Free Online Calculators
Calculate material & drying time
This screed calculator works out how much material you need and how long your screed will take to dry, based on the area, thickness, and screed type you enter. It uses standard construction benchmarks — for example, roughly 20 kg of cement screed per m² per cm of thickness. That way you can plan your purchase and schedule accurately before work begins.
Multiply the floor area by the finished screed thickness to get the volume, then convert that volume into cement and sand quantities using your mix ratio and the density of the mixed material. Add a small allowance for waste, uneven substrates and falls to drains.
Multiply the slab area by the slab thickness to get the volume of concrete — a twenty by twenty slab needs a different amount at every thickness, so the depth has to be fixed first. Order slightly more than the calculated volume to cover spillage and settlement into the sub-base.
A traditional sand and cement screed is mixed by volume with sharp sand making up the bulk and cement the smaller share, using only enough water for a damp, semi-dry consistency. Stronger ratios are used for heavy-duty floors, and additives or fibres can be added for thin or heated screeds.
The workable thickness depends on the type: bonded screeds are laid thinnest, unbonded screeds need more depth, and floating screeds over insulation or underfloor heating need the most. Going thinner than the manufacturer's minimum risks cracking, while excess depth slows drying and adds load to the structure.
The most common mistakes are adding too much water, poor substrate preparation, skipping the primer or damp-proof membrane, and failing to compact the screed properly. Rushing drying with heat or draughts, and omitting movement joints, also lead to curling and cracking.
Yes, provided the concrete is sound, clean, free of dust, laitance and contaminants, and prepared with a suitable bonding primer or slurry. If the concrete is weak, damp or unsuitable for bonding, lay the screed unbonded over a membrane instead.
Typical problems are cracking, curling at edges and joints, hollow or debonded areas, dusty or soft surfaces, and residual moisture that delays floor coverings. Most trace back to a poor mix, inadequate compaction, weak bonding or drying that was too fast or too slow.
Alternatives include self-levelling compounds for thin corrections, flowing anhydrite or calcium sulfate screeds, dry screed boards from gypsum fibre or chipboard, and a power-floated concrete slab finished as the wearing surface. The choice depends on depth available, drying time and the floor covering you plan to lay.
Poor man's concrete usually refers to a dry mix of cement and sand or gravel that is spread in place and left to harden with ground and rain moisture, without proper mixing, compaction or curing. It is far weaker and less durable than properly batched concrete and is only suitable for informal, non-structural uses.
Planning a flooring project? Whether you're working on a new build, renovation, or commercial construction, calculating the right amount of screed material is essential for a successful result. Our free screed calculator helps you determine exactly how much material you need and how long the drying process will take, saving you time, money, and unnecessary stress on site.
Screed is a thin layer of cementitious or anhydrite material applied to a subfloor to create a smooth, level surface ready for the final floor covering. It is used in homes, offices, warehouses, schools, and virtually every type of building. Getting the quantities right matters for several reasons:
Our calculator removes the guesswork and delivers accurate results in seconds.
The tool is designed to be intuitive and accessible for both professionals and DIY enthusiasts. Simply enter the following values:
The calculator instantly provides the material volume in cubic metres, weight in kilograms or tonnes, and an estimated drying time based on your inputs.
Cement screed is the most widely used type, valued for its strength, durability, and versatility. It works indoors and outdoors, and is compatible with underfloor heating systems. A general rule of thumb is that cement screed dries at a rate of approximately 1 day per millimetre of thickness, meaning a 50 mm layer takes around 50 days to fully cure under standard conditions.
Also known as calcium sulphate or flow screed, anhydrite screed is pumped onto the floor and self-levels, making it ideal for large areas and underfloor heating installations. It dries faster than cement screed – roughly 1 day per 1.5–2 mm – but must not be used in wet areas such as bathrooms or shower rooms.
Dry screed panels, typically made from gypsum fibreboard or chipboard, are laid without any wet process. They are immediately walkable and ideal for rapid refurbishments or where structural loading is a concern. No drying time is required, but careful subfloor preparation is essential.
One of the most critical aspects of any screed project is allowing sufficient drying time before laying the final floor covering. Installing tiles, carpet, hardwood, or vinyl too soon can trap moisture, leading to bubbling, warping, mould growth, and adhesive failure.
Key factors influencing drying time include:
Our screed calculator incorporates these variables to provide a realistic drying time estimate tailored to your specific conditions.
Imagine you're screeding a living room of 25 m² with cement screed at a thickness of 60 mm. Here's what the calculator would show:
These figures give you a solid basis for ordering materials, scheduling trades, and planning the overall project timeline.
It depends on the thickness. At 50 mm depth and a density of approximately 2,000 kg/m³, you'll need around 100 kg per square metre. Our calculator gives you a precise figure based on your actual inputs.
Cement screed typically needs around 1 day per millimetre of thickness. A 50 mm layer would therefore take approximately 50 days. Always conduct a moisture test before tiling to confirm readiness.
Light foot traffic is usually possible after 24–48 hours, but the screed will not be fully cured or ready for floor coverings for several weeks. Avoid heavy loads during this period.
Yes. The calculator accounts for the additional thickness required over heating pipes and cables, and adjusts drying time estimates accordingly for heated screed systems.
The minimum recommended thickness for a bonded screed is around 25 mm, while unbonded screeds should be at least 50 mm thick. Over underfloor heating, a minimum cover of 45 mm above the pipes is generally recommended.