Tile Adhesive Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/8/2026
The amount of tile adhesive is calculated by multiplying the surface by the consumption per m² (which depends on tile size), with a waste margin. For 20 m² of medium tiles (about 2.75 kg/m²) with a 10% margin, you need 3 bags of 25 kg.
Explanation
The amount of adhesive needed depends heavily on the size of the tiles being laid, since it determines the recommended trowel notch size (the toothed edge of the trowel): the larger the tiles, the more adhesive is needed to ensure sufficient grip over the whole contact surface, so the wider the trowel notches must be. Small tiles (15 × 15 cm or less) with a fine 4 mm notch generally consume 1.5 to 2 kg/m², while very large tiles (45 × 45 cm and up) with a wide 10 to 12 mm notch can consume 4 to 5 kg/m². This calculator applies an indicative average value for each size category; the adhesive manufacturer and tile supplier generally provide a more precise recommendation on the packaging. A waste and breakage margin (10% in common use) is added to compensate for mortar left in the bucket, on the trowel, or lost during installation adjustments.
Example: 20 m² of medium tiles (20×20 cm)
Inputs
Surface: 20 m². Size: medium. Margin: 10%.
Calculation
Adhesive needed = 20 × 2.75 × 1.10 = 60.5 kg. Bags of 25 kg = round up(60.5 ÷ 25) = 3.
Result
You need to plan for 3 bags of 25 kg adhesive for this surface.
Frequently asked questions
Should single or double buttering be used?
Single buttering (adhesive applied only to the substrate) is generally sufficient for standard-size tiles indoors. Double buttering (adhesive also applied to the back of the tile) is recommended for large formats, outdoor use, or high-traffic areas, and increases adhesive consumption by about 1.5 to 1.8 times compared with single buttering — this calculator assumes single buttering.
Is consumption the same on floors and walls?
Consumption mainly depends on the trowel notch size used, regardless of the surface being tiled (floor or wall). However, the adhesive itself sometimes differs: some adhesives are specifically formulated for better vertical hold (walls), which is worth checking on the chosen product's packaging.
How do you choose the right trowel notch size?
The general rule is to increase the notch size along with the tile size: a fine notch for small formats, a wide notch for large formats and thick tiles (porcelain stoneware in particular). The adhesive manufacturer generally indicates the recommended notch size for each tile format on the product packaging.