Screed Volume Calculator
Screed volume is simply the floor area multiplied by the screed thickness, with the thickness converted from millimetres to metres.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the floor area in square metres and the finished screed thickness in millimetres.
- Optionally add a waste / over-order percentage (10% is common for hand-laid screed) and a coverage-per-bag figure if you are buying bagged screed.
- Read the total volume in m³ and litres; use the bag count to order material.
How it works
Screed volume is simply the floor area multiplied by the screed thickness, with the thickness converted from millimetres to metres. The tool then inflates that net figure by your waste allowance to cover spillage, uneven substrates and setting-out losses: volume = area × (thickness ÷ 1000) × (1 + waste% ÷ 100).
The result is reported in cubic metres and litres (1 m³ = 1,000 L). If you supply a coverage-per-bag figure the tool divides the total volume by the bag yield and rounds up, since you cannot buy a part-bag. All figures are estimates — actual usage depends on how level the substrate is and whether the screed follows a fall or ramps up to thresholds.
Worked example
25 m² floor at 50 mm with 10% waste. A living-room floor is 25 m² and gets a 50 mm sand-cement screed. Enter area 25, thickness 50 and waste 10%. Net volume = 25 × 0.050 = 1.250 m³; with 10% waste = 1.250 × 1.10 = 1.375 m³ (1,375 litres). If a bag covers 0.01 m³, that is ceil(1.375 ÷ 0.01) = 138 bags.
Common mistakes
- Entering the thickness in centimetres or metres instead of millimetres — a 50 mm screed is 0.05 m, not 50 m.
- Ordering the exact net volume with no waste allowance; hand-laid screed almost always over-runs on uneven floors, so add 5–15%.
- Mixing up floor screed with structural concrete — screed is a thin topping/levelling layer, not a load-bearing slab, so do not use this for slab or footing pours.
Frequently asked questions
How thick should floor screed be?
A bonded sand-cement screed is typically 25–40 mm, an unbonded screed 50 mm or more, and a floating screed over insulation 65–75 mm. Always follow the manufacturer's and your engineer's specification for your build-up; this tool only computes volume from the thickness you enter.
How many bags of screed do I need?
Enter a coverage-per-bag figure (m³ per bag) and the tool divides your total volume by it and rounds up. Bag yields vary by product and thickness, so take the figure from your bag's datasheet rather than assuming a value.
Does the calculator include an over-order allowance?
Only if you enter one. Leave the waste field blank for the exact net volume, or add a percentage (10% is a common default) to cover spillage and uneven substrates.
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