Example 1
- 0.3 m³, 1600 kg/m³
- bag 25 kg, +5% waste
504 kg → 21 bags
How many bags for 0.30 m³? 1600 kg/m³ × 5% ÷ 25 kg → 21 bags (504 kg).
Mortar Bags Calculator
Enter the volume you need and the bag size. The calculator multiplies m³ by density and waste, then divides by the pack and rounds up. 0.3 m³ at 1600 kg/m³, 5%, and 25 kg is 504 kg, 21 bags. 1 m³ at 1800 kg/m³, 10%, and 30 kg is 1980 kg, 66 bags.
Results
Volume needed, Mix type, Bag size (kg) and Custom density (kg/m³). The result shows up here.
Bag estimate from volume. Related: mortar requirement, cement in mortar.
How the results are calculated
V0.3 m³
ρ1600
Bag25 kg
Bags21
The mortar bags calculator turns volume into packs. Mass is volume × density × (1 + waste/100). Bags are mass divided by bag size, rounded up. Optional water is liters per bag × bag count.
A small repair of 0.3 m³ at 1600 kg/m³, a 25 kg bag, and 5% is 504 kg and 21 bags. A full meter at 1800 kg/m³, 30 kg, and 10% is 1980 kg and 66 bags. A thin 0.15 m³ at 1500 kg/m³, 20 kg, and 0% is 225 kg and 12 bags.
Enter volume needed in m³ and bag size in kg. Mix type, custom density, waste, water per bag, and price are optional. A comma in 0.3 works the same as a period. Take volume from mortar requirement or from concrete.
Cement in a 1 m³ mix at 350 kg/m³ belongs on the cement-in-mortar page: 367.50 kg at 5%. A 15 mm bed on 20 m² is 567 kg on mortar requirement; at 25 kg that is 23 bags.
A fraction of a bag goes up. 20.16 bags is 21, not 20. A dry bag and tap water are two entries: water per bag does not change bag count, it only shows liters.
Enter 0.3 m³ at 1600 kg/m³, 25 kg, and 5%: 504 kg and 21 bags. Then 1 m³ at 1800 kg/m³, 30 kg, and 10%: 66 bags.
How to use this calculator
- Enter volume needed in m³, for example 0.3 from a small repair or 1 from a full meter.
- Pick a mix type or a custom density in kg/m³ and a bag size, for example 25 kg.
- Add waste, usually 5–10%. Water per bag is optional.
- Click Calculate. 0.3 m³, 1600 kg/m³, 5%, and 25 kg give 504 kg, 21 bags.
- Bed mass belongs on mortar requirement. This calculator stays bags.
Formula
mass = volume × density × (1 + waste/100)
bags = ⌈mass ÷ bag_size⌉
0.3 m³ at 1600 kg/m³, 5%, and 25 kg: mass = 504 kg, bags = 21. 1 m³ at 1800 kg/m³, 10%, and 30 kg is 66 bags.
Volume and bags
Volume × density × (1 + waste), then bag size rounded up. 0.3 m³ at 1600 kg/m³, 5%, and 25 kg is 504 kg, 21 bags.
- m³
- Volume of mix you need. 0.3 m³ at 1600 kg/m³ and 5% is 504 kg. 1 m³ at 1800 kg/m³ and 10% is 1980 kg, 66 bags of 30 kg.
- kg/m³
- Density from the mix list or the custom field. Standard 1600 on 0.3 m³ plus 5% is 21 bags of 25 kg.
- kg
- Bag size. 504 ÷ 25 = 20.16 → 21. 1980 ÷ 30 = 66.
- ceil
- Round up. You cannot buy a fraction of a bag, so 20.16 becomes 21.
Usage examples
Example 2
- 1 m³, 1800 kg/m³
- bag 30 kg, +10% waste
1980 kg → 66 bags
1 m³ at 1800 kg/m³ × 10% ÷ 30 kg → 66 bags (1980 kg).
Example 3
- 0.15 m³, 1500 kg/m³
- bag 20 kg, 0% waste
225 kg → 12 bags
0.15 m³ at 1500 kg/m³ ÷ 20 kg → 12 bags (no waste).
Example 4
- 0.315 m³
- 1800 kg/m³
- 25 kg bag, no waste
567 kg → 23 bags
0.315 × 1800 ÷ 25 = 22.68 → 23. That mass comes from the neighboring mortar page.
Example 5
- 0.5 m³
- 1600 kg/m³
- 25 kg bag, +5%
840 kg → 34 bags
0.5 × 1600 × 1.05 ÷ 25 = 33.6 → 34. A larger purchase at the same density.
Example 6
- 0.3 m³
- 1600 kg/m³
- 25 kg bag, no waste
480 kg → 20 bags
0.3 × 1600 ÷ 25 = 19.2 → 20. The same volume with 5% is 21 bags.
Related calculators
Frequently asked questions
How do I calculate mortar bags from volume and density?
Multiply m³ by kg/m³ and by (1 + waste/100), divide by bag size, and round up. 0.30 m³ × 1600 × 1.05 ÷ 25 → 21 bags.
How many bags do I need for 0.30 m³ at 1600 kg/m³, 5%, and a 25 kg bag?
21 bags. Mass 504 kg. 1 m³ at 1800 kg/m³, 10%, and a 30 kg bag is 66 bags.
How is this different from bed-mass mortar, cement dosage, or concrete bags?
Here the result is premixed mortar bag count from m³ and kg/m³. Bed mass from mm, cement-only dosage, and concrete bags live on sibling cards.
How is bag count calculated?
The calculator multiplies volume by density and by (1 + waste/100), divides by bag size, and rounds up. 0.3 m³ at 1600 kg/m³, 5%, and 25 kg is 504 kg and 21 bags.
Which unit should I use for volume?
Cubic meters in metric. 0.3 m³ at 1600 kg/m³ and 5% is 504 kg. In US units the field shows cubic feet.
What waste should I add?
Usually 5–10%. At 0.3 m³, 1600 kg/m³, and a 25 kg bag, 5% waste lifts the result from 20 to 21 bags. The calculator still rounds a fraction up.
What does mix type do?
It sets density: lightweight ≈ 1400, standard ≈ 1600, cement-lime ≈ 1800, heavy ≈ 2000 kg/m³. A custom density overrides the type.
Does water change the bag count?
No. The water field is liters per bag. The calculator multiplies that by bag count. Bags follow dry mass and pack size only.
How is this different from mortar requirement?
Here the input is volume and the result is bags. Mortar requirement finds volume and mass from area and bed thickness. 567 kg in 25 kg bags is 23 bags.
Where do I count cement in the mix?
On the cement-in-mortar page. 1 m³ at 350 kg cement/m³ and 5% is 367.50 kg of cement. Here you count whole mortar bags, not cement alone.
Does a comma in 0.3 work?
Yes. A comma and a period are the same volume. At 0.3 m³, 1600 kg/m³, 5%, and 25 kg the result stays 21 bags.
What is the primary result?
Bag count after rounding up, for example 21 at 0.3 m³. Mass 504 kg appears beside it. Water and cost are optional.
Does the result replace a datasheet?
No. The calculator is a purchase estimate. Bag density and manufacturer guidance may need an adjustment.
Is this a free mortar bags calculator?
Yes. Enter volume, kg/m³, and bag size and you see the bag count at once. No account required.
Knowledge sources
Mass is volume × density. Bag count is mass divided by pack size, rounded up. Mass and volume units below from NIST.
Page updated October 12, 2026.