The formula
How to calculate credit utilisation
Credit utilisation is the share of your available revolving credit you are using. It is one of the largest single factors in a credit score, and unlike payment history it can be changed within a single billing cycle.
Only revolving credit counts — credit cards, store cards, overdrafts. Mortgages and personal loans are instalment debt and sit outside the calculation entirely.
What to enter:
- Total balances
- Total credit limits
Results appear immediately — there is nothing to submit. Changing a field rewrites the link, so you can share the exact scenario you are looking at.
The order the fields are filled in makes no difference to the result — the calculator recomputes the whole formula from whatever is currently in every field, not step by step. That means it is safe to adjust one number, watch the result change, and adjust it back, without worrying about resetting anything first.
Why credit utilisation matters
A calculation like this usually gets used at a decision point rather than out of curiosity — comparing two real options, checking a number a lender or adviser has quoted, or working out whether a plan that sounded fine in conversation still holds up once it is written down with actual figures. The maths itself is rarely complicated; what is hard is remembering which figures to use and in what order, which is exactly what a dedicated calculator is for.
Beyond a one-off check, the same calculation is worth revisiting whenever the underlying numbers change — a new interest rate, a change in income, a different term. Because the figures live in the page's own web address, coming back to update just one field and compare the new result against the old one takes seconds rather than starting again from a blank page.
It is also worth being clear about what a single figure like this can and cannot settle on its own. It answers the specific question the formula was built to answer, and nothing more — a favourable credit utilisation result does not automatically mean a decision is a good one overall, since plenty of other factors that a formula cannot capture, from personal circumstances to how comfortable a commitment feels, usually matter just as much as the arithmetic. Use the number as one solid input among several rather than the whole of the decision.
In practice, most people arrive at a page like this one having already tried a version of the calculation by hand or in a spreadsheet, and use the calculator here to confirm it rather than replace it. That is a reasonable way to use it — the two should agree to the last decimal place if the same inputs and the same formula are used, and if they do not, the formula shown above is the one to check your own working against first.
Worked example
A concrete run-through, using the values already in the fields:
- Total balances: 3,400
- Total credit limits: 9,000
That gives:
- Credit utilisation: 37.78 %
- Repay this to reach 30%: 700
- Repay this to reach 10%: 2,500
These figures are only the calculator's own starting values, included so the working is visible rather than hidden inside the tool above. Replace them with your own numbers and the same arithmetic applies — nothing about the method changes, only the inputs feeding it.
Reading the result
Below 30% is the widely quoted threshold, and below 10% is where the strongest scores sit. A single card near its limit can hurt even when the overall figure looks fine, because per-card utilisation is assessed too.
Where this goes wrong. Closing an unused card. It removes the limit from the denominator, so utilisation jumps overnight without you borrowing a penny more.
A useful check on any unfamiliar result is to compare it against a rough mental estimate first — round the inputs to convenient numbers and see whether the calculator's answer lands in roughly the same territory. A wildly different figure usually means one of the fields was entered in the wrong unit, most often a percentage typed as a whole number where a decimal was expected, or the reverse.
On the statement date, not the payment due date. Paying in full each month still shows a high utilisation if the statement is generated while the balance is large — paying before the statement date is what moves the reported figure.
No. Scoring models like to see credit being used and repaid. A small reported balance, somewhere in the low single digits as a percentage, typically scores better than nothing at all.
The headline figure is credit utilisation. With 3,400 total balances and 9,000 total credit limits, that comes to 37.78 %. Change any field and the figure moves with it.
Whenever one of the underlying figures changes — a new interest rate, a different balance, an updated term — since the result only reflects what is currently in the fields. There is no need to keep a separate record of past results; the web address for a filled-in version already carries the figures used to produce it.
Not unless a tax rate or a fee is explicitly one of the inputs above. Where it is not, the figure shown is a gross calculation, and any tax due depends on your personal circumstances and current tax rules, which are worth checking separately.
The arithmetic itself is exact — the calculator applies the formula shown above precisely, with no rounding until the final figure is displayed. The uncertainty, where it exists, is entirely in the inputs: an estimated rate or an approximate balance carries that same approximation through to the result.