A correct number with the wrong unit still makes a bad estimate. Calculate project geometry first, then convert it into the quantity or package size actually sold.
Use wet yield for bagged concrete
Bag mass is not finished volume. The bag tool takes required cubic metres and the manufacturer’s wet yield in litres per bag. One cubic metre is 1,000 litres. Apply the waste fraction before dividing by yield and rounding upward to whole bags.
Include gaps and openings in the model
Brick modules include the face dimensions plus mortar joints. Openings reduce a flat wall’s area, while corners, bonds and cuts add complexity. A deck layout depends on board face width and gaps, not just total board area. Choose the geometry that matches the task.
Separate quantity from design
Waste is an entered planning assumption, not a structural or product standard. Verify measurements, wet yield, package size and delivery minimums. Strength, reinforcement, fixings, suitability and local construction rules are outside the quantity result. Keep a measured drawing beside the exported estimate.
Worked example
Scroll the table horizontally on small screens to see every column.
| Required volume | Waste | Wet yield | Bags |
|---|---|---|---|
| 0.5 m³ | 10% | 10 litres/bag | 55 |
0.5 × 1,000 × 1.10 / 10 = 55. Use yield stated for the actual product.
Sources and checks
Examples are illustrative and can be checked with the linked tools. Read each tool’s assumptions before applying its result. How we verify methods.