Order of Magnitude (Length)
Metric System units of Length
Yoctometers
So small. It’s equal to a septillionth of a meter. That means 1 septillion of these will equal 1 meter. Symbol is ym
Zeptometers
So Small. It’s equal to a sextillionth of a meter. That means 1 sextillion of these are equal to a meter. 1000 yoctometers in 1 zeptometer.Symbol is zm.
Attometers
Attometers are a quintillionth of a meter. So small. That means 1 quintillion of these is 1 meter. 1000 zeptometers or 1,000,000 yoctometers equal 1 attometer. Symbol is am.
Femtometers

A Femtometer is equal to 1 quadrillionth of a meter. That means 1 quadrillion of these is 1 meter. 1000 attometers,1,000,000 zeptometers or 1,000,000,000 yoctometers equal this femtometer.Symbol is fm.In the image you can see how small a femtometer is.
Picometers
A Picometer is 1 trillionth of a meter. That means 1 trillion of these is a meter (40 inches). 1000 femtometer,1,000,000 attometers,1,000,000,000 zeptometers, 1,000,000,000,000 yoctometers is a picometer. In the image. 1 Å = 100 pm.Symbol is pm.
Nanometers
A Nanometer is 1 billionth of a meter. That means 1 billion of these is a meter (40 inches). 1000 picometers,1,000,000 femtometers,1,000,000,000 attometers,1,000,000,000,000 zeptometers,1,000,000,000,000,000 yoctometers.Symbol is nm.
Micrometers
A Micrometer is 1 millionth of a meter. That means 1 million of these is a meter. 1000 nanometers, etc is a micrometer.The Symbol is um (I can’t get the right letter).100 micrometers (More expressed 100,000 nanometers is the thickness of a sheet of paper)
Millimeter
A Millimeter is 1 thousandth of a meter. It’s 1/10 of a centimeter.That means 1000 of these is 1 meter. You can see a millimeter. Symbol:mm.
Centimeter
A Centimeter is 1 hundredth of a meter, It’s 1/100 of a meter. A centimeter is the size of your finger. 2.5 centimeters (25 millimeters) is 1 inch.Symbol:cm.
Meter
A Meter is 1/1000 of a kilometer. It’s equal to around 40 inches. This is the base unit. It make sense to measure your height in cm or m.Symbol is m.
Kilometer
A Kilometer is 1000 meters, It’s 1/1000 of a megameter. This is used for long distances. Symbol is km. Some stuff above 1000 km (1 Megameter) is still used in kilometers.
Megameter
A Megameter is 1,000,000 meters. It’s 1/000 of a Gigameter and 1000 kilometers. A lot of people say 1000 kilometers rather than 1 megameter.Symbol:Mm
Gigameter
A Gigameter is 1 billion meters. It’s 1/1000 of a terameter and 1000 Megameters. Although people say 1,000,000 km instead of 1 Gm. Symbol is:Gm. 149.6 Gm is equal to the distance from the earth to the sun.
Terameter
A Terameter is 1 trillion meters. It’s 1/1000 of a petameter. 1000 Gigameters. Although people say 1 billion kilometers rather than 1 Tm. Symbol is Tm.
Petameter
A Petameter is equal to 1 quadrillion meters. It’s 1/1000 of a exameter. 1000 terameters. Although people say 1 trillion kilometers or use light years instead.Symbol is Pm.
Exameter
A Exameter is equal to 1 quintillion meters. It’s 1/1000 of a zettameter. 1000 petameters. Although people use light years or kilometers instead.Symbol is Em.
Zettameter
A Zettameter is equal to 1 sextillion meters. It’s 1/1000 of a yottameter and 1000 exameters = 1 zettameter. Although people use light years.Symbol is Zm.
Yottameters
A Yottameter is equal to 1 septillion meters. It is so big. 1000 zettameters is equal to 1 yottameter.Symbol is Ym.
Imperial Units of length
Inch
A inch is equal to 2.5 centimeters. It is 1/12 of a foot. It’s 1/36 of a yard. The symbol is in.
Foot
A Foot is 12 inches. It is 1/3 of a yard and 1/5280 of a mile. The symbol is ft.
Yard
A Yard is 36 inches or 3 feet. It is 1/1760 of a mile. The symbol is yd.
Mile
A Mile is 5280 feet or 1760 yards. The mile is equal to 1.6 kilometers. The symbol is mi.