Mosquito dunks are dosed by water surface area, not volume — depth is irrelevant. The surface area drives a single count.

area (sq ft):
  rectangle  = length × width
  circle     = π × (diameter / 2)²
  direct     = entered surface area

dunks per site:
  area ≤ 5 sq ft        → ¼ dunk      (discrete label breakpoint)
  5 < area ≤ 25 sq ft   → ½ dunk
  25 < area ≤ 100 sq ft → 1 dunk
  area > 100 sq ft      → ceil(area / 100)   (1 dunk / 100 sq ft)

total dunks  = dunks per site × number of sites

season supply (optional):
  replacements = ceil(season days / 30)      (replace every ~30 days)
  season dunks = total dunks × replacements

Bits granular equivalent (advisory — re-verify):
  tbsp = ceil(area / 75)

Below 100 sq ft the dose is a discrete breakpoint lookup, not the ÷100 rule — a 3 sq ft birdbath takes ¼ dunk, not a wasteful whole one. Above 100 sq ft it is the headline rate, rounded up so the whole surface is covered. One dunk is roughly a 10 ft × 10 ft patch — about a parking space.

The 30-day cadence is a supply count, not a scheduled appointment — replace a dunk sooner if it has dissolved away or after heavy rain.

The Bits granular rate (1 tbsp / 75 sq ft) and the 4× high-organic-water note are flagged advisories: their label PDFs were not machine-readable at build time, so re-verify them against the EPA-registered label before relying on them. We do not encode the unverified large-area Bits figures.

Sources: Summit Responsible Solutions — Mosquito Dunks (headline rate, fractional guidance, 30-day cadence, Bti active ingredient); IERE — How to Use Mosquito Dunks (duration, reapply after rain); EPA Mosquito Dunks label PPLS 006218-00087 (fractional breakpoint table).