Practical guide
Self-Levelling Screed Bags and Consumption
Use the exact levelling product consumption, bag size and permitted thickness before rounding a purchase to whole bags or packs.
Updated 16 October 2026
Reviewed by the 99Tools team. Editorial and corrections policy.
Choose the actual levelling product
Complete bagged screeds and self-levelling compounds have their own binder system, substrate requirements, thickness range and intended finish. Some products form an underlayment for another floor covering rather than a final wearing surface. A name containing screed does not establish that it is interchangeable with a site-mixed sand-and-cement layer or another manufacturer’s product. Use the exact locally supplied specification.
Understand kg per square metre per millimetre
When a manufacturer supplies kg/m²/mm, multiply net floor area by average thickness in millimetres and that rate. Apply one additional allowance if it is not already in the agreed consumption. Then divide dry mass by the complete bag mass and round up. The rate is for the selected product and stated conditions; it is not a universal density or a guarantee of site consumption.
A complete-product arithmetic example
For a hypothetical 20 m² floor at 5 mm, a chosen consumption of 1.7 kg/m²/mm gives 170 kg before allowance. A selected 10% extra makes 187 kg. In hypothetical 20 kg bags, ten whole bags cover that calculated mass. If sold only in packs of four, purchase twelve bags. These figures illustrate purchasing arithmetic and do not name a product, permitted application or standard bag size.
Finished-yield method
Some complete products give usable finished litres per bag. Use that declared yield with installed volume including one allowance, rather than trying to derive litres from dry bag mass or added water. For a hypothetical 0.11 m³ material target and 12 L yield, divide 110 by 12 and round up to ten bags before any pack increase. The 12 L value is an example, not a verified universal screed yield.
Confirm thickness and substrate limits
A consumption calculation does not prove that a product permits the selected depth. Check the actual minimum and maximum layer thickness, substrate condition, required primer and complete system. Do not add aggregate, cement, sand or extra water simply to stretch the calculated yield unless the product instructions require the specified procedure. Separate products or different layer constructions need their own take-off and quantities.
Drying, covering and quote comparisons
Read the selected product requirements for application, curing, drying and readiness for the intended tile, vinyl, timber or other finish. These depend on system and conditions, so there is no universal drying time inferred from the thickness input. 99Tools is independent of Cashbuild and manufacturers. Compare the same area, thickness, consumption, bag size, allowance, pack count and VAT basis. Delivery, preparation, labour and pump charges may be separate. UK product data should not automatically replace South African product specifications.
Use the related calculators
Apply the explanation above with your own figures. Open a calculator below, check every input and review the result assumptions before making a decision.
Frequently asked questions
Is kg/m²/mm the same as kg/m²?
No. A per-mm rate must also be multiplied by the selected thickness in millimetres.
Can I convert a bag’s dry kilograms directly to finished litres?
No. Use the declared finished yield when choosing that method.
Does the tool choose a primer or thickness limit?
No. Those requirements come from the complete product and floor system.
Are self-leveling and self-levelling different calculator methods?
They are spelling variants here. The exact product specification still determines the calculation inputs.