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.

Updated: September 23, 2022.

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

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, and 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 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.

How Many Watts in a Megawatt

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

1 MW = 1 000 kW = 1 000 000 W = 10⁶ W

So, one Megawatt is a million Watts.

How often one uses Megawatts (MW) in real life?

Well, the Rimac Nevera hypercar's maximum power output is 1914 HP which is ~1.4 MW, and that is 1400000 Watts.

And that is a lot.

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

1 MW = 1 000 kW = 1 000 000 W = 1 000 000 000 mW

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