Screed calculator
Calculate the volume of sand-cement screed needed for a floor, plus an approximate bag count if you're using bagged screed mix.
Result
Screed volume
25kg bags (approx.)
How to use this tool
- Measure the floor area.
- Set your screed depth — 50mm is a common bonded-screed thickness; unbonded/floating screeds are often thicker.
- Read the volume and approximate bag count.
Assumptions
- Constant depth across the whole floor area.
- Bag yield is an approximation — check your specific screed product's stated yield.
Technical details: what the fields mean
- Floor area
areaM2 - Floor area to be screeded, in square metres.
- Screed depth
depthMm - Screed thickness, in millimetres. Check your floor build-up (bonded, unbonded or floating screed have different minimum depths).
Methodology
Geometric screed volume = floor area × depth. The separate approximate bag count divides that volume by an assumed 0.0125m³ yield per 25kg bag and rounds up; actual yield depends on the selected screed product, so check its stated yield.
Worked example
20m² room, 50mm bonded screed
Inputs: Floor area: 20 m², Screed depth: 50 mm
Result: 1.0 m³ (approx. 80 x 25kg bags)
Practical guidance
- For areas above roughly 1m³, ready-mixed flow screed delivered by pump is usually far more practical than bagged mix.
- Confirm minimum screed depth with your specific screed type — floating screeds over insulation typically need to be thicker than bonded screeds.
Common mistakes
- Using a bonded-screed depth (thinner) when the floor build-up actually requires an unbonded or floating screed (thicker).
- Entering depth in centimetres instead of millimetres.
FAQs
What depth of screed do I need?
It depends on the screed type: bonded screeds are often around 25–40mm, floating/unbonded screeds are typically 50mm or more. Confirm with your screed manufacturer's guidance for your specific build-up.
How much screed volume is in a 20m² room at 50mm?
1.0 cubic metre.
Last reviewed: 2026-10-11
Assumes constant depth; does not account for falls, screws or underfloor heating pipe encapsulation depth.
This tool provides an indicative estimate, based on the assumptions stated above.
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