Pet Medication Dosage Calculator — mg and ml by Weight
IMPORTANT—READ FIRST: This calculator does NOT replace a veterinarian. It's a reference tool to verify the dosage your vet already prescribed—useful if you're unsure about the ml or mg amount, your pet's weight has changed, or you need a refresher on administration instructions. Enter your pet's weight (kg), the prescribed dose (mg/kg) from the prescription or product insert, the drug concentration (mg/ml) shown on the label, and doses per day. It calculates total daily dose in mg, total daily volume in ml, and amount per dose in ml. Never give human medications to your dog or cat without explicit veterinary approval—common drugs like acetaminophen and ibuprofen are lethal to pets. If you don't have a prescription, don't use this calculator to guess—call your veterinarian or visit an emergency vet clinic.
To calculate pet medication dosage: multiply your pet's weight (kg) by the prescribed dose (mg/kg) to get the total mg. Then divide by the drug concentration (mg/ml) to get the ml to measure. Example: a 15 kg dog prescribed 10 mg/kg amoxicillin at 50 mg/ml suspension → 15 × 10 = 150 mg → 150 ÷ 50 = 3 ml per dose. **Always confirm with your vet before giving any medication.**
When to use this calculator
- Your vet prescribed an antibiotic and you want to double-check the exact ml amount before giving it.
- Your pet's weight has changed and you need to adjust a chronic medication dose.
- You have the product insert with mg/kg and the bottle concentration, but aren't sure how many ml to use.
- You're giving meloxicam or carprofen (NSAIDs) and want to verify the dosage one more time.
- Your pet's weight is atypical (e.g., a 2 kg kitten, a 60 kg giant breed dog) and the label doesn't cover it.
Real example: 15 kg dog prescribed amoxicillin by vet
- Pet weight: 15 kg.
- Prescribed dose (from vet): 10 mg/kg every 12 hours.
- Drug concentration (oral suspension): 50 mg/ml.
- Doses per day: 2 (every 12 hours).
- Dose per administration (mg):
15 kg × 10 mg/kg= 150 mg per dose. - Total daily dose (mg): 150 × 2 doses = 300 mg/day.
- Volume per dose (ml):
150 mg ÷ 50 mg/ml= 3 ml per dose. - Total daily volume (ml): 3 × 2 = 6 ml/day.
How it works
3 min readHow to Calculate Pet Medication Dosage
The Core Formula
Dose per administration (mg) = pet weight (kg) × prescribed dose (mg/kg)
Volume per administration (ml) = dose per admin (mg) ÷ drug concentration (mg/ml)
Total daily dose (mg) = dose per admin × doses per day
Total daily volume (ml) = volume per admin × doses per dayQuick Reference Table — Amoxicillin Suspension 50 mg/ml, 10 mg/kg, 2×/day
| Pet weight | Dose (mg/dose) | Volume (ml/dose) | Total/day |
|---|---|---|---|
| 2 kg (kitten/tiny dog) | 20 mg | 0.4 ml | 0.8 ml |
| 5 kg | 50 mg | 1.0 ml | 2.0 ml |
| 10 kg | 100 mg | 2.0 ml | 4.0 ml |
| 15 kg | 150 mg | 3.0 ml | 6.0 ml |
| 25 kg | 250 mg | 5.0 ml | 10.0 ml |
| 40 kg | 400 mg | 8.0 ml | 16.0 ml |
Change the concentration or mg/kg value to adapt for any drug.
⚠️ Important Warning
This calculator is a reference tool only and does NOT replace veterinary consultation. Before giving any medication:
1. Consult your veterinarian for the correct prescription.
2. Verify the dose in mg/kg on the prescription or product insert.
3. Check the concentration (mg/ml) on the medication label.
4. NEVER give human medication without explicit veterinary approval.
5. If your pet shows severe symptoms, go to an emergency vet clinic immediately—don't delay calculating a dose.
Common Veterinary Medications (Reference)
> Always with veterinary prescription. These are reference dosage ranges.
Antibiotics
| Medication | Typical Dose | Frequency | Use |
|---|---|---|---|
| Amoxicillin | 10–20 mg/kg | every 12 hrs | General bacterial infection |
| Amoxicillin + clavulanic acid | 12.5–25 mg/kg | every 12 hrs | Complex infections |
| Enrofloxacin (Baytril) | 5–20 mg/kg | every 24 hrs | Gram-negative, urinary |
| Metronidazole | 15 mg/kg | every 12 hrs | Diarrhea, giardia, anaerobes |
| Cephalexin | 15–30 mg/kg | every 12 hrs | Skin, urinary |
| Doxycycline | 5–10 mg/kg | every 24 hrs | Rickettsial, respiratory |
Anti-Inflammatories (NSAIDs) — Pain & Inflammation
| Medication | Dog Dose | Cat Dose | Frequency |
|---|---|---|---|
| Meloxicam (Metacam) | 0.1 mg/kg (day 1: 0.2) | 0.05 mg/kg | every 24 hrs |
| Carprofen (Rimadyl) | 2.2 mg/kg | NOT APPROVED | every 12 hrs |
| Firocoxib (Previcox) | 5 mg/kg | NOT APPROVED | every 24 hrs |
| Robenacoxib (Onsior) | 1–2 mg/kg | 1 mg/kg | every 24 hrs, up to 6 days |
Corticosteroids
| Medication | Anti-Inflammatory Dose | Use |
|---|---|---|
| Prednisone/Prednisolone | 0.5–1 mg/kg every 24 hrs | Allergies, inflammation |
| Dexamethasone | 0.1–0.2 mg/kg | Short-term only |
Stomach Protectants
| Medication | Dose | Use |
|---|---|---|
| Omeprazole | 0.5–1 mg/kg every 24 hrs | Ulcers, reflux |
| Famotidine | 0.5–1 mg/kg every 12 hrs | Gastritis |
| Sucralfate | 0.5–1 g every 8 hrs (dogs) | Ulcers |
Antiparasitic Medications
| Medication | Dose | Use |
|---|---|---|
| Ivermectin | 0.2 mg/kg (ONE-TIME DOSE) | ⚠️ AVOID in Collies, Australian Shepherds |
| Praziquantel | 5 mg/kg | Tapeworms |
| Pyrantel | 5 mg/kg | Internal parasites |
| Fluralaner (Bravecto) | 25 mg/kg | Fleas & ticks 3 months |
⚠️ Human Medications Toxic to Pets
These common human drugs are dangerous or lethal even in small doses:
| Medication | Toxicity | Why |
|---|---|---|
| Acetaminophen (Tylenol) | 🚨 LETHAL in cats (even small dose) | Cats lack proper liver enzymes |
| Ibuprofen | 🚨 TOXIC in dogs & cats | GI ulcers, kidney failure |
| Aspirin | TOXIC (except tiny doses in dogs) | Bleeding, ulcers |
| Naproxen | 🚨 HIGHLY TOXIC | Narrow safety window |
| Diclofenac | 🚨 TOXIC | Kidney failure |
| Xylitol (sweetener, gum, toothpaste) | 🚨 LETHAL | Severe hypoglycemia |
| Chocolate (theobromine) | TOXIC | Dark chocolate worse |
| Grapes/raisins | 🚨 TOXIC (dogs) | Acute kidney failure |
| Onions/garlic | TOXIC | Destroys red blood cells |
How to Administer Correctly
Liquid Oral Medications (Syrup/Suspension)
1. Shake the bottle well before measuring.
2. Draw exact dose into syringe (no needle).
3. Insert syringe at the side of the mouth (between molars and cheek, not down the center of tongue).
4. Inject slowly so your pet can swallow—don't force it.
Tablets / Pills
Signs of Overdose or Toxicity
🚨 Emergency—go to vet or call pet poison control if you see:
ASPCA Animal Poison Control: (888) 426-4435 (24/7).
Pet Poison Helpline: (855) 764-7661 (24/7).
Frequently asked questions
How do I calculate dog or cat medication dosage in ml from mg/kg?
Use the three-step formula: (1) Multiply your pet's weight in kg by the prescribed dose in mg/kg to get the total mg per dose. (2) Divide by the drug concentration in mg/ml to get the ml per dose. (3) Multiply by doses per day for the daily volume. Example: 10 kg dog, 10 mg/kg, 50 mg/ml suspension, twice daily → 10 × 10 = 100 mg → 100 ÷ 50 = 2 ml per dose → 2 × 2 = 4 ml/day.
Can I give my dog or cat ibuprofen or acetaminophen for pain?
NO. NEVER. Acetaminophen is LETHAL to cats even in one dose. It's also highly toxic to dogs. Ibuprofen causes severe stomach ulcers and kidney failure in both species. If your pet is in pain, take them to a vet—safe NSAIDs like meloxicam (Metacam) and carprofen (Rimadyl, dogs only) exist specifically for this. Never improvise with human over-the-counter pain relievers.
Do cats need different medication doses than dogs?
YES. Cats metabolize drugs very differently—they lack certain liver enzymes (glucuronyl transferase) that dogs have. Many dog medications are toxic to cats at equivalent doses. Even when the same drug is safe for both, the dose often differs: meloxicam for dogs is 0.1 mg/kg, but cats get 0.05 mg/kg (half). Always ask for a cat-specific prescription—never extrapolate from a dog's dose.
What if I miss a dose?
If you remember within 4 hours of the scheduled time, give it immediately and resume the normal schedule. If more than 4 hours has passed, skip that dose and give the next one on time. Never double up on a missed dose—this causes overdose, especially with NSAIDs (ulcers) or heart medications.
How do I verify my vet's dosage is correct?
Use the formula: dose_mg = weight_kg × mg/kg. If your vet wrote "150 mg every 12 hours for a 15 kg dog," that's 150 ÷ 15 = 10 mg/kg—reasonable for amoxicillin (10–20 mg/kg range). If the math looks way off (e.g., 500 mg for a 3 kg cat = 166 mg/kg—far too high), call your vet before giving it.
What if my pet vomits shortly after taking medication?
If vomiting occurs within 30 minutes and you see the pill in the vomit, contact your vet—the dose usually needs to be repeated. If it's been more than 2 hours, the medication likely absorbed, so don't repeat the dose. If vomiting is frequent (2+ times), call your vet urgently—it may be an adverse reaction.
Can I split a pill to give a smaller dose?
It depends. Pills with a center line/groove are designed to split. Never split: capsules (contents spill), enteric-coated tablets (acid-resistant coating breaks), extended-release pills (dumps full dose at once). Ask your vet or pharmacist. For small pets (kittens, tiny dogs), liquid suspensions allow exact ml dosing.
How long does liquid pet medication last once opened?
Usually 14 days refrigerated (2–8°C), but check the label. Amoxicillin suspension: 14 days. Clavamox: 10 days. Metronidazole: 30 days. Always read the package insert—expiration varies by drug. If the liquid changes color, separates oddly, or smells off, don't use it.
Can I stop antibiotics early if my pet seems better?
No. Finish the entire course. Your pet feels better by day 2–3 because weak bacteria die first. If you stop early, stronger, antibiotic-resistant bacteria survive and return. The minimum course is 7 days for most infections; 10–14+ days for urinary, skin, and chronic infections.
Which human medications are most dangerous for pets?
The deadliest: acetaminophen (lethal in cats), ibuprofen, naproxen, xylitol (artificial sweetener in gum and sugar-free treats), grapes/raisins, chocolate, onions, garlic, and alcohol. NSAIDs cause kidney failure and stomach ulcers. Xylitol causes sudden hypoglycemia—even a few grams can be fatal. When in doubt, call ASPCA Poison Control: (888) 426-4435.