How Long Will It Take My Dog to Lose Weight?

Quick answer At the AAHA pace of 1 to 2% of body weight a week, a dog needing to lose 20% of its weight takes about 12 weeks at 2% and 23 weeks at 1%. The weeks follow ln(goal ÷ current) ÷ ln(1 − rate), so loss slows as the dog gets lighter. Your vet should confirm the goal and the pace.

Every owner starting a diet with an overweight dog asks the same question: how long will this take? The honest answer is “a few months, and it depends”, but you can do better than that with some arithmetic. This guide shows how the time is worked out from the AAHA recommended pace, gives a table you can read off for dogs from 12 to 50 kg, explains why progress slows and shows how to track it so that the plan stays on course. It does not replace your vet, who should confirm the goal weight and the pace. For the safety side of pace, read how fast a dog should lose weight.

The pace everyone starts from

The AAHA 2014 weight management guidelines describe a safe rate of loss of about 1 to 2% of body weight per week. That is a percentage, not a fixed number of kilograms, so it shrinks as the dog gets lighter. A 30 kg dog losing 1% loses 300 g in the first week; when the dog weighs 26 kg, 1% is 260 g.

Because each week’s loss is a share of a lower weight, the weight follows a geometric pattern: after n weeks at rate r, the weight is the starting weight × (1 − r)^n. Solving for n gives the formula used by the Dog Weight Loss Calculator and the Pet Weight Goal Date Calculator:

weeks = ln(goal weight ÷ current weight) ÷ ln(1 − rate)

Rounded up to the next whole week. Try it for a dog that weighs 25 kg and should weigh 20 kg: ln(20 ÷ 25) = −0.223; ln(0.99) = −0.01005 and ln(0.98) = −0.0202. So the weeks at 1% are 0.223 ÷ 0.01005 = 22.2, which rounds up to 23, and at 2% they are 0.223 ÷ 0.0202 = 11.0, which rounds up to 12.

Weeks to goal for common starting points

Current weight	Goal weight	% to lose	Weeks at 1% a week	Weeks at 2% a week
12 kg	10 kg	16.7%	19	10
15 kg	12 kg	20.0%	23	12
20 kg	16 kg	20.0%	23	12
25 kg	20 kg	20.0%	23	12
30 kg	25 kg	16.7%	19	10
35 kg	28 kg	20.0%	23	12
40 kg	32 kg	20.0%	23	12
50 kg	40 kg	20.0%	23	12

Notice that the time depends on the percentage to lose, not the kilograms. A 50 kg dog and a 15 kg dog that each need to lose 20% have the same timeline, which surprises many owners. A giant breed needs to lose more kilograms, but at the same percentage rate the weeks are the same.

Which end of the range?

The difference between 12 and 23 weeks is large. Where should a dog sit between them? That is a decision for your vet, who will consider age, health, joints and how the dog responds. The slower pace is gentler, easier to stick to and often kinder to muscle. The faster end suits some dogs under supervision, but it leaves little room for error. Many owners choose a plan in the middle and adjust based on the weigh-ins.

If you know the weeks you need, you can also work backwards to a date. The Pet Weight Goal Date Calculator takes the start date, the weights and the rate and returns the goal date.

Why the plan slows down

Three effects make the last kilograms take longer than the first:

The percentage applies to a smaller number. In week 20 at 1%, a 25 kg dog’s loss is about 200 g, versus 250 g in week 1.
The calorie target falls as weight falls. Resting energy depends on weight to the power 0.75, so a lighter dog needs fewer calories, and the gap between intake and need narrows.
The body adapts. Weight loss usually slows after the first few weeks, and early losses may include water.

For these reasons, recalculate the daily calories every few weeks as the dog loses weight. The calculator uses the ideal weight for its calorie target, which is steadier, but your vet may stage the plan differently. See calories for dog weight loss for the arithmetic behind the target.

An example plan in stages

A 30 kg dog with an ideal weight of 25 kg, planned at 1.5% a week. The numbers are illustrations to show the stages.

Week	Expected weight (kg)	Change since start
0	30.0	0
4	28.2	−1.8
8	26.6	−3.4
12	25.0	−5.0
14	24.3	−5.7

At 1.5% a week the dog reaches 25 kg around week 12, as 30 × 0.985^12 = 25.0. If the dog loses less in some weeks, the line shifts right; there is no need to panic about one week’s reading. Write the expected line on a graph and plot actual weights against it every one or two weeks.

How to track progress

Weigh at the same time and on the same scale, ideally in the morning before breakfast.
Weigh every one to two weeks, not daily, since daily weights fluctuate.
Log the date, weight and food given.
Score body condition every few weeks with the Dog Body Condition Score tool. A change of one point on the 9-point scale is about 10% of weight.
Photograph the dog from above and from the side monthly.
Review with your vet at agreed points.

Our Pet Weight Change Calculator tells you whether the pace between two weights is inside the 1 to 2% range, which is a quick check when a week looks odd.

What if progress stops?

If the weight does not move for two to three weeks, check the usual suspects before changing anything: measuring errors, extra treats, food from family members and changes in activity. Our guide on why a dog is not losing weight is a checklist. If everything is accounted for and the dog still does not lose, ask your vet to review the plan and consider medical causes. Do not cut calories further without advice, since too low an intake risks nutrient shortfalls and muscle loss.

After the goal

Reaching the goal is not the end. Weight is easily regained, so plan the transition to maintenance with your vet: a gradual increase in food, continued monthly weigh-ins and an agreed range, such as the goal weight plus or minus a few percent. Keep treats within 10%, and stay with the exercise habits you built. Many owners find the first months of maintenance the riskiest, because the strict routine relaxes.

Common mistakes

Expecting a straight line.
Judging a week by one weigh-in.
Comparing kilograms instead of percentages.
Cutting calories hard to speed things up.
Not recalculating as weight falls.
Stopping the weigh-ins at the goal.

Questions to ask your vet

What is my dog’s goal weight?
What pace do you suggest for my dog?
How often should we weigh?
When should we recalculate the food?
How will we move to maintenance?

Setting milestones that feel achievable

A goal of 5 kg off may feel enormous. Break it into milestones of about 5% of the starting weight and celebrate each. For a 30 kg dog, 5% is 1.5 kg, so milestones fall at 28.5, 27.0, 25.5 and so on, depending on the goal. At 1% a week, each takes around five weeks; at 2%, around two to three. Each milestone gives a natural point to reweigh, rescore body condition, recalculate the food with the Dog Weight Loss Calculator and review the plan with your vet.

Milestone	Weight (30 kg start)	Rough weeks at 1% a week	Rough weeks at 2% a week
5% lost	28.5 kg	6	3
10% lost	27.0 kg	11	6
15% lost	25.5 kg	17	9
20% lost	24.0 kg	23	12

A note on puppies and seniors

Puppies are growing and should not be put on weight-loss diets without close veterinary supervision. Seniors may need slower plans because of joint and muscle concerns. These are cases where the percentage rule is only a starting point, and your vet’s plan comes first.

Worked example with a staged plan and re-planning

A 30 kg dog has a goal of 25 kg. The vet agrees a plan of about 1.5% a week, with checks every two weeks and a re-plan at the halfway point.

Check	Week	Planned weight	Actual weight	Action
Start	0	30.0	30.0	Begin; recalculate food from the goal weight
1	2	29.1	29.3	Slightly slow; check treats
2	4	28.2	28.5	Keep going
3	6	27.4	27.5	On track
4	8	26.6	26.9	Recalculate with the vet
5	10	25.8	26.0	Near the end
Goal	12 to 13	25.0		Move to maintenance plan

The actual weights sit a little above the plan, which is normal. The dog reaches 25 kg a week or so later than planned. A plan that allows for these small slips keeps everyone calm. At each check, compare with the plan, adjust by about 10% if the trend is off, and write down what you did.

Why the last kilogram is the hardest

As the dog nears the goal, the percentage rule produces smaller losses in grams, the dog’s energy needs have fallen and the owner’s enthusiasm may fall too. Prepare for it by planning a celebration of the milestones along the way, keeping the exercise routine fresh and agreeing with your vet when to stop dieting. Avoid reducing calories further to speed up the last part; it risks muscle loss. The plan ends when the dog reaches its goal and body condition, not when the calculator says so.

A reminder about vets and individuals

All of the arithmetic here describes averages and percentages. Your vet’s plan for your dog takes priority, and may differ for good reasons: age, joint health, other conditions or the dog’s response. Use the numbers to understand and to ask better questions.

Quick summary

The AAHA pace is about 1 to 2% of body weight a week.
Weeks = ln(goal ÷ current) ÷ ln(1 − rate); a 20% loss takes about 12 to 23 weeks.
Time depends on the percentage to lose, not the kilograms.
Loss slows as the dog gets lighter; recalculate calories every few weeks.
Weigh every one to two weeks and log progress.
Use the Pet Weight Goal Date Calculator to set a date.

Frequently asked questions

How long does it take a dog to lose weight?

Using the AAHA pace of 1 to 2% of body weight a week, a dog 20% above its goal takes about 12 to 23 weeks.

How is the time to goal calculated?

Weeks = ln(goal weight ÷ current weight) ÷ ln(1 − weekly rate). Each week's loss is a percentage of a smaller weight, so the pace in kilograms slows.

Why does my dog's weight loss slow down?

A fixed percentage of a lighter body is fewer grams, and the calorie target changes as weight falls. Recalculate every few weeks with your vet.

Is faster better?

Not necessarily. Losing faster than about 2% a week risks muscle loss and rebound. Your vet decides what is safe.

What is a realistic first goal?

Often a staged target, such as the first 10% of the total, then reassess. Your vet may set the stages.

How often should I weigh my dog on a diet?

Every one to two weeks, on the same scale, and log the results.

What if my dog is not losing weight at all?

Check measuring, treats and extras first, then ask your vet to review the plan and rule out medical causes.

Sources

Reviewed by the CalcuPaw Veterinary Review Team

Last reviewed 18 Oct 2026 · Meet the review team · This guide is general information, not veterinary advice.