Pet Food Calculator

Resting Energy Requirement (RER)

The calculator starts from the widely used allometric formula for a pet's resting energy needs:

RER = 70 × (body weight in kg)^0.75

This gives the number of calories (kcal) an animal needs each day at complete rest.

Maintenance Energy Requirement (MER)

The RER is then multiplied by life-stage, activity, and body-condition factors to get the daily Maintenance Energy Requirement — the real-world calories needed:

MER = RER × life-stage × activity × condition

• Life stage: growing animals need more energy than adults; seniors typically need less.
• Activity: working or highly active pets burn more; sedentary indoor pets burn less.
• Body condition: overweight pets are fed toward a target weight; neutered pets need slightly fewer calories.

Grams of Food

Finally, the daily calories are divided by the food's calorie density to get a portion in grams:

Grams per day = MER ÷ (kcal per 100 g) × 100

Split this total across the number of meals you feed per day.

Typical Calorie Densities

• Dry kibble (dog / cat): ~300–450 kcal / 100 g
• Wet / canned food: ~70–120 kcal / 100 g
• Rabbit pellets: ~200–300 kcal / 100 g (plus unlimited hay)