How Surfacely calculates hours and materials
Every surface in Surfacely produces a calculated area, a labour hour estimate, and a material volume. You can see the exact formula behind any of these — no black-box numbers, no guessing.
Opening the formula sheet
In the scoping view, each surface block has a small ƒ button. Tap it to open the Calculation breakdown — a panel showing:
- Area — the geometry formula and the inputs used (length, width, quantity, girth, pitch multiplier, etc.)
- Hours — how area, production rate, coats and the prep rate combine into labour hours
- Material — how area, spread rate, coats, and container sizes produce the volume to buy
You can also reach this from inside the measurement view — the link How is this calculated? opens the same breakdown.
Area calculation
Area starts from your measurements and the surface type's geometry rule:
- Walls: height × length × quantity
- Ceilings: length × width × quantity
- Roofs: length × width × quantity × pitch multiplier (1.0–1.5)
- Gutter / fascia / skirting / soffit: length × girth × quantity
- Windows and doors: component-based — window sashes (the bars around each pane), frames, sills, reveals, architraves; woodwork only, no glass area included
- Balustrades: height, run length, and component toggles combined via the balustrade formula
If you entered an area directly from plans, that figure passes through unchanged.
Hours calculation
Painting hours = area ÷ production rate × coats
Prep hours = area ÷ prep rate, added on top. There is no coats term: you prep a wall once, before the first coat, so the prep hours are the same at one coat or three. There is no speed term either — prep depends on the condition of the surface, so changing the speed step or switching to spray leaves it untouched.
- Production rate — the m²/hr figure for this surface's speed step
- Coats — the number of paint coats (0 means wash only on external areas)
- Prep rate — how much surface each level preps in an hour: Minimal 75 m²/hr (800 ft²/hr), Light 52.5 (565), Sound 35 (375), Standard 25 (270), Moderate 16 (170), Heavy 10.5 (115), Very Heavy 6.5 (70), with Extensive 4 (43), Strip Back 2.5 (27), Strip & Rebuild 1.5 (16) and Restoration 1 (11) for major-repair and heritage work. A slower rate means more prep. None adds no prep hours at all. Prep depends on the condition of the surface alone — the painting speed and method never change it.
- Method — brush/roll or spray changes nothing in the formula. The speed step and the spread rate are the ones you chose on the surface; choosing spray only marks the steps that are typical for it (Open, Rapid and High-volume for speed, one step below the surface's default for spread rate), so you can see them without anything moving on its own
Material calculation
Material volume = area × coats ÷ spread rate, then rounded up to whole containers at the buy size configured for that category.
The spread rate is the one chosen on this surface while measuring. If none was chosen, it is the spread rate set on the surface's paint in Materials — and if that paint is set to "Depends on the surface", the surface's own rate. You can override the cost per L at the quote level without touching your global catalogue.
Why it matters: the formula sheet is your first stop when a surface looks wrong. Before adjusting anything, tap ƒ — most unexpected hour counts come from a mistyped dimension or a coats setting left at the default. The formula shows the cause in seconds.