Example 1 — Standard mix
- 0.3 m³, 1600 kg/m³
- bag 25 kg, +5% waste
504 kg → 21 bags
This is a practical purchasing scenario because bag count usually matters more than an intermediate result in kilograms or litres.
Mortar bags needed calculator
Bag count and mixing water from volume, mix density, bag size and waste %.
Also useful: concrete volume, cement in mortar.
Results
Enter data and click Calculate.
How the results are calculated
Mass = volume × density × (1 + waste/100). Bags = ceil(mass ÷ bag size). Water = mass × water ratio.
How to use this calculator
- Enter the mortar volume needed.
- Pick a mix density type.
- Enter bag size (weight of one bag) — required for the calculation.
- Optionally under Additional options: custom density, waste %, water and price.
- Calculate to see bag count and optional water/cost.
Usage examples
Example 2 — Cement-lime, larger job
- 1 m³, 1800 kg/m³
- bag 30 kg, +10% waste
1980 kg → 66 bags
After adding reserve, the result reflects real working conditions better and reduces the risk of interrupting the job.
Example 3 — Lightweight, small job
- 0.15 m³, 1500 kg/m³
- bag 20 kg, 0% waste
225 kg → 12 bags
For larger work scopes, converting the result into bags makes logistics, cost, and delivery planning easier.
Frequently asked questions
How is the number of bags calculated?
Mass (kg) = volume (m³) × mix density × (1 + waste%); bags = ceil(mass ÷ bag size).
How much water do I need?
Water (L) = mass (kg) × water ratio (L per kg) from the bag instructions, typically 0.16–0.20 L/kg.
Which mix density should I pick?
Dry bagged mortars are typically 1400–2000 kg/m³ depending on type — check the bag label for exact figures.
Why round bags up?
You cannot buy a fraction of a sealed bag, so any remainder rounds up to a full bag.
What waste % is typical for bagged mortar?
Usually 5–10% to cover spillage, mixing losses and tool cleaning.
How do I switch metric ↔ US units?
Use the units selector in the header. Field labels, results and examples update automatically when you switch metric ↔ US.
Why is a bag calculator more practical than a weight-only result?
Because purchasing and transport are usually organized around full bags, not abstract weight values.
Should the result always be rounded up?
For buying, most often yes, because you do not purchase a fraction of a bag and a small reserve is usually safer than running short.