Cat Calorie Calculator
How many calories does my cat need? Enter a body weight and this cat calorie needs calculator gives the resting energy requirement (RER) and the daily maintenance energy requirement (MER) used in veterinary nutrition — then converts the target into grams of food per day. Free, unlimited, and no account required.
Calculate daily calories
Resting energy (RER)
216 kcal / day
Daily energy (MER)
260 kcal / day
This is an estimate for healthy cats. Growing kittens, pregnant or lactating queens, and patients on therapeutic diets need a veterinary feeding plan.
Turn calories into a portion
Calories are only the middle step — what you actually feed is grams. Take the energy figures from the bag or tin label and get the daily portion.
Usually printed as “metabolisable energy” on the label.
Only some labels give this. Grams are always more accurate than cups.
Daily portion
65 g / day
Your label says 4000 kcal per kg, so feed about 65 g per day to reach 260 kcal.
In cups
Add the kcal per cup from the label to see a cup measure. Cups vary a lot between foods, so weigh the food when you can.
This calculator stays free
The cat calorie calculator, the RER chart and the calories-to-grams conversion on this page are free to use as often as you like, with no account. An account adds the verified product catalog with real energy densities, printable client handouts, prescription diet support, food transitions and parasite dosing for your clinic.
How the cat calorie calculation works
Every veterinary calorie calculator starts with the resting energy requirement, the energy a cat uses at rest before activity, growth, reproduction or temperature stress. It is calculated with the allometric equation:
A 4.5 kg cat therefore has a RER of about 217 kcal per day. RER alone is not a feeding recommendation; it is multiplied by a life-stage factor to give the maintenance energy requirement:
Life-stage factors for cats
| Patient | Factor |
|---|---|
| Neutered adult cat | RER × 1.2 |
| Intact adult cat | RER × 1.4 |
| Indoor, low activity cat | RER × 1.0 |
| Weight loss cat | RER × 0.8 |
| Weight gain cat | RER × 1.6 |
| Kitten, growing cat | RER × 2.5 |
Cat factors are noticeably lower than dog factors. Neutering reduces energy needs while appetite often stays the same, which is why indoor neutered cats gain weight so easily on a portion that looks small.
RER chart for cats by body weight
Resting energy requirement at a glance, with the two most common adult maintenance factors. Use it as a sanity check on the calculator above.
| Weight | RER (kcal/day) | Neutered adult (×1.2) | Intact adult (×1.4) |
|---|---|---|---|
| 2 kg (4.4 lb) | 118 | 142 | 165 |
| 2.5 kg (5.5 lb) | 139 | 167 | 195 |
| 3 kg (6.6 lb) | 160 | 192 | 224 |
| 3.5 kg (7.7 lb) | 179 | 215 | 251 |
| 4 kg (8.8 lb) | 198 | 238 | 277 |
| 4.5 kg (9.9 lb) | 216 | 259 | 302 |
| 5 kg (11 lb) | 234 | 281 | 328 |
| 5.5 kg (12.1 lb) | 251 | 301 | 351 |
| 6 kg (13.2 lb) | 268 | 322 | 375 |
| 7 kg (15.4 lb) | 301 | 361 | 421 |
| 8 kg (17.6 lb) | 333 | 400 | 466 |
Chart values are rounded. Growing, pregnant, lactating, underweight or hospitalised patients use different factors and need a veterinary feeding plan.
From calories to grams of food
Once you have the daily calorie target, divide it by the food’s energy density to get the daily ration:
Most dry cat foods sit between 3.5 and 4.3 kcal per gram, and wet food is far more dilute, so the same calorie target can mean very different bowl sizes. Vet.Portions holds the calorie content of thousands of regional products so your team never has to look it up on the bag.
Built for veterinary clinics
The full Vet.Portions dashboard turns this calculation into a printable client handout, with product-specific gram amounts, meal splits, food transition schedules and parasite dosing support.
Frequently asked questions
- How many calories does a cat need per day?
- Calculate RER = 70 × (weight in kg)0.75, then multiply by the factor that matches the cat. A 4.5 kg neutered adult cat needs roughly 260 kcal per day.
- Why are cat calorie factors lower than dog factors?
- Adult cats sit around 1.0 to 1.4 times RER, while adult dogs commonly use 1.6 to 1.8. Cats are less active across a day and gain weight readily after neutering.
- Is a veterinary calorie calculator accurate for every cat?
- No. It is a clinical support tool. Recheck body weight and body condition every two to four weeks and adjust the amount with your veterinarian.