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Meters and millimeters ( and ) are commonly used metric measurements for length. The metric system is a decimal based system of measurement used by most countries across the world.^{[1] X Research source }The metric system is based on multiples of 10, so you can convert meters to millimeters and vice versa fairly quickly by multiplying and dividing.
Steps
Method 1
Method 1 of 2:Converting Meters to Millimeters
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1Find the number of whole meters you need to convert to millimeters. If this measurement is not given to you, you will need to measure using a meter stick or tape measure.
 The length of one meter stick is equal to 1 meter.
 A meter stick is NOT the same as a yardstick. There are 3 feet in a yard, but there are about 3.28 feet in one meter. ^{[2] X Research source }
 You will know a measurement is in meters because it will be labeled .
 For example, if the length of a floor is 4 meter sticks long, it is long.

2Find the number of partial meters you need to convert to millimeters. Often you will see meters stated in decimals. These means you have a partial meter to convert. If you are measuring, use the centimeter () or millimeter () units on the meter stick or tape measure.
 For example, if you measure something that is 4 meters long, plus 30 centimeters, it is 4.3 meters long, because there are 100 centimeters in 1 meter. ^{[3] X Research source }
 If you measure something that is 4 meters long, plus 30 millimeters, it is 4.03 meters long, because there are 1000 millimeters in a meter.^{[4] X Research source }
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3Write the number of meters, and place your pencil on the decimal point. To convert meters to millimeters you need to multiply. Since the metric system is based on multiples of ten, the easiest way to do this is by moving the decimal point to the right.^{[5] X Research source }
 For example, if you are converting , write and place your pencil on the decimal point.

4Move your pencil three places to the right. Since there are 1,000 millimeters per meter, you need to multiply by 1,000 to convert from meters to millimeters.^{[6] X Research source }
 For example, if your floor is long, you would move your pencil three decimal places to the right, adding two zeros to the number. This gives you .
 You could also use a calculator or use the standard multiplication algorithm to calculate .
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Method 2
Method 2 of 2:Converting Millimeters to Meters
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1Find the number of millimeters you need to convert to meters. If this measurement is not given to you, you will need to measure using a ruler.
 On a standard American ruler, millimeters can be measured with the smallest lines on the metric () side.
 Make sure you measure millimeters (small lines) and not centimeters (numbered lines).
 You will know a measurement is in millimeters because it will be labeled .
 For example, the length of a pencil might be long.

2Write the number of meters, adding a decimal to the right of the last digit. Place your pencil on the decimal point. To convert millimeters to meters, you need to divide. Since the metric system is based on multiples of ten, the easiest way to do this is by moving the decimal point to the left.^{[7] X Research source }
 For example, if you are converting , write and place your pencil on the decimal point.

3Move your pencil three places to the left. Since there are 1,000 millimeters per meter, you need to divide by 1,000 to convert from millimeters to meters.^{[8] X Research source }
 For example, if your pencil is long, you would move your pencil three decimal places to the left. This gives you .
 You could also use a calculator or use the standard division algorithm to calculate .
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Community Q&A

QuestionWhat do I do to convert m to mm?DonaganTop AnswererMultiply by 1,000.

QuestionHow do convert 1,27 mm into m?DonaganTop AnswererDivide mm by 1,000.

QuestionWhat is 1 meter + 85 cm + 400 mm?Community AnswerTo answer, you need to convert all of these to the same unit of measurement, for example, mm. There are 1000 mm in 1 m, and 10 mm in 1 cm. So the problem changes to 1,000mm + 850mm + 400mm.

QuestionHow do you convert mm into meters?DonaganTop AnswererDivide by 1,000.

QuestionHow would you convert 389 mm to m?Community AnswerSince there are 1,000mm in 1 m, you need to divide 389 by 1,000. You can do this simply by moving the decimal point three places to the left. So 389mm becomes .389m.

QuestionHow do you convert centimeters to meters?Community AnswerThere are 100 centimeters in 1 meter. To convert, divide the number of centimeters by 100.

QuestionHow do I convert 64 square meters into square millimeters?DonaganTop AnswererMultiply the number of square meters by one million.

QuestionHow do I convert ml to L?DonaganTop AnswererDivide by 1,000.

QuestionHow would I convert mm into km?DonaganTop AnswererMultiply by one million (1,000,000).

QuestionWhy do we divide when we change millimeters to meters?DonaganTop AnswererThere are fewer meters in a given length than there are millimeters. So when you convert any length from millimeters to meters, you're looking for a smaller number (because meters are longer than millimeters). So you divide, since division normally results in a smaller number  just as multiplying usually results in a larger number.
Tips
Things You'll Need
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References
 ↑ http://www.popsci.com/whyhasntusadoptedmetricsystem
 ↑ http://www.meterstofeet.com/
 ↑ http://mathcentral.uregina.ca/QQ/database/QQ.09.07/h/sherrie1.html
 ↑ http://ltcconline.net/greenl/courses/cahsee/geometry/units.htm
 ↑ http://www.purplemath.com/modules/metric.htm
 ↑ http://www.purplemath.com/modules/metric.htm
 ↑ http://www.purplemath.com/modules/metric.htm
 ↑ http://www.purplemath.com/modules/metric.htm
About This Article
To convert meters into millimeters, multiply the number of meters by 1,000. For example, if you have 5.2 meters, that would be 5,200 millimeters. Another way to get your solution is to write down the number of meters on a piece of paper. Then, simply move the decimal places over 3 places to the right. If you have 6.1 meters, that would become 6,100 millimeters after moving the decimal point. To learn how to convert millimeters into meters, scroll down!