Tile Adhesive Calculator
The spread rate is set by the trowel notch, not by the brand — roughly 3 kg/m² with a 6 mm notch, 4.5 kg/m² at 10 mm and 5.5 kg/m² at 12 mm, and double that if you back-butter large tiles or work over an uneven floor. That is why the rate is an input rather than a built-in product. Ten square metres at a 10 mm notch is 45 kg; add 10% waste for 49.5 kg, which is two 25 kg bags, since one bag covers 5.6 m².
Your numbers
Bags needed
2bags
Adhesive needed
49.5kg
Area one bag covers
5.56m²
Formula
Adhesive needed = Area × Adhesive per m² × (1 + Waste allowance ÷ 100), Bags needed = ⌈Adhesive needed ÷ Bag weight (kg)⌉
Spread it thin and the tile is only partly bedded — the cracks appear months later, so this is not the place to economise. Opened cement-based adhesive hardens with humidity, so a part bag rarely lasts until the next job.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Area (m²)The space a shape covers — length squared. | 10 | 0 and up |
| Adhesive per m² (kg)Adhesive spread on one square metre, set by the trowel notch — about 3 kg at 6 mm, 4.5 kg at 10 mm. | 4.5 | 0 and up |
| Bag weight (kg)The weight of one bag; 20, 25 and 40 kg are common and printed on the front. | 25 | 0 and up |
| Waste allowance (%)The extra bought to cover breakage and offcuts. | 10 | 0 ~ 50 |
Step by step
Quick reference table
Results when only Area (m²) changes and everything else stays put.
| Area (m²) | Bags needed (bags) | Adhesive needed (kg) | Area one bag covers (m²) |
|---|---|---|---|
| 5 | 1 | 24.8 | 5.56 |
| 7.5 | 2 | 37.1 | 5.56 |
| 10 | 2 | 49.5 | 5.56 |
| 15 | 3 | 74.3 | 5.56 |
| 20 | 4 | 99 | 5.56 |
What each result means
| Result | At default values |
|---|---|
| Bags needed (bags)How many bags to buy; they are not sold in fractions, so this rounds up. | 2 |
| Adhesive needed (kg)The weight of adhesive to buy, waste included. | 49.5 |
| Area one bag covers (m²)How much area one bag covers at that spread rate — a sanity check on the count. | 5.56 |
Common mistakes
Spread it thin and the tile is only partly bedded — the cracks appear months later, so this is not the place to economise. Opened cement-based adhesive hardens with humidity, so a part bag rarely lasts until the next job.
Glossary
- Area
- The space a shape covers — length squared.
- Adhesive per m²
- Adhesive spread on one square metre, set by the trowel notch — about 3 kg at 6 mm, 4.5 kg at 10 mm.
- Bag weight (kg)
- The weight of one bag; 20, 25 and 40 kg are common and printed on the front.
- Waste allowance
- The extra bought to cover breakage and offcuts.
- Bags needed
- How many bags to buy; they are not sold in fractions, so this rounds up.
- Adhesive needed
- The weight of adhesive to buy, waste included.
- Area one bag covers
- How much area one bag covers at that spread rate — a sanity check on the count.
Frequently asked questions
Q. How is Tile Adhesive Calculator calculated?
Adhesive needed = Area × Adhesive per m² × (1 + Waste allowance ÷ 100), Bags needed = ⌈Adhesive needed ÷ Bag weight (kg)⌉ — The spread rate is set by the trowel notch, not by the brand — roughly 3 kg/m² with a 6 mm notch, 4.5 kg/m² at 10 mm and 5.5 kg/m² at 12 mm, and double that if you back-butter large tiles or work over an uneven floor. That is why the rate is an input rather than a built-in product. Ten square metres at a 10 mm notch is 45 kg; add 10% waste for 49.5 kg, which is two 25 kg bags, since one bag covers 5.6 m².
Q. Can you walk through an example?
With Area 10m², Adhesive per m² 4.5kg, Bag weight (kg) 25, Waste allowance 10%, the answer is Bags needed 2bags.
Q. What do I need to enter?
Enter Area, Adhesive per m², Bag weight (kg), Waste allowance. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Area (m²) moves the answer to Area (m²) 5 → Bags needed (bags) 1 and Area (m²) 20 → Bags needed (bags) 4. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Spread it thin and the tile is only partly bedded — the cracks appear months later, so this is not the place to economise. Opened cement-based adhesive hardens with humidity, so a part bag rarely lasts until the next job.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.