@Anonymous wrote:Short answer:
Not all cards, just one.
Long-term strategy:
You have a lot of freedom here. As long as you pay your balances in full each month, and stay away from maxing out any particular card, you are fine. This is because the "Amounts Owed" category is just a snapshot in time with no "memory." Even if every card reported a balance one month, and furthermore even if the overall utilization were high that same month, that "hit" to your score would vanish once your accounts started showing mostly zeros (see below).
Optimal strategy (only needed in rare stuations):
This is something you do shortly before you need as high a score as you can possibly get: e.g. before buying a car, or a mortgage pre-approval, or if you are trying one month to measure how high you can get your score. The key here is that most of the time you don't need to do this. The general wisdom at myFICO seems to be: render all your reported balances as zero except one card, and for that one card keep the balance positive but < 9% of the card's credit limit. If you are dead set on wringing every conceivable fraction of a point available, you might also keep the raw dollar amount on that card moderate to low as well. (Maybe $100 or so?) That's because FICO also looks at the dollar amount, not just the % utilization.
Source? 
@Anonymous wrote:Thanks. Why 9%? I thought it was 30%? Is 9% the standard for optimal credit utilization?
It was found through testing; 30% doesn't suck but it's not optimal for FICO scoring anecdotally. Most of that testing was done on FICO 04 (Equifax Scorewatch back in the day) and may not entirely hold true on the FICO 8 models but it's a good estimate all things considering. Someday when I'm not trying to stay ultra clean prepping for a mortgage application, I'll probably play some games with my $1K freedom as my only reported balance to see what's what under FICO 8, but it does depend on the individual report.
@Anonymous wrote:Hi Revelate. Are you asking for a source about the claim that FICO looks at the actual amount owed (as opposed to only looking at the amount owed relative to the credit limit)?
Or are you asking for why I tentatively suggested somewhere in the universe of $100? The latter is just a guess. There are documented cases of perfect 850s where the amount is in the couple hundreds.
Hey CGinDixie: the claim that FICO looks at actual amount owed rather than a percentage. Anecdotally at least people's reports do flucutate with balances in the <10% range, I know mine do but I haven't done enough testing under FICO 8 to really pinpoint what my optimum reporting balance is.
I wouldn't read anything into the FICO literature you linked, it is deliberately vague and that wording has been pored over by FICO's non-trivial legal and product (consumer and business) staff.
There was a lot of testing done and percentages held; dollar values come into play at the very low end where some lenders may round to zero (awkward but heard reports of it) and on the high end on determining whether various LOC's are installment or the usual revolving tradeline. Might be some more recent information I haven't seen (been pretty much gone for the last several months) but I'd be fairly surprised with how the algorithm is setup as I don't see the rational implementation measure. $200 used of a $200 aggregate CL is not the same as $200 on $30K aggregate CL, and anecdotally that's held true for everyone we've seen here.
ETA: making an assumption off an 850's individual profile doesn't work, files are unique as people have found different percentages for their optimum scores and with FICO 8 you can have some blemishes and still be at 850, that was clearly demonstrated by android01 and others here on this forum. As such suggesting that someone's 850 is equivalent to the 11th commandment when it comes to balance reporting is a little suspect in my estimation.