Use the shape the model actually supports.
Main area = length × (first width + last width) ÷2. This is a trapezoid with parallel end widths and a straight, linear widening or narrowing. For a rectangle, both widths are equal.
Separate apron area = apron length × apron width. Add it only when it does not overlap the main section. Curved edges, islands or more complex outlines need another measurement; this two-section model cannot infer them.
Separate cleaned area from boundary scope.
Total supported area × your chosen cleaning rate, plus your condition adjustment, customer travel and separately agreed edge/scope charge, produces the subtotal. The minimum applies afterwards.
Extra edge/detail time is an internal labour input. It is not automatically the same as the separate customer charge. Neither field estimates sealing, repairs, resurfacing or material quantities.
Why this is a separate tool from the general surface calculator.
The pressure-washing tool begins with one rectangle. This page measures a widening main section and a separate apron, rejects half-entered apron dimensions, and records edge time separately from on-site time.
For two equal-area scenarios, an entered 0.5 extra edge hour at one worker and£25/hour changes costs by £12.50. That is a declared difference in your work assumption, not a claim that all driveways require that allowance.
Measure before using the worksheet.
Use the sketch and dimension definitions below to check the two sections. With scripts disabled, enter the GBP/metres values as a manual worksheet and work through the area and price formula. Do not add overlapping shapes.
Illustrative arithmetic / not market rates
One widening run and a separate apron
Main length12m; parallel widths3m and5m. Apron3m ×4m beyond the main boundary. Rate£4/m²; separate scope£20; no condition/travel uplift.
Declared scenario
EXAMPLE ONLY- Main area:12 ×(3+5) ÷2
- 48m²
- Separate apron:3 ×4
- 12m²
- Combined area
- 60m²
- Area charge + separate scope
- £260.00
- 3 on-site +0.5 edge +0.5 setup +1 travel hour
- 5 hours
- 5 ×1 worker ×£25 +£40 other costs
- £165.00
Profit on these inputs is £95, with36.54% margin. The same 60m² without the separate0.5 edge hour has£152.50 costs. The sketch is illustrative geometry, not a site survey or treatment plan.
Scenario record checked . Read the formula and scenario register.
Review the assumptions
A checklist for this page
- Confirm straight sides and parallel measured end widths.
- Exclude any overlap between main section and apron.
- Record edge/detail time separately only if not already included.
- Keep sealing, replacement and public pavement outside the chosen cleaning scope.
Driveway pricing: questions
Can this measure a curved driveway automatically?
No. The main section assumes linear widening/narrowing. Use a separately justified area measurement for curves or islands; do not force them into this trapezoid.
What if there is no apron?
Leave both apron dimensions at zero. One nonzero dimension with the other zero is rejected because it is incomplete.
Are paving, road and garden included?
Only the cleaning boundaries you measured. The model does not identify a property boundary, ownership or service availability.
Does the estimate include sealing or re-sanding?
There is no sealing or product-coverage model here. Define any independently agreed scope separately rather than assuming it follows from area.
Sources and evidence limits
- WashTally formula and scenario register v1.0.0
Declared arithmetic and explicitly hypothetical scenarios checked by automated tests. No trade certification or representative market rates.
Record checked: - NIST: international-foot conversion
1 international foot = 0.3048 metre exactly; square-unit conversion is the square of the length factor. This does not convert currency or market prices.
Record checked:
A source record or passing arithmetic test does not establish a universal rate, professional review, property assessment or guaranteed outcome.