Daily calorie needs vary by weight, life stage, activity, and physiological state. BreedCalc calculates RER = 70 × body weight in kg^0.75, then applies one selected MER factor rather than compounding multiple percentages. For example, the starting estimate for a 30 lb moderately active neutered adult dog is about 694 kcal/day.

Cat calorie needs depend on weight, life stage, lifestyle, and physiological state. The calculator selects one MER factor for these inputs and does not multiply diet type or breed percentages into the calorie target. The result is a starting estimate that should be adjusted by monitoring body weight and body condition.

Results are based on the NRC 2006 Resting Energy Requirement formula and WSAVA guidelines, using published MER starting factors listed in our Scientific Sources. They provide a clinically-aligned starting point, but individual variation (metabolism, environment, health conditions) means you should consult your vet for a final feeding plan. See our Methodology page for full details on the calculation.

The calculator uses neuter and overweight status to select an appropriate published starting factor. Diabetes, kidney disease, and underweight status do not apply automatic percentage changes because pets with medical conditions require an individual feeding plan from their veterinarian.

The old "multiply by 7" rule is scientifically inaccurate. Our breed age calculator uses breed-specific aging curves based on veterinary research. Small breeds (under 20 lbs) age much slower than giant breeds (over 100 lbs). A 5-year-old Chihuahua is roughly 36 in human years, while a 5-year-old Great Dane is about 45. Mixed breed dogs are calculated based on their weight category. This dog age calculator also accounts for the accelerated aging in the first 2 years of life.

Cats age rapidly in their first two years: year 1 equals roughly 15 human years, and year 2 adds about 9 more. After that, each cat year adds approximately 4 human years. A 5-year-old cat is about 36 in human years. Our age calculator currently includes 12 published cat profiles.

Research suggests larger dogs age faster at the cellular level. Giant breeds like Great Danes have average lifespans of 7–10 years, while small breeds like Chihuahuas may live 14–18 years. The exact mechanisms are still being studied, but accelerated growth rates and higher oxidative stress in large breeds are leading theories. This size-lifespan relationship is factored into our breed-specific aging curves.

Our breed weight calculator (also called a breed size calculator) predicts a puppy's adult weight based on their breed, current age, and current weight. It uses breed-specific growth curves to estimate final adult size. Small breeds reach adult weight by 10–12 months, medium breeds by 12–16 months, and giant breeds may continue growing until 18–24 months. The current site publishes 20 dog profiles; weight predictions remain estimates based on size and growth data.

Accuracy improves as your puppy gets older, because a larger proportion of their growth is already measured. At 4 months, predictions for a known breed are typically within 10–15% of the actual adult weight. By 6–8 months, accuracy improves to within 5–10%. Purebred dogs with well-established growth curves tend to have the most accurate predictions. Mixed breeds show wider natural variation.

Dog pregnancy (gestation) typically lasts 58–68 days, with an average of 63 days from ovulation. Our breeding calculator helps track important milestones including heat cycles, optimal breeding dates, expected whelping date, and puppy development stages week by week. Cat pregnancy is shorter at 58–67 days (average 65 days).

Enter your dog's breed and the mating date, and the calculator provides a complete week-by-week gestation timeline with key milestones: embryo implantation (day 19–21), heartbeat detection by ultrasound (day 25), sex determination (day 35), and expected whelping date (day 63). Most female dogs come into heat twice a year, with the fertile period typically 9–14 days after the start of estrus.

Yes! All four breed calculators (calorie, age, weight, and breeding) are 100% free to use with no sign-up required. We currently publish 20 dog profiles and 12 cat profiles. You can run unlimited calculations — all completely free.

BreedCalc currently publishes 20 dog profiles. This includes popular breeds like Labrador Retriever, German Shepherd, Golden Retriever, French Bulldog, Poodle, Beagle, Rottweiler, Dachshund, and Yorkshire Terrier, as well as rare breeds and designer crossbreeds (Goldendoodle, Labradoodle, Cockapoo, Bernedoodle, etc.). We also support mixed breed dogs in four size categories.

We currently publish 12 cat profiles. This includes Domestic Shorthair, Maine Coon, Siamese, Persian, Ragdoll, Bengal, British Shorthair, Abyssinian, Scottish Fold, Sphynx, and many more. Each cat breed has specific metabolism data, indoor/outdoor activity adjustments, and breed-typical weight ranges.

Yes. Mixed-breed dogs are calculated based on their weight category (small, medium, large, giant) using generalized factors. If you know one or both parent breeds, you can select the closest match for more specific results. The calorie and age calculators both support a "Mixed Breed" option with size-based calculations.

Our primary sources are the NRC Nutrient Requirements of Dogs and Cats (2006), WSAVA Global Nutrition Guidelines, AAHA Canine Life Stage Guidelines (2019), AAFCO nutrient profiles, FEDIAF nutritional guidelines, and peer-reviewed aging research. See our full Scientific References page for complete citations.

We currently offer dedicated age calculators for Holland Lop Rabbits, Guinea Pigs, Cockatiels, and Ferrets. Calorie calculations focus on dogs and cats. We plan to expand exotic-pet coverage over time — check our Blog for updates.