Cat Weight Loss Calculator

Help your cat slim down safely with this free cat weight loss calculator. It works out a safe daily calorie target and deficit from your cat’s ideal weight, shows the timeline to goal, checks your loss rate is safe, converts calories into food portions, and tracks progress week by week.

Cats must lose weight slowly — about 0.5–2% of body weight a week. Losing weight too fast, or starving a cat, can cause hepatic lipidosis (fatty liver disease), which can be fatal. This is a starting guide; plan any diet with your veterinarian, especially for a cat that has lost its appetite.

Enter current and target (ideal) weight for a safe daily calorie target — vets feed to the goal weight, not the current one.






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to feed per day

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In food
Per day
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Calorie cut
Vs maintenance
10%
Treat limit
Max of kcal

How long will it take? Enter the weights and a safe weekly loss rate.




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to reach target

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In months
Approx.
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Per week
To lose
~1 lb
Per month
Rough max

Is your cat losing weight at a safe pace? Enter the weight lost over a week or a month.




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loss-rate check

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Of body weight
Per week
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Safe ceiling
2%/week
0.5–2%
Safe band
Per week

Turn the daily calorie target into measured portions. Enter the kcal from your food’s label.




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dry food per day

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Or wet food
Per day
—
Treat budget
10% of kcal
2+ meals
Split it
Measured

Track progress and spot a plateau. Enter starting weight, current weight and weeks on the diet.




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progress check

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Lost so far
Total
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Average rate
Per week
—
Of body weight
Per week


How the Cat Weight Loss Calculator Works

This cat weight loss calculator builds a safe diet plan around the single most important rule vets and the r/dechonkers community agree on: feed for your cat’s ideal weight, not its current weight. It finds the daily calorie target from the Resting Energy Requirement (RER = 70 × ideal kg0.75) at the goal weight, then feeds about 80% of it for a safe calorie deficit — a quick cross-check is 20–25 calories per pound of ideal weight. For a cat whose ideal weight is 4.5 kg (10 lb), that is roughly 180–200 calories a day. The calculator also turns calories into cup, can and gram portions, projects the timeline to goal, and checks the loss rate stays in the safe 0.5–2% of body weight per week. Staying in that band matters: losing weight too fast can trigger hepatic lipidosis, a dangerous fatty-liver condition, so slow and steady is the whole game.

The five tools cover weight-loss calories, the timeline to goal, a safe-rate check, food portions, and a weekly tracker.

How to Calculate Cat Weight Loss Calories

The vet method is a two-step calculation based on the target weight. First, find the Resting Energy Requirement at the goal weight: RER = 70 × (ideal weight in kg)0.75 (a simpler version is 30 × kg + 70). Then feed roughly 80% of that RER for weight loss. The reason you use the ideal weight is safety — basing calories on a heavy current weight would feed the cat too much and stall the diet, while crash-cutting from current maintenance can be dangerous. Most overweight indoor cats land somewhere around 120–220 calories a day on a weight-loss plan, well below the 200–250 they burn at their current size. Always divide treats into that total — they should be no more than 10% of daily calories.

How Much Weight Can a Cat Lose in a Month?

A safe rate is about 0.5% to 2% of body weight per week, which works out to roughly 2–5% of body weight per month — in practical terms, often about half a pound to one pound (0.2–0.5 kg) a month for a typical cat. For a 15 lb cat that is only around 0.1–0.3 lb a week. It feels slow, and that is the point: a cat that loses weight too quickly, or stops eating, is at real risk of hepatic lipidosis (fatty liver disease), where the liver is overwhelmed by mobilised fat. The Timeline tab shows how many weeks your goal will realistically take, and the Safe Rate tab flags a pace that is too fast.

Is 200 Calories a Day Enough for a Cat?

For many cats, yes — around 200 calories a day is a normal maintenance amount for an average 10 lb (4.5 kg) neutered indoor cat. For weight loss, the target is usually a bit lower, often 150–190 calories depending on the ideal weight, because you feed to the goal size and apply the deficit. Whether 200 is right depends entirely on your cat’s ideal weight and activity: a small cat aiming for 8 lb needs fewer, a larger-framed cat more. Rather than guess, enter the numbers above — and if your cat is eating far less than calculated and still not losing (or is losing fast), check in with your vet.

A Safe Cat Weight-Loss Plan (Step by Step)

Start by confirming the ideal weight with a body condition score, then set the daily calories from that goal weight (the Loss Calories tab). Measure every meal in grams on a kitchen scale rather than scooping, and read the kcal per cup or can off the bag, since brands vary widely. Many owners find a higher-protein or canned diet keeps a cat fuller on fewer calories, with an adjustment period of extra vocal begging. Weigh the cat weekly on the same scale and log it; if the weight stalls for three to four weeks, trim calories another 5–10%. Reassess body condition every few weeks, keep treats within the 10% budget, and add short play sessions for activity. Above all, keep the pace gentle and loop in your vet for a cat with any health condition.

Frequently Asked Questions

How do I calculate my cat’s weight loss calories?
Use the target (ideal) weight: calculate RER = 70 x (ideal kg)^0.75, then feed about 80% of it. A quick cross-check is 20 to 25 calories per pound of ideal weight. The Loss Calories tab does this and converts it into food portions.
How much weight can a cat lose in a month?
Safely about 2 to 5% of body weight a month (0.5 to 2% a week), which is often around half a pound to a pound. Faster than that risks hepatic lipidosis, a dangerous fatty-liver condition, so aim for slow, steady loss.
Is 200 calories a day enough for a cat?
About 200 calories a day is typical maintenance for an average 10 lb indoor cat. For weight loss the target is usually a little lower, often 150 to 190 calories, based on the ideal weight. Enter your cat’s numbers above for an exact figure.
How many calories help a cat lose weight?
Feed roughly 80% of the RER at the target weight. For most overweight cats that falls around 120 to 200 calories a day, below the 200 to 250 they burn at their current size. Keep treats to 10% of the total.
Why should I feed for ideal weight instead of current weight?
Basing calories on a heavy current weight feeds too much and stalls the diet, while crash-cutting is risky. Feeding to the ideal weight sets a gentle, effective deficit. This is the consensus among vets and weight-loss communities like r/dechonkers.
What is the fastest safe way for a cat to lose weight?
There is no safe fast way. Stay at or below 2% of body weight a week, feed a measured, protein-rich or vet weight-loss diet, cut treats, and add activity. Never withhold food or crash-diet, which can cause fatal fatty-liver disease.
My cat stopped losing weight — what do I do?
Plateaus are normal. If the weight has not moved for three to four weeks and you are measuring food accurately, trim daily calories by 5 to 10% and recheck. Make sure no one else is feeding the cat and that treats are counted. The Tracker tab flags this.

More Cat & Pet Calculators

🐱Cat Calorie CalculatorDaily kcal needs
🍽Cat Food CalculatorHow much to feed
⚖Cat BMI CalculatorFeline BMI & weight
🐱Body Condition ScoreScore 1–9
❤Cat Life ExpectancyHow long cats live
🐈Cat Age CalculatorCat years to human

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PetCalculatorHub Editorial Team
Weight-loss calories here use the veterinary RER formula (70 × kg^0.75) applied to the target weight at about 80%, with safe-loss limits of 0.5–2% of body weight per week. These are starting estimates to help you plan at home, not a prescription. Food calorie density varies by brand, so read your label and weigh portions in grams. Always design a weight-loss plan with your veterinarian — and seek care promptly for any cat that loses weight rapidly or stops eating, which can signal life-threatening hepatic lipidosis.
For weight-loss and calorie guidance, see the OSU Veterinary Medical Center and the AAHA Weight Management Guidelines.
Last updated: October 2026