Feeding Transition Calculator — Implementation Guide (30 kg adult)

1) Purpose & principle

The calculator keeps energy intake continuous while transitioning from kibble (current) to gently cooked (GC, target).
Internally it uses the kibble chart’s month-level precision; externally it communicates in GC phases (<5 mo, 5–6 mo, 7–12 mo).

Dog profile: 30 kg adult only.
Supported ages: 2.0 to 12.0 months inclusive.
If the user enters a value outside this range, clamp to the nearest bound and show a subtle note.
Required configuration at runtime: kibble energy density (kcal per 100 g).
If missing, show an error and do not compute.

Kibble reference points (grams/day, 30 kg column):
(2→250), (3→330), (4→365), (6→400), (8→410), (10→410), (12→405).
Interpolated monthly kibble (round to whole grams):

Boundary rule: exact 5.0 and 7.0 belong to the later bucket (5.0 → “5–6”, 7.0 → “7–12”).

Use linear interpolation between the nearest kibble reference points listed above.
Round the resulting kibble grams/day to whole grams (or to the nearest 5 g if the user enables a rounding toggle).

Based on the age, assign the corresponding GC bucket and attach that bucket’s low/high range (g/day).

Convert kibble grams/day to kcal/day using the user-provided kibble energy density (kcal/100 g).
Convert kcal/day to GC grams/day using GC’s energy density 115 kcal per 100 g.
(Equivalently, GC provides 1.15 kcal per gram.)
Round to whole grams (or to nearest 5 g if the user toggled it).

Compare the energy-matched GC grams/day to the GC bucket’s low/high:
- “within” if inside [low, high]
- “below” if under the low
- “above” if over the high
  (Do not alter the energy-matched amount; just flag it.)

Default to 7 days (configurable).
Linearly ramp daily fractions from 100% kibble / 0% GC on Day 1 to 0% kibble / 100% GC on the last day, in equal steps.
Each day’s grams = (kibble grams/day × kibble fraction) + (GC grams/day × GC fraction).
Round after multiplying (whole grams or nearest 5 g per the user setting).

Primary number: “Gently cooked (energy-matched): X g/day”.
Directly below, show the GC bucket label and its range (e.g., “7–12 months: 1300–1500 g/day”) plus a small status chip (within/below/above).
Context line: “Based on your kibble energy density: Y kcal / 100 g” with an edit control.
Age input: accept decimals (e.g., 5.5 months).
Add tick marks at 2, 3, 4, 6, 8, 10, 12 (the original kibble points).
Transition widget: a simple 5–7 day table or bar chart that shows kibble g and GC g per day, plus the day total.
(Totals will typically increase during the transition because GC is less energy-dense; this is expected.)
Rounding toggle: whole grams vs nearest 5 g.
Download/export: CSV with columns:
age_months, kibble_g_per_day, kibble_kcal_per_100g, kcal_per_day, gc_energy_matched_g_per_day, gc_bucket_name, gc_low_g, gc_high_g, range_status, and per-day transition grams.

Missing kibble kcal density: block calculation and display a clear prompt to enter kcal/100 g.
Age outside 2–12 months: clamp to the nearest bound; show a subtle informational note.
Energy-matched GC outside bucket range: keep the energy-matched number; display the status chip and a short educational tooltip (growth varies; this tool prioritizes energy continuity).
Rounding: perform all math in floating point; round only for display (and for the per-day plan after multiplying by fractions).

At 5.5 months with 380 kcal/100 g kibble:
- Interpolated kibble ≈ 391 g/day.
- Kcal/day ≈ 1,486 kcal.
- Energy-matched GC ≈ 1,292 g/day.
- GC bucket “5–6 months” (1,250–1,550) → within.
At 8.0 months with 380 kcal/100 g kibble:
- Kibble ≈ 410 g/day → ≈ 1,558 kcal/day → GC ≈ 1,355 g/day.
- GC bucket “7–12 months” (1,300–1,500) → within.
At 2.0 months with 380 kcal/100 g kibble:
- Kibble 250 g/day → 950 kcal/day → GC ≈ 826 g/day.
- GC bucket “<5 months” (950–1,350) → below (expected for some formulas).