About Pet Sums

Pet Sums is a set of free calculators for dog and cat owners: age in human years, how big a puppy will get, how many calories and cups to feed, a pregnancy due date, and whether the chocolate your dog just ate is an emergency. Each one is built on a formula a veterinarian would recognise, and each page shows the arithmetic rather than asking you to trust a number.

Where the numbers come from

Calories use the resting energy requirement equation, RER = 70 × (weight in kg)^0.75, multiplied by the life-stage factors published in WSAVA and veterinary nutrition guidance. Dog age uses two published methods side by side: the 2020 UCSD epigenetic-clock formula (16 × ln(age) + 31) and the size-adjusted chart used by the AVMA and AKC. Cat age uses the AAFP/ISFM life-stage convention. Chocolate toxicity uses the theobromine content ranges and dose thresholds in the Merck Veterinary Manual. Gestation milestones follow Merck as well. Where a formula is a rule of thumb rather than a measurement -- puppy growth curves, for instance -- the page says so and shows the simpler rule beside it.

What this site doesn't do

It doesn't store what you enter, require an account, or replace your vet. A feeding amount from the RER formula is a starting point you adjust against your animal's body condition over a few weeks; a toxicity estimate tells you whether to pick up the phone, not whether to skip the call. If your pet is unwell, pregnant, or has eaten something it shouldn't, the right tool is a veterinarian.

Corrections

If you are a veterinarian or veterinary nutritionist and a formula, factor, or threshold here is out of date, email hello@petsums.com. Sources are named on each page so a correction can be checked against them.