Example 1 — 1 m³ at 1:4
- 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
Cement mass and bags from mortar volume, mix ratio (kg cement per m³) and waste %.
Also useful: mortar requirement, mortar bags needed.
Results
Enter data and click Calculate.
How the results are calculated
Cement = volume × kg/m³ × (1 + waste/100). Bags = ceil(cement ÷ bag size).
How to use this calculator
- Enter mortar volume (volume unit from the header).
- Pick a mix ratio (e.g. 1:4) or enter a custom dosage in kg/m³ (SI).
- Set waste %, bag size and price.
- Calculate to see cement mass, bags and cost.
Usage examples
Example 2 — 0.5 m³ at 1:3
- 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 m³ at 1:6
- 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.
Frequently asked questions
How is cement mass calculated?
Cement (kg) = volume (m³) × kg cement per m³ (from ratio) × (1 + waste%). Example: 1 m³ at 1:4 (~350 kg/m³), +5% → 367.5 kg.
What do the mix ratios mean?
Cement:sand by volume — richer 1:3 mixes use more cement per m³ than lean 1:6 mixes.
Can I override the cement dosage?
Yes, the kg-per-m³ field is editable and takes priority over the ratio preset.
How many bags do I need?
Bags = ceil(cement kg ÷ bag size). A fraction of a bag still counts as a full bag.
Is this cement or ready mortar?
This is cement content within a mortar mix — use the mortar requirement calculator for total mortar mass.
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 kilogram result not always enough?
Because cement is usually bought in bags, not in a laboratory-precise kilogram amount.
What should I check after calculating cement?
Most often cost, bag count, and whether the assumptions match the actual construction method you want to use.