Dog Benadryl Dosage Calculator
Estimate a Benadryl (diphenhydramine) dose for your dog by weight, using the widely quoted 1 mg per pound guideline — shown in milligrams and standard 25 mg tablets.
Quick answer: The common guideline for dogs is about 1 mg of Benadryl (diphenhydramine) per pound of body weight, given 2–3 times a day. A 25 lb dog is roughly 25 mg — one standard tablet. Always confirm with your vet first.
Benadryl is a brand of diphenhydramine, an antihistamine that vets sometimes recommend for dogs with mild allergies, itching, or reactions to insect bites and stings. The usual guideline is around 1 mg per pound of body weight, up to three times a day — but the safe choice always depends on your dog and should be confirmed with a vet first.
How the dose is worked out
25 mg tablets = dose ÷ 25 · Children's liquid (12.5 mg/5 mL) = dose ÷ 2.5 mL
Worked example
A 25 lb dog: about 25 mg per dose, which is one 25 mg tablet, given 2–3 times a day. A 50 lb dog would be about 50 mg (two tablets), and a 10 lb dog about 10 mg — where the children's liquid or a smaller-strength tablet is easier to measure accurately.
Important safety points
Only plain diphenhydramine should be used — avoid "Benadryl" combination products that also contain decongestants (like pseudoephedrine) or paracetamol/acetaminophen, which are dangerous to dogs. Don't give Benadryl to a dog with certain conditions (such as glaucoma or heart disease) without veterinary guidance, and never apply this calculator to cats. If your dog is having a serious allergic reaction — swelling of the face or throat, difficulty breathing — treat it as an emergency and get to a vet immediately.