What it means
Capital here means the buffer belonging to the bank's owners rather than to its depositors or bondholders: mainly ordinary shares and retained profits, known as Tier 1, plus certain subordinated instruments that count as Tier 2. Customer deposits are not capital, because they are money the bank owes back.
Risk-weighting is the clever part of the calculation. A loan to a highly rated government might be weighted at 0%, a well-secured residential mortgage at 35% and an unsecured business loan at 100%, so $100 million of mortgages counts as only $35 million of risk-weighted assets while the same sum lent unsecured counts in full.
Under the international Basel framework, banks are generally expected to hold total capital of at least 8% of risk-weighted assets, with additional buffers layered on top that push the practical requirement into low double digits. Supervisors also add firm-specific requirements where they believe a bank has understated its own risks.
For anyone outside banking, the ratio matters because it governs how much a bank can lend. A bank sitting close to its minimum must either raise fresh equity, retain profits instead of paying dividends, or shrink its loan book, and that last option is what borrowers experience as a credit squeeze.
The nuance is that the ratio depends entirely on risk weights, which larger banks partly model themselves. Two banks with almost identical loan books can therefore report different ratios, which is why a simpler leverage ratio, capital divided by total unweighted assets, is published alongside it as a cross-check.
In practice
Real-world examples.
Example
A commercial property developer is told his bank has paused new lending in his sector. The relationship manager explains that regulators have raised the risk weight applied to speculative development loans, so each new facility now consumes far more capital than it did a year ago.
Example
A bank's board debates whether to pay a full dividend after a strong year. The finance director models the effect on the capital adequacy ratio and shows it would fall from 13.2% to 12.1%, still above requirements but leaving less room for the loan growth the strategy assumes.
Example
An investor comparing two listed banks notices one reports a 16% ratio and the other 11%. Reading further, she finds the first holds mostly government bonds and prime mortgages while the second lends heavily to small businesses, so the difference reflects business mix as much as caution.
Think of it
“Capital adequacy shows if a bank has enough capital cushion for its risky assets-a safety buffer.
Formula
Calculation
Capital Adequacy Ratio = (Tier 1 Capital + Tier 2 Capital) / Risk-Weighted Assets
Take a mid-sized commercial bank.
Tier 1 capital (ordinary shares plus retained earnings): $900,000,000.
Tier 2 capital (qualifying subordinated debt): $300,000,000.
Total regulatory capital = $900,000,000 + $300,000,000 = $1,200,000,000.
Risk-weighted assets: $12,000,000,000.
Capital Adequacy Ratio = $1,200,000,000 / $12,000,000,000 = 10%.
Tier 1 ratio = $900,000,000 / $12,000,000,000 = 7.5%.
Against an 8% total minimum, the bank needs $960,000,000 of capital, so it holds $240,000,000 more than the floor. Because each dollar of capital supports $12.50 of risk-weighted assets at an 8% requirement, that surplus supports up to $3,000,000,000 of additional risk-weighted lending before the bank hits the minimum. If it wanted to write $3,000,000,000 of unsecured business loans at a 100% weight, it would use the whole cushion; the same money lent as mortgages at a 35% weight would use less than half of it.Case study
Seen in the real world.
Meridian Union Bank is an illustrative, fictional lender created to show how capital adequacy shapes strategy. In this invented example the bank held $1,200,000,000 of total capital against $12,000,000,000 of risk-weighted assets, giving a 10% ratio at a time when its supervisor expected 10.5% including buffers.
Being marginally short left the bank with three choices: raise equity at a share price it considered too low, cancel its dividend, or reduce risk-weighted assets. It chose the third, selling a $900,000,000 portfolio of unsecured small business loans and redeploying part of the proceeds into residential mortgages carrying a 35% weight.
The illustrative outcome was that the reported ratio rose above the requirement within two quarters without a single new share being issued. The cost was strategic rather than financial: Meridian had exited the customer segment that generated its best margins, and its net interest income fell for three consecutive years afterwards.
Watch out
Common mistakes.
- Confusing capital with cash. Capital is a funding structure describing who bears losses, not a pile of money sitting in a vault, and a well-capitalised bank can still fail for lack of liquidity.
- Comparing the ratios of banks in different countries as if they were identical. National regulators apply different buffers and permit different modelling approaches, so headline percentages are not always like for like.
- Assuming a higher ratio is always better for shareholders. Excess capital drags on return on equity, so a bank sitting far above its requirement may simply be using its owners' money inefficiently.
Questions
People also ask.
What is the difference between the capital adequacy ratio and the leverage ratio?
The capital adequacy ratio divides capital by risk-weighted assets, while the leverage ratio divides it by total assets with no weighting at all, acting as a backstop when risk models are too generous.
What counts as Tier 1 versus Tier 2 capital?
Tier 1 is the loss-absorbing core of ordinary shares and retained earnings plus some perpetual instruments, while Tier 2 is a weaker layer, typically dated subordinated debt that only absorbs losses if the bank actually fails.
Why should a non-bank business care about this ratio?
Because it determines your bank's appetite for new lending, and a lender close to its minimum will reprice, shorten or decline facilities regardless of how good your own numbers look.
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