Cat Benadryl Dosage Calculator
Enter your cat's weight to get the safe Benadryl (diphenhydramine) dose — in milligrams, tablets, or children's liquid. Includes a safety check before you dose.
Use your pet's current weight. Not sure? Round to the nearest pound.
Safety check — read before dosing
Enter a weight to see the dose.
Educational estimate only — not veterinary advice. Confirm the dose and suitability with your veterinarian before giving any medication.
How much Benadryl is safe for a cat?
Benadryl is the brand name for diphenhydramine, an antihistamine vets sometimes recommend for cats with mild allergic reactions, itching, or insect bites. The typical dose is about 1 mg of diphenhydramine per pound of body weight, every 8–12 hours. Because cats are small and sensitive, accurate measuring matters — the calculator above converts the dose into tablets or millilitres of children's liquid for your cat's exact weight.
Cats metabolise drugs differently from people and dogs. Only ever use plain diphenhydramine, never a "-D", "Sinus", or combination product, and never a product containing xylitol. When in doubt, call your vet first — this is especially important for kittens, pregnant cats, or cats with existing health conditions.
How this Benadryl dose is calculated
The standard veterinary dose of diphenhydramine for a cat is about 1.0 mg per pound (2.2 mg/kg) of body weight, given every 8–12 hours, up to 2× per day. We multiply your pet's weight by that rate, then divide by the strength of the product you selected to show the number of tablets or millilitres — rounded to an amount you can actually measure.
Benadryl dosage chart for cats by weight
A quick reference for common weights. Your pet's exact dose is shown by the calculator above.
| Cat weight | Dose (diphenhydramine) | Tablet |
|---|---|---|
| 5 lb | 5 mg | 0.25 tablets |
| 10 lb | 10 mg | 0.5 tablets |
| 15 lb | 15 mg | 0.5 tablets |
| 20 lb | 20 mg | 0.75 tablets |
| 25 lb | 24.9 mg | 1 tablet |
| 30 lb | 29.9 mg | 1.25 tablets |
| 40 lb | 39.9 mg | 1.5 tablets |
| 50 lb | 49.9 mg | 2 tablets |
| 60 lb | 59.9 mg | 2.5 tablets |
| 80 lb | 79.8 mg | 3.25 tablets |
| 100 lb | 99.8 mg | 4 tablets |
Doses shown for Tablet — 25 mg. Round to the nearest practical amount and confirm with your vet.
When not to give Benadryl
- Pets with glaucoma, cardiovascular disease, or hyperthyroidism without vet approval.
- Any product containing xylitol, decongestants (pseudoephedrine), or pain relievers (acetaminophen, ibuprofen).
Frequently asked questions
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