Owners of an overweight pet usually want one thing from a plan: when will we get there? A date helps with motivation, with booking weigh-ins and with deciding when to move from loss to maintenance. It also invites false confidence, because a date implies a certainty that weight loss does not have. This guide shows how the date is calculated, compares two ways of doing the sum, gives a table for a 24 kg dog heading for 20 kg and explains how to treat the result as a planning aid rather than a deadline. Your vet sets the target weight, the daily calories and the pace; the arithmetic here only turns those choices into a calendar. The Pet Weight Goal Date Calculator does the sum.
The pace in the guidelines
The AAHA weight management guidelines describe a safe loss of about 1 to 2% of body weight per week. Our calculators use the same range. A pace below 1% a week is slow but can be right for some pets; a pace above 2% is too fast to recommend without veterinary supervision. For cats the pace and the plan are even more a matter for the vet.
Method 1: the straight-line estimate
This method assumes the same amount comes off each week, worked out from the starting weight.
weekly loss = current weight × weekly rate weeks to goal = (current − goal) ÷ weekly loss
For a 24 kg dog with a goal of 20 kg:
| Weekly rate | Weekly loss | Weeks to lose 4 kg | Goal date from 19 Oct 2026 |
|---|---|---|---|
| 1% | 0.24 kg | 16.7 | 13 February 2027 |
| 1.5% | 0.36 kg | 11.1 | 5 January 2027 |
| 2% | 0.48 kg | 8.3 | 17 December 2026 |
The dates round up to the next whole day. It is easy, and good enough for a first plan.
Method 2: the compounding estimate
In practice, a vet may set the pace as a percentage of the current weight at each weigh-in. As the pet gets lighter, the same percentage is a smaller amount, so the plan takes a little longer.
weeks to goal = ln(goal ÷ current) ÷ ln(1 − rate)
| Weekly rate | Straight-line weeks | Compounding weeks | Goal date (compounding) |
|---|---|---|---|
| 1% | 16.7 | 18.1 | 23 February 2027 |
| 1.5% | 11.1 | 12.1 | 12 January 2027 |
| 2% | 8.3 | 9.0 | 22 December 2026 |
The compounding method is about 8% longer here. It is the more realistic of the two when the plan is re-based on each weigh-in. Whichever you use, keep to one method for the whole plan so that dates are comparable.
Why the date is only an estimate
Real weight loss does not go in a straight line. Early weeks often show a larger drop, partly from water and gut content, and later weeks slow down. Several things move the date.
- The scale. A change of scale or method can make a week look better or worse.
- Treats and extras. A few extra calories each day add up; see how many treats a dog can have.
- Activity. A change in exercise changes the energy the pet uses.
- Illness or medication. Both can move weight.
- The goal itself. Your vet may revise the ideal weight as the pet changes shape.
Use the date to schedule weigh-ins, not to judge success. If the weight is on the planned track at a check-in, carry on. If it is ahead of the track, the pace may be too fast; if it is behind, recheck the amounts first.
Turning the date into checkpoints
A long plan is easier to follow in stages. Take the 24 kg dog at 1% a week with the straight-line method:
| Checkpoint | Week | Expected weight |
|---|---|---|
| Start | 0 | 24.0 kg |
| First check | 4 | 23.0 kg |
| Second check | 8 | 22.1 kg |
| Third check | 12 | 21.1 kg |
| Fourth check | 16 | 20.2 kg |
| Goal | 16.7 | 20.0 kg |
(Each step is 0.24 kg × weeks, rounded.) Weigh at each checkpoint on the same scale, in the same way; see how to weigh a dog at home. The Pet Weight Change Calculator turns two weights into the percentage and weekly pace so you can compare with the plan.
What the calories do
The goal date depends on the daily calories your vet sets. In our dog weight-loss calculator the starting figure is 1.0 × the resting energy requirement of the ideal weight. For a 20 kg ideal weight, RER = 70 × 20^0.75 = 662 kcal. A cat’s plan uses a factor of 0.8 × the RER of the ideal weight; for a 4 kg ideal weight that is 158 kcal. These are starting points to discuss with your vet; if the pet is not losing at the expected pace, the calories are reviewed, not simply cut. See the Dog Weight Loss Calculator and how many calories a dog should eat to lose weight.
After the goal
When the goal weight is reached, the plan changes from loss to maintenance. The daily calories rise to a maintenance level, and weigh-ins continue to catch any regain. The goal date is also the date to book a final check with the vet. Many pets regain if the end of the plan is treated as the end of care, so write the maintenance plan before you reach it.
A worked example
Ben’s dog weighs 24 kg and the vet has set a goal of 20 kg at about 1% a week. Ben uses the compounding method because the vet re-bases the plan at each check-up. 24 kg to 20 kg: ln(20 ÷ 24) = −0.1823; ln(0.99) = −0.01005; weeks = 18.1. From 19 October 2026 that is 18.1 × 7 = 127 days, so the goal date is 23 February 2027.
| Step | Working | Result |
|---|---|---|
| Weight to lose | 24 − 20 | 4 kg |
| Rate | 1% a week | |
| Straight-line weeks | 4 ÷ 0.24 | 16.7 |
| Compounding weeks | ln(20/24) ÷ ln(0.99) | 18.1 |
| Goal date | 19 Oct 2026 + 127 days | 23 February 2027 |
| Weigh-ins | every 4 weeks | 16 Nov, 14 Dec, 11 Jan, 8 Feb |
Ben puts the four weigh-in dates in his phone and a final vet visit in the week of 22 February. At the first weigh-in the dog is 23.1 kg, a little ahead of the compounding path, so the vet keeps the plan unchanged.
Recalculating as you go
The date should be recalculated at each weigh-in, from the new weight and the new date. If Ben’s dog is 23.1 kg after 4 weeks (16 November 2026), the straight-line sum from there is (23.1 − 20) ÷ (23.1 × 0.01) = 13.4 weeks, which gives a goal date of 18 February 2027, five days later than the original 13 February. A recalculated date is more useful than a fixed one, because it reflects what has happened.
| Weigh-in | Weight | Weeks left at 1% | Goal date |
|---|---|---|---|
| 19 Oct 2026 | 24.0 kg | 16.7 | 13 Feb 2027 |
| 16 Nov 2026 | 23.1 kg | 13.4 | 18 Feb 2027 |
A missed week
A week with no loss, or a week away from the plan, moves the goal by about a week. If the dog gains in a holiday week, the shift is a little more. The date is a rough guide, not a deadline, and the right response to a slip is to return to the plan and tell your vet if it keeps happening. Do not make up for a slow week by cutting food: a pace above the general range is the thing the plan is designed to avoid.
Common mistakes
- Treating the date as a deadline.
- Using a rate above 2% a week.
- Mixing the straight-line and compounding methods.
- Forgetting treats and extras.
- Changing the scale between weigh-ins.
- Cutting food sharply when behind.
- Having no plan for after the goal.
Quick summary
- Weeks to goal = (current − goal) ÷ (current × weekly rate), with 1 to 2% a week as the AAHA range.
- A 24 kg dog going to 20 kg takes 16.7 weeks at 1%, 11.1 at 1.5% and 8.3 at 2% (straight line).
- The compounding method is slightly longer: 18.1, 12.1 and 9.0 weeks.
- The date is a planning estimate; weigh every few weeks and adjust with your vet.
- Plan maintenance before you reach the goal.
- Use the Pet Weight Goal Date Calculator.
Frequently asked questions
How do I calculate a goal-weight date?
Divide the weight to lose by the weekly loss (current weight × rate). The result is the number of weeks; add it to today's date.
What weekly rate should I use?
The AAHA weight management guidelines describe about 1 to 2% of body weight a week. Your vet will choose the pace for your pet.
Why is the compounding method slower?
Each week's loss is a percentage of a smaller weight, so the weekly amount shrinks and the goal arrives a little later.
Is the date a promise?
No. It is a planning estimate. Real weight changes are uneven, and the plan should be adjusted from weigh-ins.
Does this work for cats?
The arithmetic is the same, but cats should lose weight under veterinary supervision, and the pace is set by the vet.
What if my pet stops losing?
Recheck the amounts and treats, weigh on the same scale, and talk to your vet. Do not cut food sharply on your own.
Sources
- AAHA (2014) Weight Management Guidelines for Dogs and Cats. Journal of the American Animal Hospital Association 50:1-11
- Pure arithmetic: straight line weeks = (current − goal) ÷ (current × rate); compounding weeks = ln(goal ÷ current) ÷ ln(1 − rate)
Related calculators
- Pet Weight Goal Date CalculatorEstimate the date a pet could reach its goal weight at a steady weekly loss, inside the 1–2% a week range.
- Pet Weight Change CalculatorTrack a weight change over time: percent change, percent per week and whether the pace is inside 1–2% a week.
- Dog Weight Loss CalculatorPlan a safe weight-loss target: daily calories and how many weeks it should take.
Keep reading
- How Fast Should a Dog Lose Weight?A safe pace for dog weight loss is about 1 to 2% of body weight a week. See kilograms per week, how long a goal takes, signs of losing too fast or too slowly.
- How Long Will It Take My Dog to Lose Weight?How long dog weight loss takes at 1% and 2% of body weight a week: a weeks-to-goal table, the formula behind it, why progress slows and how to track it.
- How to Track Your Pet's Weight ChangeHow to turn two weights into a percentage change and weekly pace, compare it with AAHA's 1 to 2% a week, read the trend and tell noise from real change.
- Dog Weight-Loss Weekly Check-In LogA weekly weigh-in log for a dog on a weight-loss plan: weight, change, percent per week, a six-week example averaging 1.04% a week, and what to do when off pace.