How this calculator works
Onions contain organosulfur compounds (such as N-propyl disulfide) that damage a dog’s red blood cells and can lead to oxidative hemolytic anemia. Commonly cited veterinary references note that clinically important effects can occur when a dog eats onion equal to roughly 0.5% of its body weight, which works out to about 5 grams of raw onion per kilogram of body weight.
This calculator divides the amount eaten by your dog’s weight to get a dose in grams per kilogram, then compares it to that 5 g/kg reference point as a percentage. Dehydrated onion products, such as onion powder found in some seasonings and broths, are far more concentrated by weight than fresh onion, so this tool applies a higher concentration factor for powder form to better reflect the amount of active compound consumed.
Cooking does not reliably remove the toxic compounds in onion, so cooked onion is treated the same as raw onion in this calculator.
This tool is for general educational and planning purposes only and does not replace professional veterinary advice. If your dog has eaten onion, especially in meaningful amounts or in concentrated form like powder, contact your veterinarian or an animal poison control hotline promptly.