CALCULATION MODEL 1.0.0 · UPDATED 17 SEPTEMBER 2026
What these tools estimate
The calculators turn measured geometry into preliminary quantities for bricks, cement, sand, coarse aggregate, plaster and tiles. They help compare options and plan an initial material list. They do not design a structure, certify a mix, create a cutting schedule or account for every site condition.
Units and precision
Lengths are converted to metres before calculation. The exact conversions are 1 mm = 0.001 m, 1 cm = 0.01 m, 1 inch = 0.0254 m and 1 foot = 0.3048 m. Custom concrete volumes also support 1 ft³ = 0.028316846592 m³ and 1 yd³ = 0.764554857984 m³.
Internal values remain unrounded. Display values are shortened for readability. Bricks, tiles and whole cement bags are rounded up only at the order stage. Equivalent bag counts remain fractional so consumption and purchasing are visibly different. Decimal points and single decimal commas are accepted; thousands separators are not.
Planning defaults
| Assumption | Default | Where used |
|---|---|---|
| Cement loose bulk density | 1,440 kg/m³ | Brick, concrete and plaster |
| Sand loose bulk density | 1,600 kg/m³ | Brick, concrete and plaster |
| Aggregate loose bulk density | 1,450 kg/m³ | Concrete |
| Concrete dry-volume factor | 1.54 | Concrete |
| Mortar / plaster dry-volume factor | 1.33 | Brick and plaster |
| Mortar joint | 10 mm | Brick |
| Cement bag | 50 kg | All cement estimates |
| Material waste | 5% | Brick, concrete and plaster |
| Tile waste | 10% | Floor and skirting |
These defaults come from the site’s disclosed preliminary estimating model. They are configurable assumptions, not universal constants or claims that a standards body prescribes these quantities. Dry factors and densities should be replaced by verified supplier or project data when available.
Waste is applied once
Concrete and plaster apply waste to net wet volume before converting it into dry material volumes. Brick calculations apply the allowance separately to the unrounded brick count and the estimated wet mortar volume. Tiles apply waste to the combined unrounded floor and skirting equivalent. In every case, quantities in the material breakdown already include the selected waste.
Limits of each model
Brickwork uses a repeating three-dimensional module. It does not reproduce bond edges, cavities, holes or frogs. Plaster assumes a uniform layer over the net measured area. Concrete uses simple geometry and a loose-volume ratio, excluding water and admixtures. Tiles use area and do not optimize cuts or credit grout-joint coverage. Skirting is an area equivalent.
Validation and changes
The calculation functions are shared by the displayed examples and the browser tools. Automated tests cover known examples, geometry, unit equivalence, waste, rounding and invalid inputs. This is software validation, not independent engineering certification. Changes to formulas or defaults are recorded with a model version and revision date.
Technical references
For project-specific concrete decisions, consult the Concrete Society’s principles of mix design and NRMCA’s pre-construction checklists. They explain the broader mix and ordering considerations; they are not cited as endorsements of this calculator’s dry factors.
Report a reproducible discrepancy through the contact form. Include the calculator, all inputs and units, and the result you expected. Do not send confidential project documents.