How To Convert Metric Measurements

Convert from one metric unit of measure to another by moving decimal places.

The metric system of measurement is the most commonly used system in the world. The name "metric" comes from its basic unit of length---the meter. The metric system---like the decimal system---is based upon multiples of ten and uses specific prefixes to indicate multipliers of different base units.

Things You'll Need

• List of metric prefixes and their corresponding values

Instructions

1. Know the prefixes and their values, so you'll know whether you're converting up or converting down. Using weight as an example, note that "gram" is the base unit and some prefixes are "kilo-," "centi-," "deci-," etc. Since "kilo-"is a multiplier of 1000, a kilogram would be 1000 grams. Since centi- means 1/100th you would multiply your base unit by 1/100, which is the same as dividing it by 100; a centigram is equal to 0.01 grams.

2. Recognize the relationship between decimal places and their values. For example, 0.1 is the same as 1/10th, which is the same as dividing 1 by 10; 0.001 is the same as 1/1000, which is the same as dividing 1 by 1000. According to "Math and Dosage Calculations for Health Care" by Booth and Whaley, converting from one metric unit of measure to another is similar to multiplying and dividing decimals, and is easily accomplished by adhering to the following rules: "1) Move the decimal point to the right if you convert from a larger to a smaller unit, and 2) Move the decimal point to the left if you convert from a smaller to a larger unit." Add zeros as necessary.

3. Practice converting "down." For example, convert 5 kilograms (kg) to grams (g). You are converting from a larger unit (kg) to a smaller unit (g), therefore you will move the decimal place to the right. In this example, the decimal place wasn't written, but 5 is the same as writing 5.0. Because a kg is 1000g, you will move the decimal three places. This gives you exactly the same result as multiplying the 5 by the kilo- value of 1000. Therefore, 5kg = 5000g

4. Practice converting "up." Convert 500 milligrams (mg) to grams (g). Since you are converting from a smaller unit to a larger unit, you will move the decimal point to the left. Because a milligram is 1/1000th of a gram (0.001), you would move the decimal point three places. This is exactly the same as dividing 500 by 1000 (or multiplying by the milli- value of 1/1000). Therefore, 500mg = 0.5g

5. Practice converting between prefixes. Convert 500 micrograms (mcg) to milligrams (mg). As you are converting from a smaller unit (mcg) to a larger unit (mg), you will move the decimal point to the left. Because micro- = 1/1,000,000 and milli- = 1/1000, the difference between them is 1/1000 or three decimal places. Therefore 500mcg = 0.5mg, which is the same answer you would get from dividing 500 by 1000.

Tips & Warnings

• Prefixes and their values: kilo-= (1000), hecto-= (100), deka- (10), [base unit], deci- (1/10 or 0.1), centi- (1/100 or 0.01), milli- (1/1000 or 0.001), decimilli- (1/10,000 or 0.0001), centimilli- (1/100,000 or 0.00001), micro- (1/1,000,000 or 0.000001)

References

• Math and Dosage Calculations for Health Care. 3rd ed. 2010. Booth & Whaley, McGraw-Hill: Boston

Resources

• Read this Article in Spanish