The free Pharm Pup formula sheet puts every dosage calculation formula a nursing student needs on two printable pages. Here is the same content as text; get the PDF for the printable version.
Formulas
| Use | Formula | Practice example |
|---|---|---|
| Any dose | Dimensional analysis | 250 mg × (5 mL ÷ 125 mg) = 10 mL |
| Tablets, mL | D/H × Q | 40 mg ÷ 20 mg × 1 tablet = 2 tablets |
| Pump rate | mL/hr = mL ÷ hr | 1,000 mL ÷ 8 hr = 125 mL/hr |
| Gravity drip | gtt/min = mL × drip factor ÷ min | 1,000 × 15 ÷ 480 = 31.25, so 31 gtt/min |
| Weight-based | dose = mg/kg × kg | 44 lb ÷ 2.2 = 20 kg; × 15 mg/kg = 300 mg |
| Infusion time | hr = mL ÷ mL/hr | 1,000 mL ÷ 125 mL/hr = 8 hr |
| Units/hr | units/hr = mL/hr × units/mL | 12 mL/hr × 100 units/mL = 1,200 units/hr |
| BSA (Mosteller) | √(cm × kg ÷ 3,600) | √(170 × 70 ÷ 3,600) = 1.82 m² |
Drip factors
Macrodrip: 10, 15 or 20 gtt/mL. Microdrip: 60 gtt/mL, where gtt/min equals mL/hr. Read the factor on the tubing package.
Conversions
1 g = 1,000 mg · 1 mg = 1,000 mcg · 1 L = 1,000 mL · 1 kg = 2.2 lb · 1 tsp = 5 mL · 1 tbsp = 15 mL · 1 oz = 30 mL · 1 hr = 60 min.
Rounding
Follow your school's rounding policy. Common rules: do not round until the last step; mL over 1 to the tenth, under 1 mL to the hundredth; gtt/min to the whole drop; tablets to the half only if scored. Leading zero always (0.5 mg), trailing zero never (5 mg, not 5.0 mg).
