Example 1
- 1.00 m³ × 350 kg/m³
- +5% waste
- 25 kg/bag, $20
367.50 kg → 15 bags
A quick estimate of cement mass for a standard 1:4 mix with a modest contingency.
Amount of cement in mortar calculator
Type mortar volume and kilograms of cement per m³. The calculator multiplies them by waste and divides by bag size. One m³ at 350 kg/m³ and 5% is 367.50 kg, 15 bags of 25 kg. Half a meter at 430 kg/m³ with no waste is 215 kg, 9 bags. Two m³ at 250 kg/m³ and 10% is 550 kg, 11 bags of 50 kg.
Also useful: mortar requirement, mortar bags needed.
Results
Mortar volume, Mix ratio (cement:sand), Cement per m³ (kg) and Waste %. The result shows up here.
How the results are calculated
Cement in mortar counts cement alone, not the whole mix. The formula is volume times kg/m³ times (1 plus waste). Bags are ceil(cement divided by bag size). The cement:sand ratio is a hint toward kg/m³; the result still follows the cement-per-m³ field.
A full meter at 350 kg/m³ and 5% is 367.50 kg and 15 bags of 25 kg. A richer 0.50 m³ at 430 kg/m³ with no waste is 215 kg and 9 bags of 25 kg. A leaner 2.00 m³ render at 250 kg/m³ and 10% is 550 kg and 11 bags of 50 kg. Whole mortar of 0.3 m³ at 1600 kg/m³ is 21 bags on another calculator.
Type mortar volume and cement per m³. Ratio, waste, bag size, and price are optional. An empty bag size leaves kilograms only. A comma in 1.00 works like 1.
Whole mortar mass lives on mortar requirement, mix bags on mortar bags needed. Concrete 2.1 m³ from a slab is not this cement until you type its m³ and recipe.
Cement bags round up. 14.7 bags is 15. Five percent waste on 350 kg is an extra 17.5 kg, often one more bag than dry 350. A 1:3 ratio does not multiply volume by itself: pick kg/m³ from the recipe first.
Type 1.00, 350, 5%, and 25 kg, click Calculate, and match 367.50 kg and 15 bags. Then 0.50 and 430: 215 kg and 9 bags.
How to use this calculator
- Type mortar volume in m³, for example 1.00 or 0.50.
- Enter cement per m³ in kg, for example 350. The cement:sand ratio only hints at the recipe.
- Set waste, usually 5-10%, and bag size, for example 25 kg.
- Click Calculate. 1.00 m³, 350 kg/m³, and 5% give 367.50 kg, 15 bags of 25 kg.
- Whole mortar and mix bags live next door. This calculator stays cement alone.
m³ and kg/m³ for a 25 kg bag
The calculator multiplies mortar volume by cement per cubic meter. 1 m³ at 350 kg/m³ and 5% is 367.50 kg, 15 bags of 25 kg.
- m³
- Mortar volume, first field. 1.00 m³ at 350 kg/m³ and 5% is 367.50 kg of cement, not slab concrete volume.
- kg/m³
- Cement per cubic meter of mix. 350 kg/m³ on 1 m³ plus 5% is 367.50 kg. 430 kg/m³ on 0.50 m³ with no waste is 215 kg.
Usage examples
Example 2
- 0.50 m³ × 430 kg/m³
- 0% waste
- 25 kg/bag, $22
215.00 kg → 9 bags
Richer mixes raise cement mass quickly - bags are usually easier for purchasing.
Example 3
- 2.00 m³ × 250 kg/m³
- +10% waste
- 50 kg/bag, $35
550.00 kg → 11 bags
Shows how waste % and bag size change the purchasing total.
Example 4
- 0.15 m³ × 350 kg/m³
- +5% waste
- 25 kg/bag
55.13 kg → 3 bags
How much cement for 0.15 m³ of 1:4 bricklaying mortar? 55.13 kg , 3 bags.
Example 5
- 0.40 m³ × 430 kg/m³
- +8% waste
- 25 kg/bag
185.76 kg → 8 bags
How much cement for 0.40 m³ of richer 1:3 render mix? 185.76 kg , 8 bags.
Example 6
- 0.80 m³ × 250 kg/m³
- +5% waste
- 25 kg/bag
210.00 kg → 9 bags
How much cement for 0.80 m³ of 1:6 floor screed? 210.00 kg , 9 bags.
Example 7
- 0.05 m³ × 350 kg/m³
- +10% waste
- 25 kg/bag
19.25 kg → 1 bag
How much cement for a 50 L pointing mix at 350 kg/m³? 19.25 kg , 1 bag.
Example 8
- 0.25 m³ × 350 kg/m³
- +8% waste
- 25 kg/bag
94.50 kg → 4 bags
How much cement for 0.25 m³ of pointing mortar at 8% waste? 94.50 kg , 4 bags.
Related calculators
Frequently asked questions
How much cement at 1.00 m³, 350 kg/m³, and 5%?
367.50 kg. With a 25 kg bag that is 15 bags, because 14.7 rounds up.
How many bags at 0.50 m³, 430 kg/m³, and 0%?
9 bags of 25 kg. Mass 215 kg, 215 / 25 = 8.6, rounded up.
How many bags at 2.00 m³, 250 kg/m³, 10%, and 50 kg?
11 bags. Mass is 550 kg, and 550 / 50 = 11 exactly, so ceil does not add a bag.
Does a 1:3 ratio compute kilograms by itself?
No. The result follows cement per m³. The ratio helps you pick 250, 350, or 430.
How many bags of whole mortar at 0.3 m³ and 1600 kg/m³?
21 bags of 25 kg on mortar bags. Here 0.3 m³ at 350 kg/m³ is a smaller cement number.
What waste should I add for cement?
Usually 5%. On 350 kg that is 17.5 kg more and often one extra bag.
Can I buy 14 bags when the result is 14.7?
Round up to 15. The last bag covers a mix that does not come out even.
Where do I get 1.00 m³ of mortar?
From mortar requirement or from the drawing. Type 2.1 m³ of concrete here only when you want cement in that pour.
How is 350 kg/m³ different from 1600 kg/m³?
350 is cement alone. 1600 is whole mortar on the bags page. Two different fields.
How much cement at 1 m³ and 350 kg/m³ with no waste?
350 kg, 14 bags of 25 kg, because 350 / 25 = 14 exactly. Five percent lifts that to 15.
Knowledge sources
Volume and waste come from the sizes you type. Below are volume and NIST SI units.
Page updated in 2026.