Floor Screed Material Calculator
Volume to cement, sand and water by mix ratio.
With the default inputs: Area 100 m² · Thickness 30 · Mix ratio Cement mortar 1:3 etc.Mortar volume 3.15 m³
Edit the inputs below to recalculate.Inputs
Result
| Area × thickness | 3.00m³ |
| Volume incl. waste | 3.15m³ |
| Cement | 1.26t |
| Cement bags (50 kg) | 26bags |
| Sand | 1.42m³ |
| Sand weight | 2.13t |
| Mixing water (est.) | 0.76m³ |
Cement per cubic metre of mortar: about 400 kg for 1:3, 320 for 1:4, 270 for 1:5 and 230 for 1:6, with sand at 0.45-0.50 m³ per m³ and a bulk density of 1.5 t/m³. These are conversions of volumetric proportions; results shift with cement type, sand fineness and moisture. Below 20 mm use self levelling or a bonding agent, otherwise hollow spots and cracks appear; above 50 mm switch to a fine aggregate concrete bed.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Volume = area × thickness | divide mm by 1000 |
| Cement = per m³ (by mix) × volume | 400 / 320 / 270 / 230 kg |
| Sand = per m³ × volume | 0.45-0.50 m³/m³ |
| Water ≈ cement × 0.6 | w/c about 0.6 |
How to work it out
- Measure the area and fix the thickness. Use the average thickness: a floor that varies by 20 mm with a 20 mm minimum averages 30 mm, and costing at the minimum loses a third of the material.
- Volume = area × average thickness, plus 5-8% waste for handling, spillage and edges.
- Convert by mix ratio: 1:3 cement mortar is about 400 kg cement and 1.1 m³ sharp sand per m³; 1:4 about 320 kg and 1.2 m³.
- Round cement up to 50 kg bags; buy sand by m³ or tonne (sharp sand bulk density around 1.45 t/m³).
- Add bonding agent by area and curing water, and for large areas the saw cuts and filling of movement joints.
Where it goes wrong
- Costing at the minimum design thickness — a screed exists to level, so the average is always greater than the minimum and the minimum always runs short.
- Reading 1:3 as a weight ratio — mortar ratios are volumetric, one part cement to three parts sand by volume; mixing by weight adds cement, cuts sand and changes both strength and shrinkage.
- Walking on it the same day — pedestrian traffic within 24 hours dusts and debonds the surface; cure for 3-7 days and insulate in winter.
- No movement joints in large areas — over 36 m² or 6 m in one direction needs joints or shrinkage cracks are guaranteed.
Material and cost
Cement mortar screed at 30 mm costs 25-45 CNY/m² including labour; self-levelling 30-60 at 3-5 mm; reinforced fine concrete at 40 mm 45-70. Cement 400-500 CNY/t, sharp sand 100-180 CNY/m³.
On site
- Clean and dampen the substrate and prime it; a dry substrate draws the water out of the mortar and the screed shells off.
- Over underfloor heating use fine concrete with an accelerator, at least 40 mm thick, and only after the pipe pressure test passes.
- Accept at 4 mm under a 2 m straightedge; self-levelling needs 2 mm.
Basis
- GB 50209-2010 Code for acceptance of building floor construction, Chapter 4
- JGJ/T 175-2018 Technical standard for self-levelling floor compounds
- GB 50327-2001 Code for construction of residential decoration, Chapter 5
FAQ
Why does screed go hollow and crack?
Can self-levelling replace sand-cement screed?
1:3 or 1:4?
Cite this page
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Building Calculator. Floor Screed Material Calculator. 2026-10-25. https://jianzhujisuan.com/en/floor-screed