Dog & Cat Medication Dosage Calculator
One weight, every common over-the-counter medicine vets get asked about. Enter your pet's weight once and compare the published reference ranges, then take the numbers to your vet to confirm.
| Medicine | Reference range | For this weight |
|---|---|---|
| Benadryl diphenhydramine | 2–4 mg/kg | – |
| Zyrtec cetirizine | 0.5–1 mg/kg | – |
| Claritin loratadine | 0.25–0.5 mg/kg | – |
| Pepcid famotidine | 0.5–1 mg/kg | – |
| Imodium loperamide | 0.1–0.2 mg/kg | – |
| Dramamine dimenhydrinate | 4–8 mg/kg | – |
| Melatonin melatonin | weight bands | – |
| Tylenol acetaminophen | no home dose | Vet only |
| Ibuprofen ibuprofen | no home dose | Vet only |
| Aspirin aspirin | no home dose | Vet only |
Open each medicine for product strengths (tablets, mL), the forms to avoid, and the conditions where it should not be given. Confirm every dose with your vet.
Five rules before giving any human medicine to a pet
- Call your vet first. Even common medicines interact with heart, kidney, liver and thyroid conditions and with prescription drugs.
- Plain, single-ingredient products only. "-D", "Sinus", "Cold & Flu", "PM" and "Multi-Symptom" versions add decongestants, painkillers or sleep aids that can poison pets.
- Check for xylitol in liquids, chewables, gummies and melts.
- Never give human painkillers (acetaminophen, ibuprofen, naproxen, aspirin) unless your vet prescribes an exact dose.
- Cats are not small dogs. They lack liver enzymes that clear many drugs, so ranges for dogs do not transfer.
Questions owners ask
What human medicines are safe for dogs?
A few are commonly used by vets for dogs, including diphenhydramine (Benadryl), cetirizine (Zyrtec), loratadine (Claritin), famotidine (Pepcid) and sometimes loperamide (Imodium), but only in plain forms and at vet-approved doses. Painkillers such as acetaminophen, ibuprofen and naproxen are dangerous.
How do I convert my dog's weight to kg?
Divide pounds by 2.2. A 44 lb dog weighs 20 kg. The calculators accept either unit and convert automatically.
Can I use the dog doses for my cat?
No. Cats metabolise many drugs very differently. Only Benadryl has a cat page here; for anything else, ask your vet.