I keep seeing this on my equipment and cannot seem find an explanation that solves this annoying occurrence. Today I received my new USB to SATA external adapter. On the adapter interface, it says it needs 12V 2A. The power supply they sent says 12V 2000mA.

Power supply

SATA adapter

If 2000mA = 2A why do they confuse things by using 2000mA?

  • \$\begingroup\$ Makes no sense yet common. \$\endgroup\$
    – winny
    Commented Apr 23, 2022 at 22:36
  • 3
    \$\begingroup\$ Marketing managers may believe that 2000 mA looks more powerful than 2A. But nobody uses 0.002 kA instead. Believe me, 2000 mA really is 2 A \$\endgroup\$
    – Uwe
    Commented Apr 23, 2022 at 22:37
  • 3
    \$\begingroup\$ 2A is equal to 2000mA and which part of it is confusing? \$\endgroup\$
    – Justme
    Commented Apr 23, 2022 at 22:38
  • 1
    \$\begingroup\$ Suppose it was a 500mA wall wart. That's 0.5A. That tiny little decimal point might be missed by someone with poor eyesight. Or it might be scuffed off. 500mA is less likely to be mistaken. \$\endgroup\$
    – glen_geek
    Commented Apr 23, 2022 at 22:59
  • \$\begingroup\$ it may be required by one of the certification labs \$\endgroup\$
    – jsotola
    Commented Apr 23, 2022 at 23:16

2 Answers 2


"If 2000mA = 2A why do they confuse things by using 2000mA?"

There is no confusion: 2000 mA is unambiguous.

But in engineering, 2000 mA equals 2.000 A, not 2 A.

So a PSU manufacturer would be stating that their PSU can supply up to 2.000 A but not 2.001 A and above.

I doubt here that the PSU manufacturer is using a circuit that goes into current limit that precisely, down to the milliamp.

It's more likely that they express it in mA because that unit format allows for an existing/possible range of products that do go down to lower max. mA. For example, if they want their spec format to support a 100 mA PSU, a 250 mA, a 5 A and so on.

Look on the websites of the larger PSU manufacturers, at the products in a range. You'll see that's why the same units are used to make a range of products easier to differentiate between.

It's not some marketing attempt at making it look more impressive or anything like that.

  • 1
    \$\begingroup\$ That makes sense! Thank you Tony for taking time to explain that.. \$\endgroup\$
    – zdvdla
    Commented Apr 23, 2022 at 22:48

Because the power supply is not made by the same people as the disk adaptor, and their marketing department felt that 2000mA looked better then 2A.

I suspect the safety agencies require the current ratings, but are not too fussed about mA Vs A, and 2000 is biggerer then 2....

I don't think there is any more to it then that, and hell I might have once run a student radio station "10,000 milliwatts of music power", that sort of thing really is just marketing.

  • \$\begingroup\$ Thank you Dan!! \$\endgroup\$
    – zdvdla
    Commented Apr 23, 2022 at 22:46
  • \$\begingroup\$ Sounds just like marketing to use the more sensational number 2000 rather than the simple number 2 \$\endgroup\$
    – zdvdla
    Commented Apr 23, 2022 at 22:49
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    \$\begingroup\$ It might not all be marketing. The vendor might sell a series of similar PSUs, e.g. 800 mA, 1200 mA and 2000 mA. It'd be awkward to use 2 A on the latter. \$\endgroup\$
    – Zac67
    Commented Apr 24, 2022 at 7:34

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