Antibiotic Dose by Weight Calculator
Enter the patient weight and copy the exact prescription instruction (mg/kg/day or mg/kg/dose) to verify daily dose, dose per administration, and optional liquid volume (mL).
Use the Antibiotic Dose by Weight Calculator
Prescription Arithmetic Inputs
Copy the exact weight and dosing instructions from the prescriber or pharmacist label.
If the prescriber or label specifies an absolute daily cap.
Liquid Suspension Concentration (Optional)
Copy the active concentration exactly as printed on the pharmacy bottle (e.g. 250 mg in 5 mL).
Clinical Notice: This calculator performs purely mathematical arithmetic. It does not select antibiotics, verify clinical appropriateness, or replace professional judgment. Always verify the calculation, dosing device markings, and rounding increments with a licensed pharmacist or prescriber.
No calculations to display
Enter patient weight, prescribed dosing rate, and doses per day to calculate the mathematical dose.
Active Dose Arithmetic (mg)
Dose per Administration
mg / dose
Total Daily Dose
mg / day
Dosing Schedule
Calculated Weight Basis
kg
Liquid Oral Suspension Volume
Volume per Administration
mL / dose
Total Daily Volume
mL / day
Arithmetic Standards & Unit Factors
- Mass conversion: 1 kg = 2.2046226218 lb (unrounded precision preserved during calculation).
- Volume conversion: Liquid volume (mL) = mg dose × (label mL / label mg).
- Volume unit: Expressed strictly in millilitres (mL) per FDA safe-use guidance.
Summary
This tool performs mathematical verification of weight-based antibiotic instructions provided by a licensed prescriber or pharmacist. It does not select an antibiotic, suggest a dose, or verify clinical appropriateness. The user enters the exact weight, prescribed mg/kg instruction, dosing frequency, and optional bottle concentration (mg per mL) to check the arithmetic in milligrams and millilitres.
How it works
- Enter the patient weight in kilograms (kg) or pounds (lb). Pounds are converted using 1 kg = 2.2046226218 lb without premature rounding.
- Select the instruction format provided on the prescription: mg/kg/day divided into doses, or mg/kg/dose given a set number of times per day.
- Enter the prescribed rate (mg/kg) and the integer number of doses per day.
- Optionally enter a clinician-prescribed daily maximum (mg/day) to check whether the weight-based total reaches the cap.
- Optionally enter the oral liquid concentration exactly as printed on the bottle (X mg in Y mL) to calculate millilitres (mL) per dose and per day.
- Always measure oral liquids with the calibrated oral syringe or dosing cup supplied with the medication; household spoons must never be used.
Use cases
- Verify math for a pediatric prescription written as mg/kg/day divided into 2 or 3 doses.
- Verify math for an instruction written as mg/kg/dose given a specified number of times daily.
- Convert prescribed milligrams per dose into millilitres using the exact concentration printed on the pharmacy bottle.
- Check whether a calculated weight-based daily total reaches an entered prescriber daily maximum.
- Practice and double-check clinical arithmetic for pharmacology and nursing dosage calculations.