How Dose Calculation Works
The core formula for liquid medication dosing is simple: divide the required dose by the available concentration to get the volume to administer.
| Common Medication | Typical Concentration | Common Dose |
|---|---|---|
| Amoxicillin suspension | 125 mg/5 mL (25 mg/mL) | 25–50 mg/kg/day |
| Ibuprofen suspension | 100 mg/5 mL (20 mg/mL) | 5–10 mg/kg/dose |
| Acetaminophen liquid | 160 mg/5 mL (32 mg/mL) | 10–15 mg/kg/dose |
| Metformin solution | 500 mg/5 mL (100 mg/mL) | 500–2000 mg/day |
Frequently Asked Questions
Divide the prescribed dose in mg by the concentration in mg/mL. For example: 250 mg prescribed, concentration 125 mg/mL — Volume = 250 / 125 = 2 mL. Simple, but always double-check with your pharmacist or prescriber.
Multiply the dose per kg by the patient weight in kg. A 10 mg/kg dose for a 20 kg child = 200 mg total dose. Then divide by concentration: if 100 mg/mL, you need 2 mL.
mg/mL stands for milligrams per milliliter — it expresses the concentration of a drug solution. A concentration of 50 mg/mL means 50 milligrams of active drug dissolved in every 1 milliliter of liquid.
Do not adjust the dose yourself. Contact your pharmacist — they can compound or advise on dose adjustments when the available concentration differs from what was prescribed.
IV medication dosing involves additional factors like rate of infusion and drip rates. This calculator handles single-dose volume calculation. For IV drip rate calculations, use a dedicated IV infusion calculator.
BID = twice daily (2 doses/day), TID = three times daily (3/day), QID = four times daily (4/day), QD or OD = once daily. Enter the frequency count in the doses per day field above.