Arduino analog to digital conversion - resolution 1/1023 or 1/1024?

Hi folks. The link below portions out the 5V into pieces of 5/1023.

https://learn.sparkfun.com/tutorials/analog-to-digital-conversion

"The ADC reports a ratiometric value. This means that the ADC assumes 5V is 1023 and anything less than 5V will be a ratio between 5V and 1023."

Does arduino really portion it out to 1023 parts? Or does it actually portion 5V by dividing 5V by 1024 to get 5/1024 as the smallest 'piece', and the highest voltage becomes (5 - 5/1024) ?

Just trying to establish whether the voltage increment is actually 5/1024 volt, or 5/1023 volt. This isn't a case of 'does it matter?'. It's a case of ... "what's the actual case?". Thanks all!

This topic has been discussed many many times on this forum. Do a search for "1023 or 1024" for lots of reading.

groundFungus:
This topic has been discussed many many times on this forum. Do a search for "1023 or 1024" for lots of reading.

Cool! Thanks G.F.

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UPDATE: Ok..... back again. Looks like the general consensus is divide by 1024, not divide by 1023. So the voltage range covered is 0 V up to (5 - 5/1024) V. Level 1 is 0*(5/1024) = 0V........level 1024 is 1023*(5/1024) V. So '5V' itself is not covered .... but the next value below 5V which is relatively close to "5V" ..... is covered. Thanks again.

I go with the solution of the hard drive manufacturers and round it down to 1000. Then I get a nice little boost in my voltage readings.