Nursing conversions chart

How to convert without memorising directions

Every conversion is one equivalent written as a fraction, oriented so the unit you have cancels. To turn 0.75 g into mg, multiply by 1,000 mg / 1 g: the g cancel and 750 mg remains. To turn 154 lb into kg, multiply by 1 kg / 2.2 lb: 70 kg.

A check that always holds: a smaller unit means a bigger number. Milligrams are smaller than grams, so the number in mg is larger. Kilograms are larger than pounds, so the number in kg is smaller. If your result moved the other way, you multiplied where you should have divided.

Metric conversions you will use every shift

Metric steps between g, mg and mcg are always 1,000. Microgram doses appear for drugs such as levothyroxine, digoxin and fentanyl, and the decimal place matters: 0.125 mg is 125 mcg. Write mcg rather than the Greek µg, which is often misread as mg.

Volume is mL and L, also 1,000 apart. You will see cc in older references; 1 cc equals 1 mL, but cc is on the ISMP list of error-prone abbreviations, so write mL.

Household and apothecary measures

Household measures appear when teaching patients and in oral liquid questions: 1 tsp = 5 mL, 1 tbsp = 15 mL, 1 oz = 30 mL, 1 cup = 240 mL. Kitchen spoons vary, which is why patients are given an oral syringe or dosing cup marked in mL.

Grains are the one apothecary unit still tested. Programs use 1 gr = 60 mg, and some texts use 65 mg; use the value your instructor states, and the one the question gives if it gives one. Our conversions drill states which it uses.

Weight in kilograms

Weight-based doses always use kilograms. Divide pounds by 2.2, and keep the full value until the end of the dose calculation unless your program rounds weight first. 187 lb ÷ 2.2 is 85 kg; 165 lb is 75 kg. Using pounds as kilograms more than doubles the dose, and it is the error exam writers test most in weight-based questions.

Temperature and length

Temperature converts with a formula rather than a factor: °F = (°C × 1.8) + 32, and °C = (°F − 32) ÷ 1.8. A temperature of 38 °C is 100.4 °F. Length is rarely tested, but 1 in is 2.54 cm, which appears in pediatric height questions and body surface area calculations.

Time and the 24-hour clock

Medication records use the 24-hour clock: 0800 is 8 AM, 1400 is 2 PM and 2200 is 10 PM. Infusion questions that ask for a finish time expect the answer in the same format. An infusion of 1,000 mL at 100 mL/hr started at 0800 runs 10 hours and finishes at 1800.

Minutes convert to hours by dividing by 60, and fractions of an hour to minutes by multiplying by 60: 0.67 hr is about 40 minutes.

How exams test conversions

Few exams ask for a conversion alone. Conversions appear inside other problems: an order in grams against a label in milligrams, a weight in pounds for a mg/kg order, a time in minutes for a pump rate. That is why the conversion drill matters even when conversions look trivial on their own. Recognising when one is needed is the skill.

When a conversion is the whole question, it usually tests direction or the decimal place. Say the check aloud: smaller unit, bigger number.

Converting inside a dose problem

Most conversions you will do are a step inside a larger calculation, and the rule is to convert the order to the unit on the label. An order for 0.25 mg of digoxin with 125 mcg tablets becomes 250 mcg, and 250 ÷ 125 is 2 tablets. Converting the label instead, to 0.125 mg per tablet, gives the same answer but adds a decimal you can lose. Keep the label's unit and change the order.

Equivalents to know without looking

If you memorise only a few lines, make them these: 1 kg = 2.2 lb, 1 g = 1,000 mg, 1 mg = 1,000 mcg, 1 L = 1,000 mL, 1 tsp = 5 mL, 1 tbsp = 15 mL, 1 oz = 30 mL, 1 hr = 60 min. Every dosage exam assumes them, and most will not print them. The drill on this page cycles through all of them with real numbers, which is faster than flash cards because you also practise the direction.

Check before you submit

Did the number get bigger when the unit got smaller? Did you move the decimal three places for metric steps? Did you divide pounds by 2.2? Is the answer rounded the way the question asks, often exact for metric and to the tenth for weight? Those four checks catch nearly every conversion slip.