Cat Benadryl Dosage Calculator
Use our cat Benadryl dosage calculator to estimate diphenhydramine dose from your cat’s weight. Get dose in mg plus liquid (12.4 mg / 5 mL), 25 mg tablets, and 12.5 mg chewables. For informational use only — confirm dosing with a veterinarian.
Can You Give Benadryl to a Cat?
Benadryl is a brand name for diphenhydramine, an antihistamine that veterinarians may use in cats for certain allergic reactions and itching. It can also cause drowsiness, which is why some owners ask about using it for sleep or to calm a cat down.
Do not self-dose without your vet. A cat’s safest dose depends on the reason for use, age, underlying health conditions, and other medications. Some products also contain additional ingredients that are unsafe for pets.
This calculator provides a weight-based estimate and then converts that estimate into common forms: liquid (12.4 mg / 5 mL), 25 mg tablets, and 12.5 mg chewable tablets.
Cat Benadryl Dosage Formula
Veterinary references commonly list diphenhydramine dosing in a range (mg per kg) and a typical frequency window. This calculator provides a simple estimate from weight and converts it into different forms. Always follow your veterinarian’s instructions.
A common rule-of-thumb is about 1 mg per lb. Many veterinary references also list 2–4 mg/kg (about 0.9–1.8 mg/lb) per dose, depending on the case.
Because 12.4 mg / 5 mL = 2.48 mg per mL.
This may be a decimal value depending on weight.
This may be a decimal value depending on weight.
Cat Benadryl Dosage Chart
Quick reference using the 1 mg per lb estimate. Liquid conversion uses 12.4 mg / 5 mL (2.48 mg/mL).
| Cat weight (lb) | Dose (mg) | Liquid (mL) | 25 mg tablets | 12.5 mg chewables |
|---|---|---|---|---|
| 5 | 5 | 2.02 | 0.2 | 0.4 |
| 7.5 | 7.5 | 3.02 | 0.3 | 0.6 |
| 10 | 10 | 4.03 | 0.4 | 0.8 |
| 12 | 12 | 4.84 | 0.48 | 0.96 |
| 15 | 15 | 6.05 | 0.6 | 1.2 |
| 18 | 18 | 7.26 | 0.72 | 1.44 |
| 20 | 20 | 8.06 | 0.8 | 1.6 |
How to Use This Calculator
- 1
Enter your cat’s weight (lb).
- 2
Read the estimated dose in mg.
- 3
Use the conversions shown for liquid (mL), 25 mg tablets, and 12.5 mg chewables.
- 4
If your vet has prescribed diphenhydramine, follow their dosing schedule (often referenced as every 8–12 hours in veterinary tables) and never exceed what they prescribed.
Frequently Asked Questions
Veterinarians may use diphenhydramine for certain allergic reactions and itching in cats. Whether it is appropriate depends on the cause of symptoms and your cat’s health, so ask your vet before dosing.
First find the estimated dose in mg. Then convert to liquid using the concentration. For 12.4 mg / 5 mL, that is 2.48 mg per mL, so mL = mg ÷ 2.48.
Diphenhydramine can cause drowsiness, but using it for sedation or calming should only be done if your veterinarian recommends it. It may not address the underlying cause of stress and can be risky in some cats.
Often, 25 mg is too much for many cats. The safest approach is to dose by weight and follow a veterinarian’s guidance, rather than giving a full tablet.
It can be dangerous if mis-dosed, if a cat has certain health conditions, or if the product contains other ingredients. If you suspect overdose or severe side effects, seek emergency veterinary care right away.