# Understanding credit-score fluctuations [closed]

Recently an old credit account that I've had sitting idle was closed due to inactivity. I get credit-score updates from the issuer (who still maintains the credit account that I actually use), and this event caused a small drop in my score (812 to 805, so -7 points) apparently because my total available credit decreased.

So we've got a drop in total credit from \$25000 to \$11000 (the fact that the bulk of my credit was with the card I never use came as a surprise to me, too), with a corresponding drop of 7 points to the credit score. That looks like (but probably isn't) 0.5 points per \$1000 of available credit. And fair enough, I guess.

The part I'm wondering about is that the card issuer also provides a "simulator" tool that predicts what your credit score will do if you take various actions. I thought I could get my 7 points back by just increasing the limit on the card I still have up to \$25000, but when I put that into the simulator it kicked the score down to an atrocious 780-something. Strangely, if I simulate adding a second card to bring my total credit up to \$25000, instead of a plummeting score the simulator gives 5 of the 7 points back.

I guess the core question is, why does having \$25000 in credit available across two accounts produce a significantly better score than having the same amount of credit in a single account? If someone is trying to max out their reported credit score, what's the optimal configuration of total credit and number of cards/accounts?

• As the details of the credit score algorithm aren't public, any answer is going to be speculation. Commented Apr 16, 2018 at 12:03
• @ChrisInEdmonton But someone must know the details of the algorithm. Someone had to code it. Maybe they'll see the question and remember enough details to answer. Commented Apr 16, 2018 at 12:15
• I have tried such a simulator(from Chase), and it is complete off most of the time. It might be useful for people with poor scores, but if your score is pretty good already, it is just reporting contradicting nonsense to me. Commented Apr 16, 2018 at 12:42
• Simulators are all notoriously inaccurate.
– Norm
Commented Apr 16, 2018 at 12:53
• @aroth Yes, someone coded it but the exact details are proprietary so they can't share it. The best you can do is go by the rough guidelines from each scorer and anecdotal evidence. Commented Apr 16, 2018 at 13:26