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Pharmacy unit converter

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Convert between pharmacy and clinical measurement units. Covers weight (mcg, mg, g, kg), volume (mL, L, tsp, tbsp, fl oz), concentration (mg/mL, %, mmol/L) and temperature (°C, °F, K).

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Pharmacy unit conversions: the ones that trip people up

Unit conversion errors are one of the leading causes of medication dosing mistakes. A 10-fold error from confusing mg with mcg, or mL with L, can be lethal. These are the conversions worth memorising and verifying every time.

Weight: the most common source of errors

1 gram = 1000 milligrams. 1 milligram = 1000 micrograms. So 1g = 1,000,000 mcg. A drug ordered as 0.5mg and dispensed as 0.5mcg delivers 1000 times less than intended. The reverse error (0.5mcg ordered, 0.5mg dispensed) delivers 1000 times more. Always confirm the unit before calculating. For drug doses in mcg: digoxin, fentanyl, levothyroxine, vitamin B12 injections. The Joint Commission's Do Not Use list flags the abbreviation "µg" itself as error-prone, since a handwritten µ is easily misread as an m, and recommends writing "mcg" in full instead.

Weight-based dosing compounds the error

Pediatric doses are commonly ordered in mcg/kg or mg/kg rather than a flat dose, which means a unit mix-up doesn't just miss the target by 1000-fold, it gets multiplied by the child's weight on top of that. Cross-check a weight-based mcg/kg or mg/kg order with our Pediatric Dosage Calculator before administering, particularly for anything ordered in micrograms.

Volume: household vs clinical measures

A US teaspoon = 5mL. A tablespoon = 15mL. A US fluid ounce = 29.57mL. Kitchen teaspoons vary by up to 40%, never use them to measure medication doses. Use an oral syringe or measuring cup calibrated in mL. The same principle applies to continuous infusions: rate is a volume-over-time calculation, so check our IV Drip Rate Calculator once you've confirmed the volume units on the bag and the order match.

Concentration: percent solutions

A 1% w/v solution contains 1g per 100mL, which equals 10mg/mL. Sodium chloride 0.9% = 9mg/mL = 154 mmol/L. Glucose 5% = 50mg/mL. Adrenaline 1:1000 = 1mg/mL. Adrenaline 1:10,000 = 0.1mg/mL. The 10-fold difference between these 2 adrenaline concentrations has caused fatal errors, which is why epinephrine appears on the ISMP List of High-Alert Medications. Always double-check the concentration on the ampoule label. For dilution and IV bag preparation calculations, use our Concentration Calculator.

Frequently asked questions

1 milligram (mg) = 1000 micrograms (mcg or µg). So 0.5mg = 500mcg, and 250mcg = 0.25mg. This conversion is clinically critical, confusing mg and mcg is one of the most common drug dose errors, particularly for digoxin, levothyroxine, fentanyl and vitamins.
1 US teaspoon = 5mL exactly (by pharmacopoeia definition). A tablespoon = 15mL. However, kitchen teaspoons vary by up to 40% from the standard 5mL volume. Always use an oral syringe or calibrated measuring cup for medication doses, never a kitchen spoon.
% w/v (weight/volume) means grams of solute per 100mL of solution. So 1% w/v = 1g/100mL = 10mg/mL. Normal saline (0.9% NaCl) = 0.9g/100mL = 9mg/mL = 154 mmol/L. Glucose 5% = 5g/100mL = 50mg/mL.