slabs well but is an awkward fit for pointing (a linear joint, not an area). For a small pointing or patch-repair job, you can still use the calculator with a small notional area and shallow depth to get a rough materials estimate, but a dedicated per-metre pointing calculation will be more accurate for that specific job.

No. Concrete includes a coarse aggregate (gravel or ballast) alongside sand and cement and uses a different bulking factor (1.54, versus 1.33 for plain mortar) because of that aggregate. This calculator is for plain sand-and-cement mixes only - see CoryVu's ballast-and-cement-calculator-for-shed-base for an aggregate-based concrete mix.

3:1 (sand:cement) is a much richer, stronger mix normally reserved for repairs, heavy-duty use, or where extra strength is specifically needed. For a standard patio bedding mortar or general screed, 4:1-6:1 is the usual UK trade range and is considerably more economical on cement - this calculator's Assessment module flags 3:1 selected over a large area as worth double-checking.

10% is a commonly used default safety margin covering typical spillage and minor over-mixing on a straightforward job. Use 15-20% if your area is irregular, sloped, or you want a comfortable buffer rather than an emergency extra trip to the merchant.

Sharp sand is the standard choice for screeds and concrete, giving a stronger, less workable mix; building (soft) sand is more commonly used for bedding mortar and general pointing work, where a smoother, more workable mix matters more. Check which your specific job calls for - this calculator estimates quantities either way, since the volume/weight maths is the same regardless of sand type.

As a rough rule of thumb used in UK screed guidance, allow about 1mm of depth per day of drying for the first 50mm, then progressively longer per additional millimetre beyond that - so a 50mm bed might need roughly 6-8 weeks before it's considered fully dry, though it will be firm enough to work on much sooner. Always check the specific guidance for your product and the weather conditions at the time.

No. It estimates cement and sand quantities from your area, depth and mix ratio using standard UK trade and construction-industry reference figures. It does not check structural adequacy, screed build-up against BS 8204-1, curing conditions, or substrate preparation.