PupCurve is a web based tool that provides a set of calculators for estimating puppy and dog adult weight, growth patterns, size classification, and pregnancy due dates, as well as a cat age calculator. The calculators are built on a dataset of 1.07 million real dog weigh ins drawn from a published study. Users enter a puppy’s age and current weight to receive a likely adult weight range with an 80 percent confidence interval. Additional weigh ins can be saved to refine the forecast over time, and a generated chart displays the growth curve and the tightening range. The tool includes six primary calculators: a puppy weight calculator, a puppy growth calculator for plotting multiple weigh ins, a dog weight calculator that provides an adult weight forecast along with a healthy weight range and daily calorie guidance, a dog size classifier (toy, small, medium, large, or giant), a dog pregnancy calculator that gives a due date window and week by week guide, and a cat age calculator that converts cat years to human years with life stage information. No user sign up is required to use any of the calculators. A typical workflow involves entering a puppy’s age and weight, viewing the predicted adult weight range, and then recording subsequent weigh ins to watch the range narrow. The tool also flags off curve growth, such as a puppy growing faster or slower than healthy dogs or losing weight, while there is still time to act. Feeding recommendations are based on the National Research Council growth equation, using current weight and predicted adult size. For breeders, a litter mode supports daily weigh ins for each pup, collar colour tracking, a first two weeks weight loss warning, and whelping checklists. Users can generate PDF summaries for veterinary visits and go home packets for puppy buyers. The calculators run in a browser and display their working and margin of error. The error reported is the gap between the forecast and the final adult weight expressed as a percentage of adult weight, tested on unseen dogs. Users can also access a puppy weight chart by age for reference.