This is a convenient little chart I picked up somewhere. Simply follow the chart and it's simple to convert from one measurement to the other.

When you know:

inches
feet
yards
miles
centimeters
meters
kilometers
ounces
pounds
short tons
grams
kilograms
metric tons
fluid ounces
pints, US
pints, Imp.
quarts, US
quarts, Imp.
gallons, US
gallons, Imp.
mililiters
liters
liters
liters
liters
liters
liters

Multiply by:

25
30
0.9
1.6
0.4
1.1
0.6
28
0.45
0.9
0.035
2.2
1.1
30
0.47
.568
0.95
1.137
3.8
4.546
0.034
2.1
1.76
1.06
0.88
0.26
0.22

To find:

millimeters
centimeters
meters
kilometers
inches
yards
miles
grams
kilograms
metric tons
ounces
pounds
short tons
mililiters
liters
liters
liters
liters
liters
liters
fluid ounce
pints, US
pints, Imp.
quarts, US
quarts, Imp.
gallons, US
gallons, Imp.

Metric Conversion Chart