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Measurements

Roof Layout Studio calculates measurements from traced geometry, the project scale, and assigned pitches. This page explains what is measured, how the values are computed, and how to read them in the editor and the report.

Units

Units are set globally in Settings (see Settings). Two systems are supported:

  • Imperial — feet and inches for lengths; square feet for areas
  • Metric — meters and centimeters for lengths; square meters for areas

Switching units re-labels the UI. The underlying data doesn't change — only the display.

Edge lengths

Every classified edge has a real-world length based on:

  • its pixel length on the plan
  • the project scale (see Set Scale)
  • its slope factor — how much its 3D length differs from the 2D plan projection (for hips, valleys, rakes on sloped surfaces)

Slope factor

A hip or valley running diagonally across a sloped roof is longer in reality than on the flat plan because it traverses both horizontal and vertical distance.

The slope factor is computed automatically from the pitch and slope direction of the adjacent facets. Edges that belong to two pitched facets (typical hips and valleys) use both pitches in the formula.

INFO

Eaves and ridges are horizontal, so their slope factor is always 1 — their plan length equals their real length.

Facet areas

Each facet has two area values:

  • Flat area — the polygon area on the plan, converted via scale
  • Real area — the flat area adjusted for pitch (what shingles cover)

How real area is computed

real_area = flat_area * slope_factor(pitch)

For a pitch of 6/12:

slope_factor = sqrt(1 + (6/12)^2) = sqrt(1.25) ≈ 1.118
real_area ≈ flat_area * 1.118

A 100 sq ft flat area becomes ~111.8 sq ft at 6/12 pitch — and that is the shingle coverage value.

Facets with holes

If a facet has inner closed loops on the same layer, their areas are subtracted from its area automatically — with or without Delete facet. The difference:

  • Inner loop exists as a separate facet (default after drawing) — outer area = outer − inner, plus the inner is counted as its own facet. Total sum equals the full outer area.
  • Inner facet deleted with Delete facet — outer area = outer − inner, and nothing else is added. This is the correct state for skylights, chimneys, vents.

See Edges and facets → Facets with holes.

Reading values on the canvas

Every facet shows its label near the center:

  • top line: area (real with pitch if set, or flat if pitch is 0 / unset)
  • bottom line: pitch (e.g., 6/12)
  • small arrow: slope direction (if a slope is defined)

Facet with area, pitch, and slope direction labels

If any value is missing (for example, pitch isn't set), only available values are shown.

Totals in the report

The generated report groups measurements as totals:

  • Total facet area — sum of all real areas
  • Edge totals by type — total eaves length, total ridges, total hips, total valleys, and so on

See Report for the exact layout.

Tips

  • Always set scale first. Without scale, areas and lengths are unusable.
  • Set pitch for every facet before checking area totals.
  • Classify every edge before expecting correct totals — unspecified edges don't contribute to the report's type totals.
  • When comparing with a customer's measurements, double-check units in Settings.

Common issues

Area value looks off

  • Scale is incorrect. Redo Set Scale using a longer or more verified reference.
  • Pitch is wrong. Verify the pitch is applied correctly.

Edge length doesn't match the plan

  • The edge's slope factor depends on the neighboring facet pitches. Make sure both facets on either side of the edge have pitch set.
  • For single-facet edges (eaves, rakes), only that facet's pitch is used.

Real and flat areas are the same

  • Pitch is 0/12. The facet is treated as flat.