Mass is a direct measure of the amount of matter in an object.

The SI unit of mass is the kilogram which is given the symbol kg .

Chemists in a laboratory usually deal with much smaller masses than kilograms, often grams or milligrams, so we need to be able to convert from one unit of mass to another.

Mass Conversions

SI Unit Conversions

factors

10^{12}

10^{9}

10^{6}

10^{3}

10^{2}

10^{1}

10^{-1}

10^{-2}

10^{-3}

10^{-6}

10^{-9}

10^{-12}

10^{-15}

10^{-18}

prefix

tera

giga

mega

kilo

hecto

deca

deci

centi

milli

micro

nano

pico

femto

atto

symbol

T

G

M

k

h

da

d

c

m

µ

n

p

f

a

1 kilogram (1kg) = 10^{3} grams (1000g)

1 gram (1g) = 1 ÷ 10^{3} kilograms = 0.001kg

1 milligram (1mg) = 10^{-3} grams (0.001g)

1 gram (1g) = 1 ÷ 10^{-3} milligrams = 1,000mg

1 microgram (1µg) = 10^{-6} grams

1 gram (1g) = 1 ÷ 10^{-6} micrograms = 10^{6}µg

Examples of Mass Conversions Using SI Units

Convert 1 kilogram to grams

From the table above we see that kilo = 10^{3} = 1,000
1 kg = 1,000 g

Convert 2.5kg to grams

1kg = 1,000 g
2.5 kg = 2.5 x 1,000g = 2,500 g

Convert 5 milligrams to grams

From the table above we see that milli = 10^{-3} 5mg = 5 x 10^{-3}g = 0.005g

Convert 250g to kilograms

1,000g = 1kg
1g = 1 ÷ 1,000 kg = 0.001 kg
250g = 250 ÷ 1,000 = 0.250 kg

Convert 25 µg to kilograms

1 µg = 10^{-6}g
25 µg = 25 x 10^{-6}g = 2.5 x 10^{-5}g

1g = 1 ÷ 1,000 kg
2.5 x 10^{-5}g = 2.5 x 10^{-5} ÷ 1,000 kg = 2.5 x 10^{-8}kg

Empirical Units of Mass

1 ounce = 0.0625 pounds = 28.35 grams

1 oz = 0.0625 lb = 28.35 g

1 pound = 16 ounces = 0.4536 kilograms

1 lb = 16 oz = 0.4536 kg

Examples of Conversion Between Empirical Units and SI Units of Mass

Convert 10 ounces to grams

1 oz = 28.35 g
10 oz = 10 x 28.35 g = 283.5g

Convert 2.5 pounds to kilograms

1 lb = 0.4536 kg
2.5 lb = 2.5 x 0.4536 kg = 1.134 kg

Convert 900 grams to pounds

1 lb = 0.4536 kg
and 1 kg = 1,000 g
so 1 lb = 0.4536 x 1,000 g = 453.6 g
so 1g = 1 ÷ 453.6 lb = 0.002205 lb

900g = 900 x 0.002205 lb = 1.9845 lb

Convert 0.25 pounds to milligrams

1 lb = 0.4536 kg
0.25 lb = 0.25 x 0.4536 kg = 0.1134 kg
and 1kg = 10^{3}g
So 0.1134 kg = 0.1134 x 10^{3} g = 113.4g