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Screed Calculator

Estimate floor screed volume, cement bags, sand quantity, dry materials, and project cost for sand-cement screeds. Supports Metric and Imperial units.

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Choose screed type, enter floor shape and dimensions, then calculate.

Dimensions

10%

Mix Ratio & Cement Bags

Material Cost Estimates (Optional)

Advanced Settings (Calculation Assumptions)

Calculation Results

Awaiting Calculations

Fill in the floor dimensions, screed depth, ratio parameters, and click Calculate to view estimates.

Formula Details

Floor Area Formula
Area = L × W (Rect) | S² (Square) | πD²/4 (Circle) | 0.5 × B × H (Triangle)

Computes physical surface area of the floor based on shape dimensions.

Variables Explained
  • L / W
    Length / Width:Horizontal dimensions of a rectangular floor.
  • S
    Side Length:Dimension of a square floor layout.
  • D
    Diameter:Straight-line span through center of a circular floor.
  • B / H
    Base / Height:Triangular floor layout bounds.
Screed Volume Formula (Wet)
Wet Volume = Area × Thickness

Estimates total wet space occupied by screed. Input dimensions are normalized to feet or meters.

Variables Explained
  • Area
    Floor Area:Calculated area of selected floor shape.
  • Thickness
    Screed Depth:Depth of the flooring layer (usually between 15 mm and 75 mm).
Dry Material Volume Formula
Dry Volume = (Wet Volume × (1 + Waste / 100)) × 1.33

Accounts for waste percentage and shrinkage. Unmixed dry ingredients shrink by ~33% when water is added because cement fills spaces between sand grains.

Variables Explained
  • Waste
    Waste Factor:User-specified waste allowance slider (defaults to 10%).
  • 1.33
    Dry Factor multiplier:Standard shrinkage engineering constant for dry sand-cement mixes.
Cement & Sand Quantities
Cement Vol = Dry Vol × (C / (C + S)) | Sand Vol = Dry Vol × (S / (C + S))

Calculates the volumetric proportions of dry ingredients from the mix parts (e.g., 1:4). Bulk densities are then applied to find total weights.

Variables Explained
  • C : S
    Mix Ratio Parts:Volumetric parts of cement to sand (e.g. 1 part cement to 4 parts sand).
  • Densities
    Bulk Densities:Bulk densities (Cement = 1440 kg/m³ or 90 lbs/ft³, Sand = 1600 kg/m³ or 100 lbs/ft³).

Calculation Example

Worked Example
Scenario

Calculate screed materials for a domestic living room measuring 5 meters by 4 meters with a 50 mm thick bonded sand-cement screed. The mix ratio is 1:4 (general domestic standard), waste allowance is 10%, and bag size is 25 kg.

Calculation Steps
  1. 1.Calculate floor area of the rectangular room.
    Area = 5 m × 4 m = 20 m²
  2. 2.Convert thickness to meters and calculate wet screed volume.
    Thickness = 50 mm = 0.05 m | Wet Volume = 20 m² × 0.05 m = 1.0 m³
  3. 3.Add 10% waste allowance.
    Wet Volume with Waste = 1.0 m³ × 1.10 = 1.10 m³
  4. 4.Convert to dry unmixed volume using the dry shrinkage factor (1.33).
    Dry Volume = 1.10 m³ × 1.33 = 1.463 m³
  5. 5.Estimate cement weight and bags (1:4 ratio).
    Cement Vol = 1.463 × (1 / 5) = 0.2926 m³ | Weight = 0.2926 m³ × 1440 kg/m³ = 421.3 kg | Bags (25 kg Bag) = ceil(421.3 / 25) = 17 Bags
  6. 6.Estimate sand volume and weight.
    Sand Vol = 1.463 × (4 / 5) = 1.1704 m³ | Weight = 1.1704 m³ × 1600 kg/m³ = 1872.6 kg
Final Quantity Needed17 Cement Bags (25 kg) & 1.17 m³ Sand
Worked Example
Scenario

Estimate screed requirements in Imperial for a commercial workspace floor measuring 40 feet by 30 feet. Screed thickness is 3 inches (heavy floating application), using a 1:3 mix ratio, 5% waste factor, and standard 94 lb bags.

Calculation Steps
  1. 1.Calculate floor surface area.
    Area = 40 ft × 30 ft = 1,200 sq ft
  2. 2.Convert thickness to feet and calculate wet volume.
    Thickness = 3 in = 0.25 ft | Wet Volume = 1,200 sq ft × 0.25 ft = 300 cu ft
  3. 3.Add 5% waste factor.
    Wet Vol with Waste = 300 cu ft × 1.05 = 315 cu ft
  4. 4.Convert to dry volume using dry shrinkage factor (1.33).
    Dry Volume = 315 cu ft × 1.33 = 418.95 cu ft
  5. 5.Calculate cement bags needed (1:3 ratio).
    Cement Vol = 418.95 × (1 / 4) = 104.74 cu ft | Weight = 104.74 cu ft × 90 lbs/cu ft = 9,426.6 lbs | Bags (94 lb bag) = ceil(9,426.6 / 94) = 101 Bags
  6. 6.Calculate sand volume and weight.
    Sand Vol = 418.95 × (3 / 4) = 314.21 cu ft (~11.64 yd³) | Weight = 314.21 cu ft × 100 lbs/cu ft = 31,421 lbs
Final Quantity Needed101 Cement Bags (94 lb) & 11.64 yd³ Sand

How to Use

Follow these simple steps to estimate the quantities of cement bags, sand, and cost requirements for your floor screed:

  1. Choose Screed Application: Select the application type (Traditional, Bonded, Unbonded, or Floating). Review the recommendations for thickness shown below the dropdown.
  2. Toggle Unit System: Choose Metric (m/cm/mm) or Imperial (ft/in/yd) at the top right of the calculator.
  3. Select Floor Shape & Dimensions: Choose your floor layout (Rectangle, Square, Circle, or Triangle) and fill in the required dimensions (length, width, or diameter) and target screed thickness.
  4. Specify Mix Ratio & Bag Weight: Choose a mix ratio (1:3 to 1:6, or enter custom cement:sand parts) and select your preferred cement bag size (20 kg, 25 kg, 40 kg, 50 kg).
  5. Optional Costs: Enter cement cost per bag and sand cost (per cubic unit or unit weight) in the cost section to estimate project material costs.
  6. Click Calculate: Review the detailed results containing area, wet screed volume, dry material volume, cement bag counts, sand volume/weight, and estimated cost.

Frequently Asked Questions

What is floor screed?
Floor screed is a thin layer of blended cement, sand, and water applied to a concrete subfloor to create a flat, level surface ready for the final flooring finish (such as tiles, carpet, timber, or vinyl). It is typically applied to level uneven substrates or to encase underfloor heating pipes.
What is the difference between screed and concrete?
Concrete is a structural material made of cement, sand, water, and large coarse gravel/aggregate that gives it extreme strength for structural elements like beams, columns, and slabs. Screed uses fine sand instead of coarse aggregates, creating a smoother, flatter finish specifically meant to provide a level floor surface.
Which mix ratio should I choose?
A 1:3 or 1:4 mix ratio (cement to sand by volume) is the industry standard. Use 1:3 for heavy traffic or commercial floors where higher durability and strength are needed. A 1:4 mix is standard and highly recommended for general domestic screed projects.
How much screed thickness do I need?
Screed thickness depends on the type. Bonded screed (adhered to concrete) can be thin, around 15 mm to 40 mm. Unbonded screed (separated by polythene) should be at least 50 mm thick to prevent curling. Floating screed (on top of insulation boards) must be 65 mm thick for domestic and 75 mm for commercial areas to resist weight loading without cracking.
How are cement bags calculated?
We determine the dry volume of cement required by dividing the total dry compacted volume by the mix ratio parts. Cement volume is multiplied by cement loose density (~1440 kg/m³ or 90 lbs/ft³) to get total weight. Finally, we divide total cement weight by your selected cement bag size (e.g., 25 kg) and round up to estimate whole bags.
Should I include a waste allowance?
Yes. Adding a 10% waste buffer is standard in flooring construction. This accounts for minor floor depressions, spillages, transport loss, and trimming on the job site, ensuring you don't run out of material before completion.

Need more material estimations?

Try our other masonry and construction calculators for concrete mix, plastering, cement blocks, brick layers, and ready-mix concrete to plan your project budget accurately.

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Disclaimer

Calculations are estimates based on the values you enter and standard engineering formulas. Results are intended for planning and estimation only. Always verify critical measurements, specifications, and local building requirements before purchasing materials or beginning construction.