Basic Units and Terms

Prefix Prefix
Letter
Value (base 10) Value (base 2)
Kilo k (base 10)
K (base 2)
103 = 1,000 = 1 thousand 210 = 1,024
Mega M 106 =1,000,000 = 1 million 220 = 1,048,576
Giga G 109 = 1,000,000,000 = 1 billion 230 = 1,073,741,824
Tera T 1012 = 1,000,000,000,000 = 1 trillion 240 = 1,099,511,627,776
Peta P 1015 = 1,000,000,000,000,000 = 1 quadrillion 250 = 1,125,899,906,842,624
Exa E 1018 = 1,000,000,000,000,000,000 = 1 quintillion 260 = 1,152,921,504,606,846,976
Zetta Z 1021 = 1,000,000,000,000,000,000,000 = 1 sextillion 270 = 1,180,591,620,717,411,303,424
Yotta Y 1024 = 1,000,000,000,000,000,000,000,000 = 1 septillion 280 = 1,208,925,819,614,629,174,706,176

Prefix Prefix
Letter
Value (base 10) Distance Light Travels
Milli m 10-3 = 0.001 = 1 thousandth 186 miles
Micro μ 10-6 = 0.000001 = 1 millionth 327 yards
Nano n 10-9 = 0.000000001 = 1 billionth 11.8 inches
Pico p 10-12 = 0.000000000001 = 1 trillionth 0.01 inches
Femto f 10-15 = 0.000000000000001 = 1 quadrillionth 1/10 of the way across E.coli
Atto a 10-18 = 0.000000000000000001 = 1 quintillionth 3 hydrogen atoms
Zepto z 10-21 = 0.000000000000000000001 = 1 sextillionth about 100 atomic nuclei
Yocto y 10-24 = 0.000000000000000000000001 = 1 septillionth 1/10 of the way across an atomic nuclei

Some common usages:

Memory (RAM and Disk)
1 Kbyte = 1,024 bytes (appox. 1 thousand)
1 Mbyte = 1,048,576 bytes (appox. 1 million)
1 Gbyte = 1,073,741,824 bytes (appox. 1 billion)
1 Tbyte = 1,099,511,627,776 bytes (appox. 1 trillion)

Clock Speed
1 kHz = 1 KiloHertz = one thousand cycles per second
1 MHz = 1 MegaHertz = one million cycles per second
1 GHz = 1 GigaHertz = one billion cycles per second

Cycle Time
1 msec = 1 millisecond = 10-3 seconds per cycle
1 μsec = 1 microsecond = 10-6 seconds per cycle
1 nsec = 1 nanosecond = 10-9 seconds per cycle
1 psec = 1 picosecond = 10-12 seconds per cycle

Relationships
1 kHz clock speed is equivalent to a 1 msec cycle time
1 MHz clock speed is equivalent to a 1 μsec cycle time
100 Mhz clock speed is equivalent to a 10 nsec cycle time
1 GHz clock speed is equivalent to a 1 nsec cycle time

Powers of two:

21 = 2 25 = 32 29 = 512 213 = 8,192
22 = 4 26 = 64 210 = 1,024 214 = 16,384
23 = 8 27 = 128 211 = 2,048 215 = 32,768
24 = 16 28 = 256 212 = 4,096 216 = 65,536