Floor Screed Calculator UK
Calculate how much floor screed you need by weight and bags. Works for sand:cement, anhydrite and rapid-set screed. Enter floor area and depth to get your estimate.
Enter your floor details
Total area to be screeded
Typical: 40mm (bonded), 65mm (unbonded), 50-75mm (over UFH)
Covers cuts, breakages and uneven ground. 10% is a typical starting point.
Floor screed estimate
Enter floor area and screed depth to see your estimate
How to calculate floor screed quantities
Floor screed volume is straightforward: volume (m3) = area (m2) x depth (m). Weight depends on the screed type - sand:cement screed is denser than anhydrite, so you need more kg for the same volume.
For pre-mixed bagged screed, divide the total weight by the bag size to get bag count. Most pre-mixed screed bags are 25kg with a yield of approximately 0.012 m3 per bag.
For larger areas - typically over 50-100 m2 - ready-mixed or pumped screed is usually more cost-effective and practical than mixing bags. A screed pump can lay large areas quickly and to a consistent depth.
Screed depth by application type
| Application | Typical depth | Note |
|---|---|---|
| Bonded (to primed concrete) | 25-40mm | Substrate must be clean and primed |
| Unbonded (over polythene separator) | 50-75mm | Minimum 50mm, 65mm recommended |
| Floating (over insulation) | 65-75mm | Reinforcement mesh often recommended |
| Over underfloor heating | 65-75mm | Min 25mm cover over pipes |
Screed type comparison
Sand:cement screed is the traditional choice. It is mixed on site (or ordered ready-mixed), robust and widely understood. The main drawback is labour intensity and drying time.
Anhydrite (liquid) screed is pumped and self-levels to some extent. It is excellent over underfloor heating because it flows around pipes. However it must be sealed before tiling (anhydrite reacts with tile adhesive) and requires ventilation to accelerate drying.
Rapid-set screed uses a modified binder that allows early foot traffic - typically 4-8 hours - and faster drying than traditional sand:cement. More expensive per bag but reduces programme time on time-critical projects.
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Frequently asked questions
Planning estimates only
These results are estimates for planning purposes only. Actual material quantities can vary based on site conditions, compaction, wastage, product size, installation method and supplier guidance. For structural, safety-critical or regulated work, always consult a qualified professional.