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Concrete & screed · sand · cement
How much sand and cement for a floor screed?
Sand and cement screed to a finished depth, hand-mixed or bought in. 4:1 sharp sand to cement is the normal traditional screed; the old sheet ran 8:1 on ballast for a thicker oversite screed.
Measure it
Every box has its own unit next to it.
Change the unit beside any box and the number converts. The (i) beside each question says what the box wants and where the figure usually comes from. Anything marked per cent is a percentage of the quantity above it.
Check the rates
Rates and assumptions used
These are the figures the calculator works to. Change any of them and the order list updates — your merchant’s pack sizes and your own waste allowances beat the defaults every time.
Order list
The orange figure is the one you order to. Highlighted rows are the other numbers you order to. The small print under each row is the sum that produced it, so you can check it against your own take-off. Amber rows are warnings, not quantities.
How this one works
- Volume =
area × depth × (1 + waste %) - Dry volume = wet × 1.5, then split by the mix ratio and converted to weight
- Cement =
sand weight ÷ ratio
The figures the calculator works to. Every one can be changed in step 2, and your merchant’s pack sizes and your own waste allowances beat these defaults every time.
| Rate | Default | Why |
|---|---|---|
| Sand density | 1.6 t/m³ | Sharp sand, loose. |
| Dry-to-wet factor | 1.5 | |
| Cement bag | 25 kg | |
| Sand bulk bag | 0.85 t | |
| Fibres | 0.9 kg/m³ | Polypropylene fibres, optional but cheap insurance against cracking. |
A worked example
With the defaults the page opens on:
- How long is the room? 9 metres
- How wide is it? 7 metres
- How deep is the screed? 75 millimetres
- Which mix? 4:1 — traditional screed
- How much spare for waste? 5 per cent
Screed
- Area: 63 m²
- Depth: 75 mm
- Volume: 4.96 m³ — +5% waste
- Sharp sand: 9.53 t — mix 4:1
- Sand bulk bags: 12 bags — 9.5 / 0.85 tonnes a bag
- Cement: 96 bags — 2,381 kg
- Fibres: 4.5 kg — optional, at 0.9 kg/m³
- Or ready-mixed screed: 5 m³ — if you are buying it in
Change any figure above and every line recalculates; the small print under each row is the sum that produced it.
Questions people ask
How much sand and cement for a floor screed?
Volume × 1.5 for the dry materials, split by the mix ratio. A 9 m × 7 m room at 75 mm and 4:1 needs about 6 t of sharp sand and 60 bags of cement with 5% waste - the page shows the exact figures for your sizes.
What mix is a traditional screed?
4:1 sharp sand to cement by volume. 3:1 for a strong or thin bed, 5:1 for a floating screed over insulation.
How thick should a screed be?
75 mm unbonded, 65 mm floating over insulation, 40-50 mm bonded. Under 40 mm the calculator flags that a sand and cement mix is not the right material.
Should I add fibres?
Optional, cheap insurance against cracking: the calculator allows 0.9 kg of polypropylene fibres per cubic metre.
Calculators for the same job
Doing this for a whole job rather than one wall? SiteLedger keeps the valuations, supplier statements, invoices and variations against the project they belong to.
Read before you order. These work out quantities, not structural design — spans, lintels, rebar and foundation depths need an engineer and Building Control sign-off. Waste allowances are defaults, not promises: awkward cuts, long runs and bad weather all eat more than 5%. Where a merchant sells whole packs, the figure is rounded up to whole packs.