Floor Screed Calculator
Estimate the volume of floor screed for a room, then the materials for a traditional sand and cement mix, a pre-bagged screed, or a liquid screed ordered by volume.
Results
Enter your project measurements to see your results.
What the floor screed calculator does
Every screed estimate starts with the same figure: the volume of the finished layer. This page works that out from your floor area and average thickness, adds your waste allowance once, then turns the volume into whatever you are buying — cement and sand, bags of a proprietary product, or a delivered liquid screed.
Measuring the floor
- Measure the room length and width wall to wall at floor level.
- Split L-shaped or irregular rooms into rectangles and add the areas together.
- Exclude areas that will not be screeded, such as hearths or fixed plinths.
Estimating average thickness
Bases are rarely flat. Set a level line or laser at the finished floor height and measure down to the base at points across the room. Average the readings. Where insulation or underfloor heating pipes are involved, measure to the surface the screed will sit on.
Traditional, bagged and liquid screed
Traditional screed is mixed on site from sharp sand and cement and compacted by hand. Proprietary pre-bagged screeds are factory-blended and come with a stated yield. Liquid screeds are delivered ready-mixed and pumped into place. Each system has its own minimum and maximum thickness, curing and drying requirements, and conditions for bonded, unbonded or floating construction, so the right thickness depends on the product, not this page.
Worked metric example
A 5 m × 4 m room is 20 m². At an average 50 mm that is 1.0 m³, or 1.1 m³ with 10% waste. Using the editable starting assumptions (1:4 mix, 1.3 dry volume factor, 1,440 kg/m³ cement and 1,600 kg/m³ sand), that is roughly 412 kg of cement — 17 bags of 25 kg — and 1,830 kg of sand. With a pre-bagged product stating 12 litres per bag, the same volume needs 92 bags.
Worked imperial example
A 16 ft × 12 ft room at 2 in thick is 32 ft³, or about 1.19 yd³ before waste. Divide by the manufacturer-stated yield of your bagged screed, or give the volume to your liquid screed supplier.
Preparation, curing and suitability
Substrate preparation, priming, edge insulation, reinforcement, curing and drying times all depend on the screed system and its specification. This calculator estimates quantities; it does not confirm that a screed or thickness is suitable for your floor. For thin smoothing layers, see the self-levelling compound calculator, and for structural slabs the concrete slab calculator.
Frequently asked questions
- How do I calculate floor screed volume?
- Multiply the floor area by the average screed thickness. A 20 m² floor at 50 mm is 20 × 0.05 = 1 m³. Add your waste allowance once to get the quantity to plan for.
- Does a 1:4 mix mean I get exactly that much screed?
- No. A nominal ratio describes proportions by volume, not yield. Loose dry materials reduce in volume when mixed and compacted, so the calculator multiplies by an editable dry volume factor. Use figures from your supplier or specification where you have them.
- How many bags of pre-bagged screed do I need?
- Enter the yield per bag stated by the manufacturer of the product you are buying. The calculator divides the screed volume, including waste, by that yield and rounds up to whole bags.
- How is liquid screed ordered?
- Usually by volume from a supplier who delivers and pumps it. Suppliers set their own minimum orders, delivery charges and site requirements, so confirm them before booking. Enter a minimum order to see whether it applies.
- How thick should a floor screed be?
- That depends on the screed system, whether it is bonded, unbonded or floating, any underfloor heating and the manufacturer's or designer's specification. This calculator does not recommend a thickness.