How do I calculate a weight loss plan for both my cat and my dog without visiting a vet or buying a smart scale?

Paws & Pounds is 100% software-based. Use your regular home scale, complete our visual 9-point BCS assessment, and our algorithm calculates the exact RER/DER daily calories and portion size in grams. No smart scale, no vet visit required for initial assessment.

Is the Paws & Pounds app free to use?

Yes! The free tier lets you manage 1 pet, track unlimited weight entries, use the visual BCS tool, and get a daily feeding plan. Paws & Pounds Pro ($4.99/month or $29.99/year) unlocks unlimited pets, household collaboration, advanced analytics, and CSV export.

Can my partner also log feeding times?

Absolutely. Paws & Pounds Pro includes Household Collaboration — invite family members by email, and everyone in the household can log feedings, record weights, and see real-time status so nobody accidentally double-feeds your pet.

What is a Body Condition Score (BCS) and why is it better than weight alone?

Body Condition Score is a veterinary-standard 9-point scale that evaluates your pet's fat coverage through visual and hands-on checks. Unlike weight alone, BCS accounts for breed, frame size, and muscle mass. A 12-pound Maine Coon may be underweight while a 12-pound Siamese could be obese — BCS captures this difference.

How does Paws & Pounds compare to PetDesk, Pet Weight Tracker, or spreadsheet tracking?

Unlike general-purpose apps or spreadsheets, Paws & Pounds combines visual BCS assessment, veterinary-grade RER/DER calorie math, and a daily feeding plan in grams — all in one app. It covers 270+ breeds across cats and dogs, supports household collaboration, and gives you actionable portion sizes instead of just weight charts.

Which breeds does Paws & Pounds support?

Paws & Pounds includes a database of over 270 dog and cat breeds with breed-specific ideal weight ranges. If your pet is a mixed breed, you can enter a custom target weight based on your vet's recommendation.

How accurate is the calorie calculation?

Paws & Pounds uses the same RER (Resting Energy Requirement) and DER (Daily Energy Requirement) formulas used by veterinary nutritionists worldwide: RER = 70 × (body weight in kg)^0.75. We then apply species-specific, age, and neutered/intact multipliers to compute the daily calorie target.

Can I use Paws & Pounds for a puppy or kitten?

Yes. The app includes life-stage multipliers for kittens and puppies, which have higher energy requirements than adults. Select the appropriate life stage during pet setup and the feeding plan adjusts automatically.

Is my pet's data secure?

All data is stored in a secure, encrypted Supabase database with row-level security. Data is bound to your household — only invited household members can access it. We never sell or share your data with third parties.

What if my pet has a medical condition affecting their weight?

Paws & Pounds provides general nutritional guidance based on established veterinary formulas. If your pet has diabetes, thyroid issues, kidney disease, or other medical conditions, always consult your veterinarian before making dietary changes. The app's feeding plan is a starting point, not a replacement for professional veterinary advice.

How many calories does my cat need per day?

Most spayed or neutered indoor adult cats need roughly 20 kcal per pound of ideal body weight per day (about 45 kcal per kg). A 10 lb (4.5 kg) cat therefore needs ≈ 200 kcal/day at maintenance. The calculator refines this using the veterinary RER formula (70 × kg^0.75) plus activity and neuter multipliers.

What is the resting energy expenditure (REE) of a cat?

In practice, REE (resting energy expenditure) is used similarly to RER (Resting Energy Requirement): the calories needed to maintain basic body functions at rest. For cats, the standard veterinary estimate is RER = 70 × (kg)^0.75. This calculator uses that RER/REE baseline and then applies an activity and neuter multiplier to estimate the daily feeding target (MER/DER).

Is RER the same as REE for cats?

They are used very similarly in everyday feeding guidance. REE is a measured metabolic rate (often via indirect calorimetry), while RER is a practical veterinary estimate used for diet planning. For most pet owners, treating REE as the RER baseline is reasonable: start with RER = 70 × (kg)^0.75, then adjust up or down using a multiplier based on life stage, neuter status, and weight goal.

What is MER vs DER (and how is it different from RER)?

RER is the resting baseline (calories burned at rest). MER (Maintenance Energy Requirement) and DER (Daily Energy Requirement) are practical daily feeding targets after applying a multiplier to RER based on factors like neuter status, activity, and weight-loss vs maintenance. Different sources use MER/DER terms differently, but the workflow is the same: calculate RER first, then apply the right multiplier for the goal.

What formula does this calculator use?

Resting Energy Requirement (RER) = 70 × body-weight-in-kg^0.75. The Daily Energy Requirement (DER) multiplies RER by a factor of 1.0 for weight loss, 1.2 for a neutered indoor cat at maintenance, or 1.4 for an intact, highly active cat. These multipliers come from the WSAVA Global Nutrition Toolkit and the AAHA Weight Management Guidelines.

How much should I feed my cat to lose weight?

Feed roughly 0.8 × RER kcal per day. Expect no more than ~1–2% of body weight lost per week. For a 12 lb (5.4 kg) cat, weight-loss RER ≈ 183 kcal/day. Weigh the food on a kitchen scale, split across 2–3 meals, and recheck weight every 2 weeks.

Is this calculator accurate for kittens or pregnant cats?

No. Kittens, pregnant queens, and lactating cats have much higher energy needs (up to 3× RER) and require life-stage–specific plans. Consult your veterinarian for those life stages.

Why does my cat need fewer calories after being neutered?

Neutering lowers a cat's basal metabolic rate and increases appetite, reducing maintenance energy needs by roughly 20–25%. Adjusting calories after the procedure is the single most effective way to prevent post-neuter weight gain.

What's the difference between RER and DER?

RER (Resting Energy Requirement) is the calories a cat burns at rest, just to stay alive. DER (Daily Energy Requirement) is RER multiplied by an activity/life-stage factor — it's the actual daily calorie target for feeding.

Do I need a smart scale or vet visit to use this?

No. Weigh yourself on a regular home scale, then weigh yourself holding your cat, and subtract. Combined with a visual Body Condition Score assessment, this is enough to produce a reliable feeding plan at home.

Cat RER Calculator: Daily Calories & MER by Weight

Free cat RER / MER calorie calculator — daily kCal by weight, grams, treat allowance. No sign-up.

Science-based feeding calculator using the WSAVA/AAHA Resting Energy Requirement formula. All math runs in your browser.

By Paws & Pounds Research Team — reviewed against WSAVA/AAHA guidelines. Last updated September 18, 2026.

Your cat's details

Results update instantly.

Units

Current weight (lb)

Target (ideal) weight (lb)

Use vet's target or breed midpoint. Match current weight for maintenance.

Spayed / neutered

Neutered cats typically need ~20% fewer calories.

Activity level

Food energy density (optional)

kcal / 100 g

Optional. Enter to calculate daily portion in grams.

Daily feeding plan

Daily target

200kcal / day

Safe weight-loss calorie target.

Main meals (90%): 180 kcal
Treats max (10%): 20 kcal
RER: 249 kcal
DER (maintenance): 299 kcal
Safe pace: Target max 0.11 kg change per week (~2% of body weight). Estimated 9 weeks to reach the goal.

Estimate only. Individual metabolism varies. Consult your veterinarian before changing your cat's diet — especially for kittens, pregnant queens, or cats with diabetes, kidney disease, or thyroid issues.

Save this calorie plan & share with your household

The app keeps your cat's kcal target, logs meals so nobody double-feeds, and charts weight for your vet.

Download on the App Store Convert cups → grams

View calculation formulas & math

Calculations follow the veterinary standards outlined in the WSAVA Global Nutrition Guidelines and the AAHA Weight Management Guidelines.

1. Resting Energy Requirement (RER)

RER (kcal/day) = 70 × (Body Weight in kg)^0.75

For your cat's target weight (4.54 kg): 249 kcal/day.

2. Daily Energy Requirement (DER)

Weight Loss factor: RER × 0.8

This results in the target budget of 200 kcal/day.

3. Portion Division (90/10 Rule)

Main Meals (90%): 180 kcal
Treat Allowance (10% max): 20 kcal

Quick answer

A healthy adult spayed/neutered indoor cat needs about 20 kcal per pound(45 kcal/kg) of ideal body weight per day. For weight loss, reduce this to about 0.8 × RER (70 × kg^0.75). Split the daily portion across 2–3 meals and aim for no more than 1–2% body-weight loss per week.

How the calculation works

The calculator follows the two-step formula used by veterinary nutritionists worldwide:

RER (Resting Energy Requirement) = 70 × body-weight-in-kg^0.75. This is the calories your cat would burn simply lying still all day.
DER (Daily Energy Requirement) = RER × activity factor. Typical factors:
- 1.0 — weight loss
- 1.2 — neutered indoor adult (default)
- 1.4 — intact, very active
- 1.2 × 1.2 — supervised gradual weight gain

The daily calorie target is then split 90% main food / 10% treats. If you enter the food's kcal per 100 g, the calculator converts the main-food kcal into grams so you can weigh it directly on a kitchen scale.

Weight-loss pace: we cap the recommended weekly loss at 2% of body weight — any faster and cats risk hepatic lipidosis, a potentially fatal liver condition.

RER to MER/DER multiplier table (cats)

Reference for “cat calorie calculator by weight” and “RER MER cat” searches. Values match the calculator above.

Feline RER to MER/DER multipliers per WSAVA and AAHA weight management guidelines
Goal / life stage	Multiplier	Notes
Step 1 — RER (Resting Energy Requirement) = 70 × weight_kg^0.75 kcal/day
Weight loss	RER × 0.8	Max 1–2% body weight lost per week
Neutered indoor adult (maintenance)	RER × 1.2	Default for most indoor pet cats
Intact, very active	RER × 1.4	Outdoor or high-activity cats
Supervised weight gain	RER × 1.2	Applied to maintenance DER (×1.2)
Treat allowance: ≤10% of daily kcal budget; main food gets the remaining 90%.

Frequently asked questions

How many calories does my cat need per day?: Most spayed or neutered indoor adult cats need roughly 20 kcal per pound of ideal body weight per day (about 45 kcal per kg). A 10 lb (4.5 kg) cat therefore needs ≈ 200 kcal/day at maintenance. The calculator refines this using the veterinary RER formula (70 × kg^0.75) plus activity and neuter multipliers.
What is the resting energy expenditure (REE) of a cat?: In practice, REE (resting energy expenditure) is used similarly to RER (Resting Energy Requirement): the calories needed to maintain basic body functions at rest. For cats, the standard veterinary estimate is RER = 70 × (kg)^0.75. This calculator uses that RER/REE baseline and then applies an activity and neuter multiplier to estimate the daily feeding target (MER/DER).
Is RER the same as REE for cats?: They are used very similarly in everyday feeding guidance. REE is a measured metabolic rate (often via indirect calorimetry), while RER is a practical veterinary estimate used for diet planning. For most pet owners, treating REE as the RER baseline is reasonable: start with RER = 70 × (kg)^0.75, then adjust up or down using a multiplier based on life stage, neuter status, and weight goal.
What is MER vs DER (and how is it different from RER)?: RER is the resting baseline (calories burned at rest). MER (Maintenance Energy Requirement) and DER (Daily Energy Requirement) are practical daily feeding targets after applying a multiplier to RER based on factors like neuter status, activity, and weight-loss vs maintenance. Different sources use MER/DER terms differently, but the workflow is the same: calculate RER first, then apply the right multiplier for the goal.
What formula does this calculator use?: Resting Energy Requirement (RER) = 70 × body-weight-in-kg^0.75. The Daily Energy Requirement (DER) multiplies RER by a factor of 1.0 for weight loss, 1.2 for a neutered indoor cat at maintenance, or 1.4 for an intact, highly active cat. These multipliers come from the WSAVA Global Nutrition Toolkit and the AAHA Weight Management Guidelines.
How much should I feed my cat to lose weight?: Feed roughly 0.8 × RER kcal per day. Expect no more than ~1–2% of body weight lost per week. For a 12 lb (5.4 kg) cat, weight-loss RER ≈ 183 kcal/day. Weigh the food on a kitchen scale, split across 2–3 meals, and recheck weight every 2 weeks.
Is this calculator accurate for kittens or pregnant cats?: No. Kittens, pregnant queens, and lactating cats have much higher energy needs (up to 3× RER) and require life-stage–specific plans. Consult your veterinarian for those life stages.
Why does my cat need fewer calories after being neutered?: Neutering lowers a cat's basal metabolic rate and increases appetite, reducing maintenance energy needs by roughly 20–25%. Adjusting calories after the procedure is the single most effective way to prevent post-neuter weight gain.
What's the difference between RER and DER?: RER (Resting Energy Requirement) is the calories a cat burns at rest, just to stay alive. DER (Daily Energy Requirement) is RER multiplied by an activity/life-stage factor — it's the actual daily calorie target for feeding.
Do I need a smart scale or vet visit to use this?: No. Weigh yourself on a regular home scale, then weigh yourself holding your cat, and subtract. Combined with a visual Body Condition Score assessment, this is enough to produce a reliable feeding plan at home.

Cat calorie charts by breed & weight

Prefer a ready-made table for a common breed weight? Open a pilot chart (lb steps) with RER/MER and grams estimates.

Save this calorie plan & share with your household

The Paws & Pounds app saves your cat's kcal target, logs meals so nobody double-feeds, and charts weight trends to share with your vet.

Download on the App Store Read the weight-management guide

Sources & further reading

WSAVA Global Nutrition Toolkit — Calorie Calculation & Body Condition Assessment — World Small Animal Veterinary Association, 2021
2014 AAHA Weight Management Guidelines for Dogs and Cats — American Animal Hospital Association, 2014
Nutrient Requirements of Dogs and Cats — National Research Council (NRC), 2006
AAFP Feline Life Stage Guidelines — Nutrition and feeding recommendations — American Association of Feline Practitioners, 2021