Originally Posted by
WilcoRoger
Do you have a link to this? I was hit by a 40€ surcharge BUD-HEL for one bag being over 23kg, but could've used this rule to avoid it.
(I still came out winning, as I could cheat the scales for two other bags, both well over 30kg

)
There is no source for this except their online calculator. In case of dispute you can refer them to Finnair's online calculator, or even better, have such printout from their calculator with you.