Floor Screed Calculator UK
Calculate the geometric volume of screed from a known floor area or room dimensions and the depth specified for your job. See cubic metres and litres first, then add only the allowance or product yield you actually intend to use.
Calculate your screed quantity
Use the depth from your project specification or chosen screed system. This calculator works out quantity only; it does not decide the correct screed type or thickness.
How the floor screed calculation works
Because 1 m² × 1 mm equals 1 litre. Divide litres by 1,000 for cubic metres.
Worked example
25 m² × 50 mm = 1,250 litres = 1.250 m³.
With the allowance left at 0%, the planning quantity remains 1.250 m³.
Area first, material choice second
The volume calculation is simple geometry. Current UK supplier calculators such as CEMEX and Holcim likewise ask for floor area/dimensions and screed depth to establish a volume. The calculator deliberately keeps that measured quantity separate from any ordering allowance or bag conversion.
Enter a known m² figure or calculate a simple rectangle from length × width. Split irregular floors into sensible sections rather than forcing one oversized rectangle.
Use the depth required by your actual screed system or project specification. This tool never chooses a “standard” thickness for you.
For delivered screed, work from m³. For bagged screed, optionally enter the manufacturer’s stated mixed yield in litres per bag.
Why there is no universal screed thickness here
Screed thickness depends on the system and product. Current ARDEX technical information, for example, publishes different minimum/application thicknesses for bonded, unbonded and floating screeds. Those are product/system specifications, not values a generic quantity calculator should silently impose.
If your drawings, installer or product datasheet states a depth, enter that number. If you do not yet know the required depth, resolve the specification before treating any material quantity as an order figure.
Bagged screed: enter finished yield, not just bag weight
A 20 kg or 25 kg bag does not tell you the exact volume of installed screed by itself. Pre-blended products publish their own coverage or mixed-yield information. ARDEX A 35 MIX, for example, publishes product-specific coverage for its 25 kg unit. That is why the optional bag field asks for litres of finished yield per bag from the exact product data rather than converting weight using a guessed universal density.
Buying traditional sand-and-cement screed?
Use this page to establish the finished screed volume first. If you then need to split a specified sand:cement mix, take that finished volume to the Sand & Cement Calculator, where ratio and conversion assumptions remain editable and visible.
What should I use for extra allowance?
There is no automatic 5% or 10% hidden in the answer. Level variation, measurement uncertainty, pump/handling loss and the way material is supplied can all affect an order, but one percentage is not correct for every job. The calculator therefore shows the base geometric volume first and starts the allowance at 0%.
Known area or length × width?
If you already have a reliable floor area from drawings or a measured take-off, use the known-area mode. For a simple rectangular room, length × width is enough. For L-shaped or multi-room work, calculate the sections separately with the Floor Area Calculator and enter the combined net area here.
Frequently asked questions
How do I calculate how much floor screed I need?
Multiply the net floor area in square metres by the specified screed depth in millimetres. That gives litres directly; divide by 1,000 for cubic metres.
Is 50 mm or 75 mm the standard screed thickness?
No single thickness is correct for every screed. Bonded, unbonded, floating, heated and proprietary systems can have different requirements. Use the depth specified for your actual system.
How many bags of screed do I need?
Enter the mixed/finished yield per bag stated by the manufacturer for the exact bagged product. The calculator then shows the theoretical count and rounds the purchase quantity up to whole bags.
Should I automatically add 10% waste?
No. The extra allowance starts at 0% so the measured volume stays visible. Add a percentage only when you have chosen one for the real job.
Can I use this for liquid or flowing screed?
The geometric m³ calculation works for any material laid over an area at a stated depth. Product suitability, minimum depth, pump requirements and ordering rules still come from the supplier/system specification.
Current UK sources checked for this page
- CEMEX UK — Screed Calculator: current supplier calculator using area and thickness to establish required screed volume.
- Holcim UK — Screed Calculator: current UK volume-calculation workflow using dimensions and depth.
- ARDEX UK — A 35 MIX: example of product-specific bag coverage.
- ARDEX UK — A 38: current technical information showing system-dependent screed thicknesses.
Quantity planning only. This calculator does not choose the screed system, mix ratio, structural build-up, minimum thickness, curing/drying regime or suitability for underfloor heating. Follow the project specification and current manufacturer/supplier information before ordering or installation.