By Alex Baer · Updated July 2026
Your dog turns seven and the internet tells you two things at once: buy senior food, and feed less. Neither instruction comes with a number, so most owners do one, both, or neither, and hope the dog looks about right.
The math is smaller than the advice. When our calculator decides a dog is a senior, exactly one thing changes: the activity multiplier is replaced by a flat 1.2. The calorie floor underneath it, RER = 70 × kg0.75, does not move at all. For a typical neutered adult on the moderate factor of 1.4, that is a drop of about 14 percent, and nothing about it depends on what the bag says.
What the bag says turns out to matter anyway, and not the way the marketing implies. The 18 senior formulas in our database average about 14 percent fewer calories per cup than the adult formulas. Your dog needs 14 percent less. The two numbers cancel, so the scoop after a switch can look identical to the scoop before it, while the calories underneath are finally correct. Change the food and cut the cups and you have made the same cut twice.
the drop in daily calories when a moderately active adult dog becomes a senior in the math: 1,018 kcal to 873 kcal for a 50 lb dog, about a third of a cup a day
Where the senior number comes from
Every portion on this site starts at the same place, the resting energy requirement: RER = 70 × (weight in kg)0.75. That is what the body burns doing nothing, and age does not change it. Daily calories are RER multiplied by a life factor, and the life factor is the only thing that moves.
Our calculator switches a dog to the senior factor at 7 years (84 months), and earlier, at 5 years, for giant breeds, which age faster. That cutoff is a modelling choice, not a diagnosis: nothing happens to your dog on its seventh birthday, and a bright, busy nine year old is not obliged to eat like a couch cushion. It is a default that is closer to right than the alternative for most dogs of that age.
The senior factor is 1.2, and it replaces the adult activity factor rather than stacking with it. So the cut you owe your dog is not a fixed number, it is the distance from where you already were:
- fed as a low-activity adult (1.2): nothing changes, you were already there
- fed as a moderate adult (1.4), the common case: about 14 percent fewer calories
- fed as a high-activity or intact adult (1.6): 25 percent fewer calories
That is the whole model. Everything below is arithmetic on top of it, plus the one thing the formula cannot see: the label on the bag you actually pour from.
Senior portion check
Set your dog's weight and how it was fed as an adult. The checker shows the new daily calories, the new scoop, and what the change is worth in a month.
For the full picture by breed, age, and real foods with prices, use the calculator.
Estimates only, not veterinary advice. Senior factor 1.2, the same one the calculator applies from age 7, or 5 for giant breeds. Monthly figures use the median dry-food price in our database, $1.85 per 1,000 kcal.
| Dog weight | Adult, moderate (×1.4) | Senior (×1.2) | Daily cut | Cups, same adult food (397 kcal/cup) | Cups, median senior food (350 kcal/cup) | Senior food bill |
|---|---|---|---|---|---|---|
| 15 lb | 413 kcal | 354 kcal | 59 kcal | 1.0 → 0.9 | 1.0 | $20 / month |
| 35 lb | 779 kcal | 668 kcal | 111 kcal | 2.0 → 1.7 | 1.9 | $37 / month |
| 50 lb | 1,018 kcal | 873 kcal | 145 kcal | 2.6 → 2.2 | 2.5 | $48 / month |
| 65 lb | 1,240 kcal | 1,063 kcal | 177 kcal | 3.1 → 2.7 | 3.0 | $59 / month |
| 100 lb | 1,713 kcal | 1,468 kcal | 245 kcal | 4.3 → 3.7 | 4.2 | $81 / month |
Calories: RER = 70 × kg0.75, times 1.4 as a moderately active neutered adult and 1.2 as a senior. Cups use the median density of our database, 397 kcal per cup for adult dry food and 350 for senior formulas. Food bill at the median dry-food price, $1.85 per 1,000 kcal. Read the two cup columns side by side: the calories fall, the scoop does not, if you also change the bag.
What the senior bag actually is
Start with what it is not. AAFCO, whose statement of nutritional adequacy appears on every complete-and-balanced bag in the United States, publishes two nutrient profiles: growth and reproduction, and adult maintenance. There is no senior profile. A dog food labelled for seniors is, formally, an adult maintenance food with a marketing word on the front, and the manufacturer decides what that word means.
So we read the labels instead. Our database holds 18 dry formulas sold for senior or "7+" dogs, and they behave like a category only in one respect:
- Calorie density: median 350 kcal per cup, against 409 for adult formulas. Senior bags are about 14 percent lighter per cup, which is almost exactly the calorie cut a senior dog is owed. That is the coincidence behind the unchanged scoop.
- Everything else is brand spread. Density runs from 308 kcal per cup for Royal Canin Large Aging 8+ to 427 for Orijen Senior, a 39 percent gap between two bags with the same word on them. Protein runs from 18 percent to 38 percent.
- There is no senior price premium. Across the 14 senior formulas we have prices for, the cost of 1,000 kcal runs from $1.04 for Iams Healthy Aging to $2.97 for Royal Canin Small Adult 8+, which is the same spread we see across the rest of the catalogue. Whatever you pay extra for, it is the brand, not the age on the label.
Which leaves the practical question. If you keep your dog on its adult food, the calorie cut has to come out of the scoop: about a third of a cup a day for a 50 lb dog. If you switch to a senior formula, some of the cut arrives inside the bag, in the form of fewer calories per cup, and the correct new scoop may be very close to the old one. The label tells you which case you are in. The word on the front does not.
The formula starts the conversation, the scale ends it
A formula is a starting point, and 1.2 is one flat assumption standing in for every dog over seven: the retired sprinter and the one who still hikes on Saturdays get the same multiplier, which cannot be right for both. The number gets you to a sensible portion in one step; the scale and the ribs tell you whether it landed. Weigh the dog monthly, adjust in small steps of five to ten percent, and trust the trend over any calculator, including ours. One thing the arithmetic explicitly cannot do: an older dog that is eating less, or losing weight on a portion that used to be right, is not a math problem. That is the visit to the vet, and it is worth making early.
Frequently asked questions
When is a dog considered a senior?
In our calculator, at 7 years old, and at 5 for giant breeds, which age faster. That is a modelling cutoff, not a diagnosis: it is the age at which feeding a dog like a moderately active adult starts to be wrong more often than it is right, so the multiplier drops to 1.2. Your dog does not become a different animal on its birthday, and an active nine-year-old may genuinely still need the adult number. Use the cutoff as the default, then let the scale settle the argument over the next couple of months.
Do I need to switch to senior dog food?
Not because of the age on the label. There is no AAFCO senior nutrient profile, so a senior food is an adult maintenance food that the brand has aimed at older dogs, and the recipes behind the word vary wildly: in our database senior formulas span 308 to 427 kcal per cup and 18 to 38 percent protein. What a senior bag reliably gives you is lower calorie density, a median of 350 kcal per cup against 409 for adult food, which is one convenient way to feed 14 percent fewer calories without shrinking the scoop your dog is used to. Staying on the adult food works exactly as well, as long as you take the calories out of the portion instead. If your dog has a medical reason to change diet, that decision belongs with your vet, not with a formula.
My senior dog is eating less. Should I be worried?
Start with the vet, not the calculator. Weight loss in an older dog, or a sudden lack of interest in a bowl that used to be emptied in seconds, is a clinical signal, and no arithmetic on this page can tell you what is behind it. The formula only answers a narrower question: how many calories the portion is supposed to deliver if nothing is wrong. Once your vet has ruled out a medical cause, the levers are ordinary ones, a more calorie-dense food so the same appetite carries more energy, or smaller meals more often, and the target number stays the one the math gives you.
The short version
- Age changes one number: the activity factor is replaced by a flat 1.2. The RER formula, 70 × kg0.75, does not move.
- The cut depends on where you started. From the common moderate factor of 1.4 it is about 14 percent: a 50 lb dog goes from 1,018 to 873 kcal a day, roughly a third of a cup.
- Our calculator flips a dog to senior at 7 years, and at 5 for giant breeds. It is a default, not a diagnosis.
- "Senior" is not a nutrition standard. AAFCO has no senior profile, and the 18 senior formulas we track run 308 to 427 kcal per cup and 18 to 38 percent protein.
- What senior bags do share is lower density: 350 kcal per cup against 409 for adult food, about the same 14 percent. Switch the bag and the correct scoop barely changes; stay on the adult bag and the scoop has to shrink.
- Do not make the cut twice. New food plus a smaller scoop, by reflex, leaves a 50 lb dog 12 percent under its target.
- There is no senior price premium: $1.04 to $2.97 per 1,000 kcal, the same spread as the rest of the catalogue.
More guides: How much should I feed my dog? · Feeding after spay or neuter · Why the feeding chart on the bag overfeeds your dog · Price per 1,000 kcal · How to switch dog food