What you need to know
- Area × thickness × product consumption gives the base quantity.
- Add waste and round up to full bags.
- Different mortars have different yields and working limits.
Use your own measurements
Use the linked BricoDato resource to check these inputs in your own situation. Mortar and tile adhesives vary greatly in use and working properties.
Use the technical data sheet
Tile adhesive, repair mortar and screed products can have very different kg/m² consumption. Enter the value for the product you intend to use.
Thickness changes the quantity quickly
If the application thickness doubles, material use is close to doubling. On uneven substrates, measure several points before choosing an average.
Round up to complete bags
Buying the exact mathematical quantity is rarely possible. Use full bag sizes and leave a small reserve rather than running short mid-job.
Respect mixing instructions
Water ratio, mixing time, pot life, open time and application temperature can all affect performance.
A mortar estimate that uses product consumption
Mortar and tile adhesives vary greatly in use and working properties. For a quantity estimate, use the product's consumption in kg per square metre per millimetre of layer thickness where the manufacturer supplies it.
Example to adapt
For 12 m² at a nominal 5 mm layer with illustrative consumption of 1.6 kg/m²/mm, the base need is 12 × 5 × 1.6 = 96 kg. An 8% allowance gives 103.68 kg. At 25 kg per bag, round 103.68 ÷ 25 upward to 5 complete bags. At a hypothetical €9 per bag, that is €45 in material.
| Average layer | Mass before allowance | 25 kg bags after 8% |
|---|---|---|
| 3 mm | 57.6 kg | 3 |
| 5 mm | 96.0 kg | 5 |
| 8 mm | 153.6 kg | 7 |
Checks before acting
- Confirm whether the product specifies consumption per millimetre or a different measurement basis.
- Check permitted minimum and maximum layer thickness; a levelling product is not interchangeable with tile adhesive.
- Follow water ratio, pot life and application-temperature limits.
- Check substrate condition and cure times before proceeding with finishes.
Final check
The product datasheet, required thickness and job type should determine dry-mortar quantity. As an illustrative calculation, if a particular approved product states 18 kg/m² at 10 mm, a 12 m² area needs 216 kg; with 25 kg bags, round 216 ÷ 25 up to nine bags before any realistic handling allowance. Do not reuse that yield for a different mortar or thickness.
- Use product-specific consumption.
- Measure realistic average thickness.
- Round up to full bags.
- Respect water ratio and working time.
Keep a small job sheet
Write down product reference, kg/m²/mm, area, thickness, allowance, bag weight and mixing time.
Turn the guide into a decision
Write down the chosen manufacturer's kg/m² figure, water dosage, pot life and required substrate preparation. Fixed ratios from an unrelated product can produce a weak or incompatible mix; use qualified design where structural strength, waterproofing or exposure class matters.