snip
We never get definitive answers about anything in Dragon Ball. It's always in flux and nebulous. Considering this quote,
I suppose if Beerus' strength is a 10, [Super Saiyan] God would be right about 6. Only, Saiyans rapidly increase in strength as they fight against strong opponents, so the longer they fought, the more that gap would shrink, and it might even be possible for them to eventually turn the tables. Incidentally, I guess Whis would be about a 15.
http://www.kanzenshuu.com/translations/battle-gods-animanga-akira-toriyama/
I realize this vision may have been retconned a bit by Super's production, but I have little reason to think it wouldn't loosely hold true.
I'd say Goku's closing in at 7 or, if I'm being very generous, 7.5. Goku sandbags all the time and they've been fighting weird opponents lately, so it's hard to gauge.
And then you have stuff like -- if SSG is a 6, and Kaioken is a flat power multiplier, why wouldn't he be 60 or 120? So the disparity between numbers must be pretty wide and perhaps not linear (consider MMORPG experience requirements for leveling up as an example formula). Goku could easily be hovering at 6.5 territory.