Resting Energy Requirement — The Starting Point
RER is the calorie floor a cat burns at rest.
- 70·W^0.75: Formula (kcal/day, W in kg)
- ~200-280: Typical adult (kcal/day at 4kg)
- Metabolic mass: Basis (allometric scaling)
- Baseline only: Use (before multipliers)
Why RER matters
RER anchors every later multiplier in this calculator.
Life-Stage Multiplier — Kitten, Adult, Senior
Growth and aging shift energy needs up or down.
- 2.0-3.0x: Kitten (rapid growth phase)
- 1.2-1.6x: Adult (maintenance range)
- 1.0-1.4x: Senior (lower activity, mass)
- up to 3.0x: Pregnant/lactating (reproductive demand)
Choosing a multiplier
Pick the range matching the cat's current life stage.
Indoor vs Outdoor Activity Multiplier
Outdoor and active cats burn noticeably more calories.
- 1.0-1.2x: Indoor, inactive (low movement)
- 1.2-1.4x: Indoor, average (typical apartment cat)
- 1.4-1.8x: Outdoor access (roaming, hunting)
- up to 2.5x: Working/athletic (very high activity)
Activity adjustment
More movement raises the multiplier used in MER.
Neuter Status Adjustment
Neutered cats generally need slightly fewer calories.
- +10-20%: Intact (higher baseline need)
- -10%: Neutered/spayed (lower metabolic rate)
- 1.2 vs 1.4: Common factor (neutered vs intact adult)
- Obesity risk: Why it matters (post-surgery weight gain)
Adjusting for surgery status
Lower the multiplier slightly after spay or neuter.
Final Daily MER and Food Portion
All factors combine into calories and grams of food.
- RER × mult: Formula (= MER kcal/day)
- ~3.5 kcal/g: Dry food (typical energy density)
- MER ÷ 3.5: Portion (grams per day)
- 2-3 meals: Split (recommended feeding)
Reading the result
Use the portion estimate as a starting feeding guide.
Always confirm portions with a veterinarian for the individual cat.