Example 1
- thickness 15 mm
- 1800 kg/m³, +5% waste
567 kg
How much mortar for 20 m²? 15 mm × 1800 kg/m³ × 5% → 567 kg (0.315 m³).
Mortar Calculator
Enter area, bed thickness, and density. The calculator finds volume from net area and multiplies by density and waste. A 15 mm bed on 20 m² at 1800 kg/m³ and 5% is 567 kg. A 50 m² wall minus 5 m² at 10 mm, 1600 kg/m³, and 10% is 792 kg.
Results
Enter area, layer thickness, openings, and mortar type. The result shows up here.
The calculator estimates mortar bed volume and mass. Related: cement in mortar, mortar bags.
How the results are calculated
Net20 m²
Bed15 mm
ρ1800
Mass567 kg
The mortar calculator finds bed volume and mass. The formula is V = (area − openings) × (thickness_mm ÷ 1000) × (1 + waste/100), and mass = V × density.
A 20 m² wall at 15 mm, 1800 kg/m³, and 5% is 0.315 m³ and 567 kg. A 50 m² wall minus 5 m² at 10 mm, 1600 kg/m³, and 10% is 792 kg. A 15 m² floor at 20 mm, 1500 kg/m³, and 5% is 472.5 kg.
Enter area and thickness in millimeters. Openings, type, custom density, and waste are optional. Type sets density; custom density overrides it. A comma in 15.0 works the same as a period.
Cement from that volume is calculated on the cement-in-mortar page. Bag counts are on the mortar-bags page. Tile adhesive uses kg/m², not masonry bed thickness.
Without waste the same 20 m² and 15 mm at 1800 kg/m³ is 540 kg. Five percent lifts the result to 567 kg. 567 kg in 25 kg bags is 23 bags on the neighboring page.
Enter 20, 15 mm, 1800, and 5%: 567 kg. Then 50 minus 5, 10 mm, 1600, and 10%: 792 kg.
How to use this calculator
- Enter area in m², for example 20 or 50, and subtract openings when present.
- Enter bed thickness in millimeters. 15 mm on 20 m² at 1800 kg/m³ is 567 kg with 5%.
- Pick mortar type or enter 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, 1600, and 10% is 792 kg.
- Bag counts and cement are on the related pages. This page gives mortar volume and mass.
Formula
net = max(0, area − openings)
V = net × (thickness_mm ÷ 1000) × (1 + waste/100)
mass = V × density
A 20 m² wall at 15 mm, 1800 kg/m³, and 5%: V = 0.315 m³, mass = 567 kg. A 50 − 5 m² wall at 10 mm, 1600, and 10% is 792 kg.
Bed and density
Net area × thickness × (1 + waste) × density. A 15 mm bed on 20 m² at 1800 kg/m³ and 5% is 567 kg (0.315 m³).
- mm
- Bed thickness. 15 mm = 0.015 m. On 20 m² at 1800 and 5% that is 567 kg.
- kg/m³
- Density. 1800 on 0.315 m³ is 567 kg. 1600 on 45 m² net at 10 mm and 10% is 792 kg.
- m²
- Net area. 20 m² at 15 mm, 1800, and 5% is 567 kg. 50 − 5 m² at 10 mm, 1600, and 10% is 792 kg.
- V
- Volume with waste. 0.315 m³ on the first example; mass = V × ρ.
Usage examples
Example 2
- 50 m² − 5 m² openings
- 10 mm, 1600 kg/m³, +10%
792 kg
A 50−5 m² wall at 10 mm, 1600 kg/m³ and 10% → 792 kg.
Example 3
- 15 m² × 20 mm
- 1500 kg/m³, +5%
472.5 kg
15 m² × 20 mm × 1500 kg/m³ × 5% → 472.5 kg.
Example 4
- 30 m²
- 12 mm
- 1800 kg/m³
- +8% waste
699.84 kg · 0.389 m³
30 × 0.012 × 1.08 × 1800 = 699.84. Eight percent waste for unevenness.
Example 5
- 20 m²
- 15 mm
- 1800 kg/m³
- no waste
540 kg · 0.300 m³
20 × 0.015 × 1800 = 540. The same wall with 5% is 567 kg.
Example 6
- 20 m²
- 15 mm
- heavy ~2000 kg/m³
- +5%
630 kg · 0.315 m³
20 × 0.015 × 1.05 × 2000 = 630. Denser mortar on the same bed.
Related calculators
Frequently asked questions
How do I calculate mortar from area and bed thickness?
Subtract openings, multiply by thickness in meters (mm ÷ 1000) and by (1 + waste/100), then by density. 20 m² × 0.015 × 1.05 × 1800 → 567 kg.
How many kg do I need for 20 m² at 15 mm, 1800 kg/m³, and 5%?
567 kg, or 0.315 m³ with waste. A 50 m² wall minus 5 m² at 10 mm, 1600 kg/m³, and 10% is 792 kg.
How is this different from thinset or a cement–sand mix ratio?
Here the result is bed volume and mass from density. Thinset uses kg/m² and a trowel notch. Cement–sand ratios and bag-only counts live on sibling cards.
How is mortar amount calculated?
The calculator subtracts openings from area, multiplies by thickness in meters (mm ÷ 1000) and by (1 + waste/100), then by density. A 20 m² wall at 15 mm, 1800 kg/m³, and 5% is 0.315 m³ and 567 kg.
Which unit should I use for thickness?
Millimeters in the thickness field. 15 mm becomes 0.015 m in the formula. Entering 15 as meters would inflate the mass a thousandfold.
What waste should I add?
Usually 5–10%. An uneven substrate is closer to 10%. At 20 m², 15 mm, and 1800 kg/m³, 5% waste lifts mass from 540 kg to 567 kg.
What does mortar type do?
It sets density: cement-lime ≈ 1800, cement ≈ 1600, lightweight ≈ 1500, heavy ≈ 2000 kg/m³. A custom density overrides the type.
How are openings subtracted?
From area before multiplying by thickness. 50 m² minus 5 m² at 10 mm, 1600 kg/m³, and 10% is 792 kg. An empty field means zero.
How is this different from tile adhesive?
Here the result is volume and mass from bed × density. Adhesive uses kg/m² and a trowel notch. They are different materials.
Where do I count bags and cement?
Bags on the mortar-bags page: 567 kg in 25 kg bags is 23 bags. Cement in mortar counts cement kilograms from volume.
Does a comma in 15.0 work?
Yes. A comma and a period are the same thickness. At 20 m², 1800 kg/m³, and 5% the result stays 567 kg.
What is the primary result?
Bed volume with waste, for example 0.315 m³ at 20 m² and 15 mm with 5%. Mass 567 kg appears beside it after density.
Does the result replace a datasheet?
No. The calculator is a purchase estimate. The manufacturer and substrate may need a different density or thickness.
Is this a free mortar calculator?
Yes. Enter area, thickness in mm, and density and you see kilograms at once. No account required.
Knowledge sources
Bed volume is area × thickness. Density comes from mortar type or the datasheet. Mass and volume units below come from NIST.
Page updated October 12, 2026.