pet-food-calculator

Pet Food Calculator 🐾

Compute exactly how much to feed your dog or cat — daily calories, grams per meal, feeding schedule, cost per month, and weight-loss trajectory — from species, weight, age, activity, and body-condition score. Flags weight-loss plans with safe calorie floors (never starve a cat) and builds transition schedules for switching foods.

Overview

Pet obesity affects over half of dogs and cats, shaving ~2 years off life expectancy, and the #1 cause is simple overfeeding — owners guess portions, food bags' guidelines are deliberately generous, and cups are imprecise. Vet nutrition formulas (RER → MER) are well-established but require a calculator nobody owns.

pet_food_calculator.py implements the veterinary-standard math:

• RER (Resting Energy Requirement) = 70 × (ideal weight kg)^0.75
• MER (Maintenance) = RER × factor from species/age/activity/reproductive status
• Weight loss: targeted at RER × 0.8-1.0 for dogs, never below ~0.5×RER / strict floors for cats (hepatic lipidosis risk)
• Portions in grams/day from any food's kcal/kg (printed on every bag)
• Cost comparison across foods (dry/wet/premium/vet prescription)
• Food transition schedule (25/50/75% over 7 days)
• Multi-pet household plan with per-animal feeding windows

When to Use

• "How much should I feed my dog/cat?" — daily portions in grams and calories
• "Is my pet overweight?" — body-condition scoring guide + target weight
• "My vet said to put him on a diet" — safe weight-loss plan with timeline
• Comparing food costs before switching brands
• "How do I switch foods without stomach upset?" — transition schedule
• Puppy/kitten growth feeding (their energy factors are wildly different)
• Senior pets, pregnant/nursing animals, working/sporting dogs

Don't use for: diagnosing illness, prescription diets for renal/urinary conditions (follow vet guidance), or exotic pets (formulas are dog/cat only).

Quick Start

# Adult neutered dog, 30 kg, moderate activity, food is 3800 kcal/kg
python3 scripts/pet_food_calculator.py --species dog --weight 30 \
  --age adult --activity moderate --food-calories 3800

# Overweight cat: 7.2 kg current, target 5.5 kg
python3 scripts/pet_food_calculator.py --species cat --weight 7.2 \
  --target-weight 5.5 --food-calories 4800

# Puppy, 5 kg, expecting ~25 kg adult
python3 scripts/pet_food_calculator.py --species dog --weight 5 \
  --age puppy --adult-weight 25 --food-calories 4100

# Compare monthly cost of two foods
python3 scripts/pet_food_calculator.py --species dog --weight 30 \
  --age senior --food-calories 3400 --food-price 65 --bag-kg 12

# Full household plan (JSON out)
python3 scripts/pet_food_calculator.py --species cat --weight 4.5 \
  --age adult --food-calories 5000 --json plan.json

The Math (what the vet does)

1. RER = 70 × W^0.75 (W = ideal/target weight, not current!)
2. Factor — dog adult neutered 1.6, intact 1.8, senior 1.4, puppy 4-month ~2.7→1.6 by 12mo, weight loss 1.0; cat adult neutered 1.2, intact 1.4, senior 1.1, weight loss 0.8×RER (floor!)
3. MER = RER × factor → kcal/day
4. Grams/day = MER ÷ (food kcal/kg ÷ 1000)
5. Treats ≤ 10% of daily calories — the report reserves that budget

Common Pitfalls

1. Using current weight for overweight pets. Energy needs are computed at ideal/target weight — feeding a 40 kg obese dog like a 40 kg dog perpetuates the obesity. Use --target-weight.
2. Crash-dieting cats. Cats fasting or severely underfed develop hepatic lipidosis, which is life-threatening. The calculator enforces feline floors (~0.5×RER and ≥18 kcal per kg ideal weight) and warns.
3. Trusting bag guidelines. They're set for the most active animals and rounded up; calculating from kcal/kg is exact.
4. Ignoring treats. A dental chew can be 10% of a small dog's daily calories. Keep the 10% budget.
5. Switching foods cold-turkey. GI upset follows; the generated 7-day transition (25→50→75→100%) prevents it.
6. Volume ≠ weight. A "cup" of dense kibble can vary 20% in calories; grams on a kitchen scale are the only honest unit.

Verification Checklist

• Species/age/activity factors match the animal's real state
• Target weight (not current) used for overweight pets
• Food kcal/kg read from the bag's "metabolizable energy" line (kcal/kg, not kcal/cup)
• Weight-loss rate for dogs ≤ 1-2% body weight per week
• Cat plans respect the calorie floor and show no fasting
• Transition schedule printed when switching foods (--transition)

References

• references/energy-requirements.md — full factor tables, growth curves, BCS guide
• references/feeding-guide.md — meal frequency by age, transition schedules, treat budget, food-label decoding