How PatioBoQ calculates quantities and reviews quotes.
The calculator uses deterministic arithmetic. The paid pilot uses human review of the written quote. Neither can replace a site survey or a project-specific construction design.
The calculation chain
| Quantity | Formula |
|---|---|
| Net area | Sum of non-overlapping rectangle areas, minus specified cutouts |
| Paver order area | Net area × (1 + paver waste percentage / 100) |
| Compacted base volume | Net area × compacted base thickness |
| Bedding volume | Net area × bedding thickness |
| Bank excavation | Net area × total layer thickness, under the stated level assumption |
| Loose spoil volume | Bank excavation × soil swell factor |
| Theoretical base mass | Compacted base volume × selected compacted density |
The engine converts inputs to metres before calculating and rounds only the displayed results. A foot is exactly 0.3048 m, an inch is 0.0254 m, and a cubic yard is 0.764554857984 m³. These use the international foot, not the obsolete US survey foot.
Reference: NIST SI conversion factors.
Worked example: a 20 × 14 ft patio
This is an estimating example, not a recommended construction design. It assumes 60 mm pavers, 25 mm bedding, 150 mm compacted base, 10% paver waste and a 1.25 spoil swell factor. Finished and existing ground levels are assumed equal.
| Quantity | US units | Metric units |
|---|---|---|
| Net patio area | 280.00 sq ft | 26.01 m² |
| Paver order, 10% allowance | 308.00 sq ft | 28.61 m² |
| Compacted base | 5.10 cu yd | 3.90 m³ |
| Bedding sand | 0.85 cu yd | 0.65 m³ |
| Bank excavation | 8.00 cu yd | 6.11 m³ |
| Loose spoil, 1.25× | 9.99 cu yd | 7.64 m³ |
Displayed quantities are rounded to two decimals. Confirm material specifications and delivery units with your supplier before ordering.
What the defaults do not establish
The default 150 mm base, 25 mm bedding, 60 mm pavers, 10% waste, 1.25 soil swell and 2.0 tonnes/m³ base density are editable estimating examples. They do not establish appropriate depth, drainage, structural capacity, material compatibility or regulatory compliance for your property.
The excavation estimate assumes the finished surface matches the existing ground level. It does not include demolition, base extension, overdig, slope changes, unsuitable soil replacement or underground obstructions. Aggregate ordering needs a supplier conversion; disposal needs separate material and weight checks.
Multiple rectangle dimensions alone do not define shared edges. The engine therefore does not give a certain perimeter for multi-part geometry or cutouts. Measure exposed edging from a plan.
How the quote review works
- You provide dimensions, project scope and a written quote.
- An operator checks readability and whether the project fits the pilot before offering payment.
- A reviewer records the original text and page number for supported claims.
- Scope status and quantity comparison status are assessed separately.
- You receive clarification questions in your private project workspace.
The pilot does not use automated OCR or an AI system to decide whether the contractor’s price is fair. When evidence is insufficient, the appropriate result is a question or an “insufficient data” status, not a fabricated conclusion. See the synthetic example report.
Construction context and corrections
CMHA’s construction guidance describes separate tasks such as subgrade preparation, base placement, bedding and edge restraints. The applicable project specification and manufacturer’s instructions still govern the selected system. A checklist category is not a universal requirement to add that item on every job.
Found a calculation or wording problem? Contact PatioBoQ with the input values and the page URL. For a private report, include the project ID but not its access key. We can issue a revised report when a verified correction is needed.