Example 1
- thickness 15 mm
- 1800 kg/m³, +5% waste
567 kg
This is a simple scenario that helps estimate the material scale for basic masonry or repair work.
Mortar requirement calculator
Type area, bed thickness, and density. The calculator turns net area into volume, then multiplies by density and waste. A 15 mm bed on 20 m² at 1800 kg/m³ and 5% is 567 kg. A 50 minus 5 m² wall at 10 mm, 1600 kg/m³, and 10% is 792 kg. A 15 m² floor 20 mm thick at 1500 kg/m³ is 472.5 kg.
Also useful: cement in mortar, mortar bags needed.
Results
Area, Layer thickness, Openings (area) and Mortar type. The result shows up here.
How the results are calculated
Mortar requirement counts kilograms from a bed. Net area is area minus openings. Volume in m³ is net times thickness. Mass is volume times density times (1 plus waste). A 15 mm bed is 0.015 m when the field wants meters, or 15 when the label is mm: read the unit on the field.
A 20 m² wall, 15 mm bed, 1800 kg/m³, and 5% waste is 567 kg. A larger 50 m² wall minus 5 m² openings at 10 mm, 1600 kg/m³, and 10% is 792 kg. A 15 m² floor 20 mm thick at 1500 kg/m³ and 5% is 472.5 kg. Bags from that mass live on mortar bags needed.
Type area and layer thickness. Openings, mortar type, custom density, and waste are optional. Type fills density; custom density overrides it. A comma in 15.0 works like 15.
Cement in that mass lives on cement in mortar: 1.00 m³ at 350 kg/m³ and 5% is 367.50 kg and 15 bags of 25 kg. Concrete 2.1 m³ from a 5×4×0.1 m slab is another calculator. Tile adhesive uses kg/m², not a masonry bed.
Bags round up on the next page. 567 kg at 25 kg is 23 bags, because 22.68 goes up. Empty openings deduct nothing. Typing 15 as 15 m of thickness instead of 15 mm overstates mass a thousand times.
Type 20, 15 mm, 1800, and 5%, click Calculate, and match 567 kg. Then 50 minus 5, 10 mm, 1600, and 10%: 792 kg.
How to use this calculator
- Type area in m², for example 20 or 50, and deduct openings when you have them.
- Enter layer thickness in the unit on the label. 15 mm on 20 m² at 1800 kg/m³ is the 567 kg base with 5%.
- Pick a mortar type or type a custom density in kg/m³ and waste, usually 5-10%.
- Click Calculate. 20 m², 15 mm, 1800, and 5% give 567 kg. 50 minus 5 at 10 mm is 792 kg.
- Bags and cement live on their pages. This calculator stays mortar mass.
Mortar 15 mm on 20 m²
Net area times thickness times density and waste. A 15 mm bed on 20 m² at 1800 kg/m³ and 5% is 567 kg.
- mm
- Bed thickness. 15 mm is 0.015 m. On 20 m² at 1800 kg/m³ and 5% that is 567 kg. 10 mm on 45 m² net is the other row.
- kg/m³
- Mortar density. 1800 on 0.015 × 20 × 1.05 is 567 kg. 1600 on 10 mm and 50−5 m² plus 10% is 792 kg.
- m²
- Area of the bed. 20 m² at 15 mm is that 567 kg. A 50 minus 5 m² wall at 10 mm is 792 kg.
Usage examples
Example 2
- 50 m² − 5 m² openings
- 10 mm, 1600 kg/m³, +10%
792 kg
With a larger amount of mortar, it is worth looking not only at volume but also at how the material will be mixed and supplied.
Example 3
- 15 m² × 20 mm
- 1500 kg/m³, +5%
472.5 kg
This example shows that even when the number seems small, mortar is still better calculated in advance than reordered later.
Related calculators
Frequently asked questions
How much mortar at 20 m², 15 mm, 1800 kg/m³, and 5%?
567 kg. Volume is 0.30 m³, then 0.30 × 1800 × 1.05. Bags still round up on the bags page.
How many kg at 50 m² minus 5 m², 10 mm, 1600 kg/m³, and 10%?
792 kg. Net 45 m², a 0.01 m bed, times 1600 times 1.10.
How many kg at 15 m², 20 mm, 1500 kg/m³, and 5%?
472.5 kg. That is the third card: 0.30 m³ of bed times 1500 times 1.05.
How many 25 kg bags from 567 kg?
23 bags on the bags page, because 567 / 25 = 22.68, rounded up.
What waste should I add for mortar?
Usually 5-10%. An uneven base and work breaks sit nearer 10%. Bags still round up.
Where is cement from this volume?
On cement in mortar. 1.00 m³ at 350 kg/m³ and 5% is 367.50 kg, 15 bags of 25 kg.
Should I type 15 mm as 0.015?
Read the field label. If it is mm, type 15. If it is meters, 0.015. The wrong scale breaks the mass.
Do empty openings deduct zero?
Empty openings deduct nothing. 50 m² stays 50 until you type 5.
How is this different from tile adhesive?
Adhesive uses kg/m² and a trowel notch. Here a bed times density. Two different materials.
How many m³ are in 567 kg at 1800 kg/m³?
About 0.315 m³ with waste, 0.30 m³ net for a 15 mm bed on 20 m².
Knowledge sources
Volume and waste come from the sizes you type. Below are volume and NIST SI units.
Page updated in 2026.