Power Score

[Saxif]

How is this worked out roughly?

I assume it's the base strength of a unit + promotions to get total strength, then add everything together + a little bit more for walls and castles.

Does it add anything for cultural defences? Do higher tech units modify in a biased way? Say a crossbow giving a bigger number than a swordsman?

I went to war recently despite struggling to get a good military advantage on my opponent but in the end started beating him because I had a stack of axe men and he had a mix of sword, axe and archer defending and of those he had fewer axemen. So I assume promoted swordsmen made it look like his military was higher than its actual effectiveness?

 

[2metraninja]

Units numbers and type, certain techs (Gunpowder, etc), walls, castles, barracks, Chichen Itza, population - all this is included.

Usually you should be fine even having half the powergraph of an AI due to superior human thinking. Playing versus human who have twice your power though means almost sure defeat for you

For comprehensive list you can visit this link

 

[Ghpstage]

Promotions don't add anything to your power, nor does cultre defense, and unit power itself isn't a factor. The factors are the type of unit, your population, some buildings, some wonders and some techs

Follow the link 2metraninja posted for the specific soldier values for different things, your power is then the total of your soldier count.