Two interchangeable input modes feed one shared spots → grams → tubes back-end. Pick the mode that matches how you measured — the tool never averages the two.

Mode A (linear feet):
  spots          = ceil( (linear_ft / 10) × spots_per_10ft )
  gel_used       = spots × grams_per_spot

Mode B (floor area):
  gel_used       = (area_sqft / 9) × grams_per_9sqft_effective
  implied_spots  = round( gel_used / grams_per_spot )   // cross-check only

Both modes:
  gel_with_buffer = gel_used × (1 + waste_pct)
  tubes_needed    = ceil( gel_with_buffer / tube_size )

Severity rate map (Mode A, spots per 10 ft): light = 2, moderate = 2, heavy = 4. Cockroach Facts gives one band for light/moderate (1–3) and one for heavy (3–5), so light and moderate share the same midpoint.

Area gram rate (Mode B, grams per 9 sq ft): light = 1.5, moderate = 2.25, heavy = 3.0, then × 1.0 for small species or × 1.5 for large. The single cited anchor is Better Termite's 3 g per 9 sq ft for a heavy job; the lighter-severity and species scalars are derived defaults, surfaced as editable overrides — not cited manufacturer specs.

Constants (all editable under Advanced): 0.5 g per spot (pea-sized; PCT band ¼–½ g), 30 g per tube (Advion / label-typical low end of 30–35 g), 10% waste buffer. Grams-per-spot above 0.5 g still computes but flags the bait-aversion caution rather than blocking. The tube count rounds up on the un-rounded grams-with-buffer, so a buffer landing exactly on a tube boundary (e.g. 30.0 g) is one tube, not two.

Sources: Cockroach Facts (0.5 g/spot, spots-per-10-ft bands, bait-aversion); PCT — Pest Control Technology (¼–½ g spot weight, species-banded placements per sq yd, 3–4 in from harborage); Better Termite (3 g per 9 sq ft, 30–35 g tube size).