SI Prefixes: How Many Watts in a Kilowatt and Kilowatts in a Megawatt

SI prefixes are very important in electrical engineering but also in everyday life. Their use is relatively easy, but it can also cause many problems when done incorrectly.

Watts to kilowatts, kilowatts to megawatts, and other conversions are very important when electric energy and power of electric motors, pumps, winches, inverters, batteries, and other devices are being calculated, planned, transferred, or being used. SI prefixes help significantly, especially when dealing with very large or very small values.

watts to kilowatts

Standard SI Prefixes

SI prefixes are used in order to write down a very large or very small numbers - after all, it is much easier to write, for example, 25 kW than 25000 watts. But, it is also much easier to write 25 MW than 25000 kW or 25000000 watts.

The following chart lists the International System of Units (SI) official prefixes:

Prefix Base 10 Decimal English Word
Name Symbol Short Scale Long Scale
yotta Y 1024 1 000 000 000 000 000 000 000 000 septillion quadrillion
zetta Z 1021 1 000 000 000 000 000 000 000 sextillion trilliard
exa E 1018 1 000 000 000 000 000 000 quintillion trillion
peta P 1015 1 000 000 000 000 000 quadrillion billiard
tera T 1012 1 000 000 000 000 trillion billion
giga G 109 1 000 000 000 billion milliard
mega M 106 1 000 000 million
kilo k 103 1 000 thousand
hecto h 102 100 hundred
deca da 101 10 ten
- - 100 1 one
deci d 10-1 0.1 tenth
centi c 10-2 0.01 hundredth
milli m 10-3 0.001 thousandth
micro μ 10-6 0.000 001 millionth
nano n 10-9 0.000 000 001 billionth milliardth
pico p 10-12 0.000 000 000 001 trillionth billionth
femto f 10-15 0.000 000 000 000 001 quadrillionth billiardth
atto a 10-18 0.000 000 000 000 000 001 quintillionth trillionth
zepto z 10-21 0.000 000 000 000 000 000 001 sextillionth trilliardth
yocto y 10-24 0.000 000 000 000 000 000 000 001 septillionth quadrillionth

Note: the 'Short Scale' is in use in, for example, the United States, while the 'Long Scale' is in use in, for example, Europe.

How Many Watts in a Kilowatt

If you wonder how many watts (W) are there in a kilowatt (kW), just check the chart:

1 kW = 1 000 W

This is a strictly mathematical 'issue' and can be even continued:

1 kW = 1 000 W = 1 000 000 mW (milliwatt) = 106 mW = 1 000 000 000 μW (microwatt) = 109 μW

It may look confusing, but multiplying large numbers using SI proxies is very simple:

1 kW = 103 W = 103 * 103 mW = 103+3 mW = 106 mW

Or, just use a good calculator and be careful with typing the decimals.

How Many Kilowatts in a Megawatt

kilowatts to megawatts

Similarly, if you want to know how many kilowatts (kW) are there in a megawatt (MW), just check the chart:

1 MW = 1 000 kW = 103 kW = 103 * 103 W = 103+3 W = 106 W = 1 000 000 W

One kilowatt is a thousand watts, one megawatt is a thousand kilowatts and/or a million watts.

If You want, You can easily express yottawatts using yoctowatts:

1 YW = 1024 W = 1024 * 1024 yW = 1024+24 yW = 1048 yW

Why would anybody in a real-life electrical engineering use such large or small units, I don't know, but it is a good way of showing the actual scale from one end to another of the SI prefixes chart.


Long Story Short: Unit conversions, including W to kW to MW and back, are easy, just be sure to remember right formulas:

1 MW = 1 000 kW = 1 000 000 W

And don't forget to use the calculator, especially for very large or very small values.