# Dog weight: is my dog overweight?

Estimates a dog’s ideal weight from its current weight and body condition score (9-point scale), how much it is over, and how many weeks a safe weekly weight loss takes, with the weight drawn week by week.

- Page: https://www.acalculator.org/biology/dog-weight-calculator
- JSON spec: https://www.acalculator.org/biology/dog-weight-calculator.json
- Version: 246606f6553f

## Default answer

Example with the default inputs (Current weight 60 lb, Body condition score 7: overweight, Weight loss per week 1%): Ideal weight: about 50 lb (22.7 kg) for a 60 lb dog (Overweight).

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| w | Current weight | Your dog’s weight today. |
| bcs | Body condition score | Your dog’s body condition score on the 9-point scale, from 1 (very thin) to 9 (very obese); 4 and 5 are ideal. |
| rate | Weight loss per week | The share of body weight to lose each week, from 0.5% to 2%; the AAHA guidelines give 1% to 2% for dogs. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| ideal | Ideal weight (lb) | The estimated ideal weight in pounds: current weight ÷ (1 + 0.1 × (score − 5)), or the current weight at a score of 4 or 5. |
| idealKg | Ideal weight (kg) | The estimated ideal weight in kilograms. |
| category | Body condition | Ideal, above ideal, overweight or obese, from the score. |
| over | Over ideal weight | How much heavier than ideal the dog is, as a percent of the ideal weight: 10% per score point above 5. |
| lose | Weight to lose | Current weight − ideal weight, in pounds. |
| loseKg | Weight to lose (kg) | Current weight − ideal weight, in kilograms. |
| weeks | Weeks to ideal weight | Whole weeks until the weekly weight, losing the chosen percent of body weight each week, is at or below the ideal weight. |

## Method

ideal weight = current weight ÷ (1 + 0.1 × (BCS − 5)) = 10 × weight ÷ (BCS + 5) for a score of 5 to 9 (4 is ideal); weeks = the first whole n with weight × (1 − rate)ⁿ ≤ ideal weight.

## Assumptions

- Uses the 9-point body condition score: 4 and 5 are ideal, and each point above 5 is about 10% over ideal weight (6 is 10%, 7 is 20%, 8 is 30%, 9 is 40%), as in the AAHA 2014 weight management guidelines. It is an estimate: your vet can check the score and the target.
- Scores of 1 to 3 (underweight) give no answer here.
- Each week the dog loses the chosen percent of its weight at the start of that week; the AAHA guidelines give 1% to 2% a week for dogs. The weeks count to the first weekly weigh-in at or below the ideal weight.
- Weights are from 0.2 to 150 kg (0.44 to 331 lb). The chart shows kilograms.

## Worked examples

1. w = 27.215542, bcs = 7, rate = 1% gives ideal = 50, idealKg = 22.679619, over = 20%, lose = 10, loseKg = 4.535924, weeks = 19, category = Overweight. Source: Brooks et al. (2014), AAHA Weight Management Guidelines for Dogs and Cats, J Am Anim Hosp Assoc 50(1):1–11 (BCS 7/9 is about 20% over ideal; lose 1–2% of body weight a week), https://www.researchgate.net/publication/258444230_2014_AAHA_Weight_Management_Guidelines_for_Dogs_and_Cats.
2. w = 30, bcs = 9, rate = 2% gives ideal = 47.241913, idealKg = 21.428571, over = 40%, lose = 18.896765, loseKg = 8.571429, weeks = 17, category = Obese. Source: Brooks et al. (2014), AAHA Weight Management Guidelines (BCS 9/9 is about 40% over ideal).
3. w = 9.979032, bcs = 6, rate = 1.5% gives ideal = 20, idealKg = 9.071847, over = 10%, lose = 2, loseKg = 0.907185, weeks = 7, category = Above ideal.
4. w = 25, bcs = 5, rate = 1% gives idealKg = 25, over = 0%, lose = 0, loseKg = 0, weeks = 0, category = Ideal.

## FAQ

### How do I know if my dog is overweight?

Use the body condition score, which vets rate from 1 to 9 by look and feel. At the ideal 4 or 5 you can feel the ribs under a thin layer of fat and see a waist from above. At 6 there is a little extra fat; at 7 the ribs are hard to feel; at 8 or 9 there is no waist and there are fat deposits on the back and tail base.

### How do I work out my dog’s ideal weight?

Each body condition score point above 5 is about 10% over ideal weight, so divide the current weight by 1 + 0.1 × (score − 5). A 60 lb dog with a score of 7 is about 20% over: 60 ÷ 1.2 = 50 lb ideal.

### How fast should a dog lose weight?

The American Animal Hospital Association (AAHA) guidelines give 1% to 2% of body weight a week for dogs. At 1% a week, the 60 lb dog above takes about 19 weeks to reach 50 lb. Faster loss can harm health, so plan the diet with your vet.

### Why does the chart curve instead of falling in a straight line?

Each week the dog loses a percentage of its weight at that time, so the pounds lost each week get a little smaller as the dog gets lighter. A 60 lb dog at 1% loses 0.6 lb in the first week and about 0.5 lb a week near 50 lb.

### What if my dog is underweight?

A score of 1 to 3 means too thin. This calculator estimates ideal weight for dogs at or above ideal, so it gives no answer for those scores. A thin dog may have a health problem, so see your vet.

### How accurate is the ideal weight?

It is an estimate. The 10% per point rule is an average, and scoring by eye varies between people. Your vet can confirm the score and set a target weight, and weighing every week or two shows whether the plan works.

## Sources

- Brooks, D., J. Churchill, K. Fein, D. Linder, K. E. Michel, K. Tudor, E. Ward, and A. Witzel (2014). 2014 AAHA Weight Management Guidelines for Dogs and Cats. Journal of the American Animal Hospital Association 50(1), 1–11 (9-point BCS: 6/9 about 10% over ideal, 7/9 about 20%; weight loss of 1–2% a week for dogs). https://www.researchgate.net/publication/258444230_2014_AAHA_Weight_Management_Guidelines_for_Dogs_and_Cats
- Laflamme, D. (1997). Development and validation of a body condition score system for dogs. Canine Practice.
- American Animal Hospital Association, Body Condition Scoring (BCS) Systems (descriptions of the 9-point scale). https://www.aaha.org/public_documents/professional/guidelines/weightmgmt_bodyconditionscoring.pdf