What is a credit limit, and what is credit utilisation?
Nobody is impressed that you have a large limit. They are watching how much of it you needed.
Both paid in full. Only one of them looks comfortable.
What utilisation actually measures
It is a ratio: balance divided by limit, expressed as a percentage. Scoring models look at it per card and across all your cards together, and both matter.
The reason it carries so much weight is that it is a live signal rather than a historical one. Your repayment history describes what you did over years. Your utilisation describes how much borrowing capacity you are consuming right now, which is a better predictor of imminent difficulty. Someone using almost all of their available credit is, statistically, closer to trouble than someone using a tenth of it, regardless of how well both have paid in the past.
The conventional guidance is to stay below thirty percent. That number is a rule of thumb rather than a cliff, and lower is generally better, but the difference between ten and twenty-five percent is far smaller than the difference between thirty and eighty.
One thing worth separating, because the coincidence causes real confusion. In the best-known scoring model, the category called amounts owed accounts for around thirty percent of the score, and utilisation is one element inside that category alongside how many accounts carry balances and how much you owe across account types. That thirty percent is not the same thirty percent as the utilisation guidance above. The two numbers are unrelated, and the widely repeated claim that utilisation *is* thirty percent of your score conflates them.
The timing trap
Here is the part that catches people who pay in full every month and still see a mediocre score.
Utilisation is measured from what your issuer reports to the credit bureau, and that report is usually generated on your statement date, not after you pay. So if you spend heavily during the month and clear the balance on the due date, the bureau may still have recorded a high balance, because the snapshot was taken before your payment landed.
You are behaving impeccably and the record shows otherwise. The fix is unglamorous: either pay down part of the balance before the statement date rather than after, or spread spending across cards so no single one reports a high figure.
Why a limit increase can help, and when it does not
Because utilisation is a ratio, raising the denominator lowers it without changing anything you do. A limit increase on an unused card genuinely improves the picture.
Two cautions. A lender may run a hard enquiry to grant the increase, which is a small short-term cost against a longer-term gain. And a larger limit only helps if the spending does not expand to fill it, which it very often does. Closing an unused card has the opposite effect: it removes its limit from the total and pushes the ratio up, which is why closing old cards frequently makes a score worse rather than tidier.
A library card that allows ten books at a time. Borrow nine every visit and return them all promptly, and you are a perfect member who always seems to be at the edge. Borrow two from a card that allows fifty, and you look like someone with room to spare. Same reading, same returns, very different impression.
Where you meet it
Every score that dropped in a month you did nothing wrong. Every unsolicited limit increase offer. Every piece of advice to close old cards, which is usually the opposite of what helps.