acalculator

Dog weight: is my dog overweight?

Enter your dog’s weight and body condition score. The dog weight calculator estimates the ideal weight and charts a safe weekly weight loss to reach it.

Your numbers

Units
Ideal weight (lb)
50

Ideal weight: about 50 lb (22.7 kg) for a 60 lb dog (Overweight).

Ideal weight (kg)kg
22.7
Body condition
Overweight
Over ideal weight
20%
Weight to loselb
10
Weight to lose (kg)kg
4.5
Weeks to ideal weight
19

Ideal weight (lb): 50. Ideal weight: about 50 lb (22.7 kg) for a 60 lb dog (Overweight).

Weight week by week

How to calculate

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.

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).

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.

  • 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.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Current weight 60 lb, Body condition score 7: overweight, Weight loss per week 1% gives Ideal weight (lb) 50, Ideal weight (kg) 22.679619, Over ideal weight 20%, Weight to lose 10, Weight to lose (kg) 4.535924, Weeks to ideal weight 19, Body condition 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. Current weight 66.14 lb, Body condition score 9: very obese, Weight loss per week 2% gives Ideal weight (lb) 47.241913, Ideal weight (kg) 21.428571, Over ideal weight 40%, Weight to lose 18.896765, Weight to lose (kg) 8.571429, Weeks to ideal weight 17, Body condition Obese.Source: Brooks et al. (2014), AAHA Weight Management Guidelines (BCS 9/9 is about 40% over ideal)
  3. Current weight 22 lb, Body condition score 6: above ideal, Weight loss per week 1.5% gives Ideal weight (lb) 20, Ideal weight (kg) 9.071847, Over ideal weight 10%, Weight to lose 2, Weight to lose (kg) 0.907185, Weeks to ideal weight 7, Body condition Above ideal.
  4. Current weight 55.12 lb, Body condition score 5: ideal, Weight loss per week 1% gives Ideal weight (kg) 25, Over ideal weight 0%, Weight to lose 0, Weight to lose (kg) 0, Weeks to ideal weight 0, Body condition Ideal.

How it works

Ideal weight. On the 9-point body condition score (BCS), 4 and 5 are ideal, and each point above 5 is about 10% over ideal weight: 6 is 10% over, 7 is 20%, 8 is 30% and 9 is 40%. So

ideal weight = current weight ÷ (1 + 0.1 × (BCS − 5)) = 10 × current weight ÷ (BCS + 5)

for a score of 5 to 9. At a score of 4 the dog is ideal already, so the ideal weight is the current weight.

  • Over ideal weight = 10% × (BCS − 5), and 0% for a score of 4 or 5.
  • Weight to lose = current weight − ideal weight.
  • Body condition: 4 or 5 Ideal, 6 Above ideal, 7 Overweight, 8 or 9 Obese.

Weeks to the ideal weight. Each week the dog loses the chosen percent r of its weight at the start of that week, so after n weeks it weighs

current weight × (1 − r ÷ 100)ⁿ

The weeks shown are the first whole number of weeks at which that weight is at or below the ideal weight: n = ln(ideal ÷ current) ÷ ln(1 − r ÷ 100), rounded up to a whole week (a value within 10⁻⁹ of a whole number counts as that whole number). At a score of 4 or 5 it is 0.

The chart draws the weight week by week, never below the ideal weight, in kilograms, and marks the week the goal is reached.

Rules

  • Current weight: 0.2 kg to 150 kg (0.44 lb to 331 lb).
  • Weight loss per week: 0.5% to 2%.
  • A score of 1 to 3 (underweight) gives no answer: "A score of 1 to 3 means your dog is underweight. This calculator is for dogs at or above ideal weight; ask your vet about a plan to gain weight."

What the calculator shows

  • The weight box is read as the exact decimal you typed in its unit (60 lb is exactly 60 × 0.45359237 kg). Ideal weight and weight to lose are exact from it, and each is shown in pounds (the exact kilograms ÷ 0.45359237) and in kilograms, rounded half up to at most one decimal place (trailing zeros are not shown: 50, not 50.0).
  • Over ideal weight as a whole percent.
  • Weeks to ideal weight as a whole number.

Worked examples by hand

A 60 lb dog with a score of 7, losing 1% a week. Ideal: 60 ÷ (1 + 0.1 × 2) = 60 ÷ 1.2 = 50 lb; 20% over; 10 lb to lose. Weeks: ln(50 ÷ 60) ÷ ln(0.99) = −0.18232 ÷ −0.01005 = 18.14, so 19 weeks.

A 30 kg dog with a score of 9, losing 2% a week. Ideal: 30 ÷ 1.4 = 300 ÷ 14 = 21.43 kg; 40% over; 8.57 kg to lose. Weeks: ln(1 ÷ 1.4) ÷ ln(0.98) = −0.33647 ÷ −0.02020 = 16.65, so 17 weeks.

A 22 lb dog with a score of 6, losing 1.5% a week. Ideal: 22 ÷ 1.1 = 20 lb; 10% over; 2 lb to lose. Weeks: ln(1 ÷ 1.1) ÷ ln(0.985) = 6.31, so 7 weeks.

A 25 kg dog with a score of 5. Ideal already: the ideal weight is 25 kg, 0 to lose, 0 weeks.

Other questions people ask

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.