Example 1
- Area: 18 m²
- Consumption: 3.5 kg/m²
- Waste: 10%
- Bag size: 25 kg
You need 69.30 kg of adhesive
That equals 3 full bags
How much thinset for 18 m²? 3.5 kg/m² × 10% → 69.30 kg (3 bags of 25 kg).
Thinset Calculator
Enter area in m² and coverage from the bag or the trowel notch. The calculator multiplies area by kg/m², adds waste, and rounds bags up. An 18 m² room at 3.5 kg/m² and 10% is 69.30 kg, three 25 kg bags. A 7.2 m² bath at 4.0 kg/m² and 8% is 31.10 kg, two 20 kg bags.
Results
Area (m²), Consumption (kg/m²), Waste / spare (%) and Bag size (kg). The result shows up here.
Shopping estimate: kg from area and coverage, plus waste, then full bags. Need area first? Try floor area or tile quantity.
How the results are calculated
m²18
kg/m²3.5
Waste10%
Adhesive69.30 kg
The tile adhesive calculator finds kilograms and bags. The formula is area × coverage × type × (1 + waste/100), and bag count is kilograms divided by bag size, rounded up. Thickness in mm converts to coverage at about 1.5 kg/m² per millimeter.
An 18 m² room at 3.5 kg/m² and 10% waste is 69.30 kg, or 3 bags of 25 kg. A 7.2 m² bath at 4.0 kg/m² and 8% is 31.10 kg, two 20 kg bags. A large format on 24 m² at 5.2 kg/m² and 12% is 139.78 kg, six 25 kg bags.
Enter area in m² and coverage in kg/m² from the label. Waste, bag size, thickness, trowel notch, type, and price are optional. A comma in 3.5 works the same as a period.
Tile count lives on the tile-quantity page. A raw 5×4 m floor is on floor area and gives 20 m² to paste here. Adhesive follows area, not piece count.
Bags round up. 77 kg in 25 kg bags is 4 bags. Flex lifts the result by 10%: at 18 m², 3.5 kg/m², and 10% that is 76.23 kg.
Enter 18 and 3.5, set 10% and a 25 kg bag: 69.30 kg and 3 bags. Then 7.2 and 4.0 at 8% and 20 kg: 31.10 kg and 2 bags.
How to use this calculator
- Enter area in m², for example 18 for a room or 7.2 for a bath.
- Enter coverage in kg/m² from the label or pick a trowel notch. Thickness in mm is an alternative, about 1.5 kg/m² per mm.
- Set waste, usually 8–12%, and bag weight, for example 25 kg.
- Click Calculate. 18 m², 3.5 kg/m², and 10% give 69.30 kg, or 3 bags of 25 kg.
- Tile piece counts are on the tile-quantity page. This calculator returns adhesive mass in kilograms.
Formula
kg = area × coverage × type × (1 + waste/100)
bags = ⌈ kg ÷ bag size ⌉
Coverage comes from the label, a trowel notch, or thickness (about 1.5 kg/m² per mm). An 18 m² room × 3.5 × 1.10 = 69.30 kg → 3 bags of 25 kg.
Adhesive and bags
Area × coverage × type × (1 + waste), bags rounded up. An 18 m² room at 3.5 kg/m² and 10% is 69.30 kg, three 25 kg bags.
- kg/m²
- Coverage from the bag or notch. 3.5 on 18 m² plus 10% is 69.30 kg.
- m²
- Area to bond. 18 m² at 3.5 kg/m² is 3 bags of 25 kg, not a tile count.
- type
- Standard 1.0, flex 1.10, large format 1.25. Flex on 18 m² at 3.5 and 10% is 76.23 kg.
- zaokr.
- Round bags up. 77 kg in 25 kg bags is 4 bags.
Example scenarios
Example 2
- Area: 7.2 m²
- Consumption: 4.0 kg/m²
- Waste: 8%
- Bag size: 20 kg
You need 31.10 kg of adhesive
That equals 2 full bags
A 7.2 m² bath at 4.0 kg/m² and 8% → 31.10 kg (2 bags of 20 kg).
Example 3
- Area: 24 m²
- Consumption: 5.2 kg/m²
- Waste: 12%
- Bag size: 25 kg
You need 139.78 kg of adhesive
That equals 6 full bags
24 m² × 5.2 kg/m² × 12% → 139.78 kg (6 bags of 25 kg).
Example 4
- 20 m²
- 3.5 kg/m²
- 10% waste
- 25 kg bag
77.00 kg · 4 bags
20 × 3.5 × 1.10 = 77. 77 ÷ 25 = 3.08 → 4 bags.
Example 5
- 18 m²
- 4 mm bed
- 10% waste
- 25 kg bag
118.80 kg · 5 bags
4 mm × 1.5 = 6 kg/m². 18 × 6 × 1.10 = 118.80 → 5 bags of 25 kg.
Example 6
- 18 m²
- 3.5 kg/m²
- flex type (+10%)
- 10% and 25 kg bag
76.23 kg · 4 bags
18 × 3.5 × 1.10 × 1.10 = 76.23. Flex lifts the purchase by one bag versus standard.
Related calculators
Frequently asked questions
How do I calculate thinset from area and kg/m²?
Multiply area by kg/m², by the adhesive-type factor, and by (1 + waste/100). 18 m² × 3.5 × 1.10 → 69.30 kg, or 3 bags of 25 kg.
How many bags do I need for 18 m² at 3.5 kg/m², 10% waste, and a 25 kg bag?
3 bags. Mass 69.30 kg divided by 25 kg and rounded up. A 7.2 m² bath at 4 kg/m² and 8% needs 2 bags of 20 kg.
Is thinset the same as tile adhesive here?
Yes. This page uses the same kg formula for thinset / tile adhesive. It is not a tile-piece count and not a grout calculator.
How is adhesive amount calculated?
The calculator multiplies area by coverage (kg/m²), by the type factor, and by (1 + waste/100). Bag count is kilograms divided by bag size, rounded up. An 18 m² room at 3.5 kg/m² and 10% is 69.30 kg, or 3 bags of 25 kg.
Where does kg/m² come from?
From the bag label or a trowel-notch preset. Alternatively bed thickness in mm × about 1.5 kg/m² per millimeter. 4 mm is about 6 kg/m² before waste.
What waste should I add?
Usually 8–12%. An uneven floor and a large format tend toward the upper end. At 18 m², 3.5 kg/m², and 10% the result is 69.30 kg.
What does adhesive type do?
It multiplies the result. Standard = 1.0, flex = 1.10, large format = 1.25. At 18 m², 3.5 kg/m², and 10%, flex gives 76.23 kg instead of 69.30 kg.
How are bags counted?
Kilograms ÷ bag weight, rounded up. 69.30 kg in 25 kg bags is 3 bags. 77 kg in 25 kg bags is 4, because 77 ÷ 25 = 3.08.
Does tile count multiply adhesive?
No. The inputs are area and kg/m². 56 tiles from an 18 m² room do not change 69.30 kg while the area stays 18.
How is this different from tile quantity?
Here the result is kilograms and bags of adhesive. Tile quantity reports pieces. Take area from floor area or wall area.
Should I combine notch and bag coverage?
Pick one source. A notch preset fills kg/m². Two different entries break the scale. An 8 mm notch preset is 3.5 kg/m².
Does a comma in 3.5 work?
Yes. A comma and a period are the same coverage. At 18 m² and 10% the result stays 69.30 kg.
Does the result replace a product datasheet?
No. The calculator is a purchase estimate. The manufacturer and the substrate may need a different coverage per square meter.
Is this a free thinset calculator?
Yes. Enter area, kg/m², and waste and you see kilograms and bags at once. No account required.
Knowledge sources
Take coverage from the product datasheet. About 1.5 kg/m² per mm of bed is a practical rule when the label is missing. Mass units below from NIST.
Page updated October 12, 2026.