The capital adequacy ratio measures how much qualifying capital a bank holds against its risk-weighted assets, expressed as a percentage. Under federal regulation, every national bank and federal savings association must satisfy four separate minimums at all times: a Common Equity Tier 1 ratio of 4.5 percent, a Tier 1 capital ratio of 6 percent, a total capital ratio of 8 percent, and a leverage ratio of 4 percent. The first three use risk-weighted assets in the denominator; the leverage ratio uses total on-balance-sheet assets and serves as a backstop.1eCFR. 12 CFR 3.10 – Minimum Capital Requirements
What Counts as Capital
The numerator in a capital adequacy ratio is not just any money the bank has. Regulators sort capital into tiers based on how reliably each type absorbs losses while the bank is still operating.
Tier 1 Capital
Tier 1 is the strongest layer. Its main component is Common Equity Tier 1, or CET1: common stock and retained earnings. This is permanent money, with no maturity date and no guaranteed dividend, so it takes losses first. Additional Tier 1 instruments, such as non-cumulative perpetual preferred stock, sit just below CET1. They rank ahead of common stock for dividends but remain perpetual and can absorb losses while the bank continues to operate.
Tier 2 Capital
Tier 2 is supplementary. It includes subordinated debt and certain loan loss reserves. These instruments can absorb losses in a failure, but maturity dates and other features make them less immediately available in a going-concern crisis. Regulation caps how much Tier 2 can count toward requirements, keeping the bulk of the cushion in Tier 1.
The Four Minimum Ratios
Every national bank and federal savings association has to clear all four of these simultaneously. Falling below any one triggers regulatory consequences.
- Common Equity Tier 1 ratio: 4.5 percent of risk-weighted assets
- Tier 1 capital ratio: 6 percent of risk-weighted assets
- Total capital ratio: 8 percent of risk-weighted assets
- Leverage ratio: 4 percent of total on-balance-sheet assets (not risk-weighted)
The leverage ratio matters because it ignores risk weights entirely. Even if a bank’s risk-weighted assets look small, it still has to hold capital equal to at least 4 percent of everything on its balance sheet.1eCFR. 12 CFR 3.10 – Minimum Capital Requirements These minimums are floored in statute: 12 U.S.C. § 5371, the Collins Amendment enacted through Dodd-Frank, prevents federal banking agencies from dropping requirements below the levels that applied to insured depository institutions as of July 2010.2Office of the Law Revision Counsel. 12 USC 5371 – Leverage and Risk-Based Capital Requirements
How to Calculate the Capital Adequacy Ratio
The formula is qualifying capital divided by risk-weighted assets. The arithmetic is easy. The work is in the denominator.
Risk Weights
Risk-weighted assets adjust each holding’s dollar value by how likely it is to generate a loss. Federal regulation assigns weights to broad categories:
- Zero percent: cash held in the bank’s vaults and exposures to the U.S. government or its agencies.
- 50 percent: first-lien residential mortgages on owner-occupied or rented property, provided the loan was made under sound underwriting standards and is not significantly past due.
- 100 percent: corporate loans and most other commercial exposures.
A bank holding $50 million in Treasuries and $50 million in commercial loans does not have $100 million in risk-weighted assets. The Treasuries contribute zero and the commercial loans contribute $50 million, so risk-weighted assets total $50 million.3eCFR. 12 CFR 3.32 – General Risk Weights
A Worked Example
Take a bank with $10 million in CET1, $2 million in Additional Tier 1, and $3 million in Tier 2. Tier 1 capital is $12 million; total capital is $15 million. On the asset side, the bank holds $80 million in commercial loans (100 percent weight), $40 million in qualifying residential mortgages (50 percent weight), and $30 million in Treasury securities (zero weight). Risk-weighted assets work out to:
($80M × 1.0) + ($40M × 0.5) + ($30M × 0.0) = $100 million
Each ratio then follows:
- CET1 ratio: $10M ÷ $100M = 10 percent (minimum 4.5 percent)
- Tier 1 ratio: $12M ÷ $100M = 12 percent (minimum 6 percent)
- Total capital ratio: $15M ÷ $100M = 15 percent (minimum 8 percent)
- Leverage ratio: $12M ÷ $150M total assets = 8 percent (minimum 4 percent)
The bank clears every threshold. Portfolio composition matters as much as capital levels. If the same bank swapped its Treasuries for commercial loans, risk-weighted assets would jump to $130 million and every risk-based ratio would drop, even though actual capital didn’t change by a dollar.
Buffers on Top of the Minimums
Meeting the minimums keeps a bank out of undercapitalized status, but the bar to operate without restrictions is higher. Several buffers sit above the four minimums.
Capital Conservation Buffer
Every bank must maintain a 2.5 percent capital conservation buffer above its minimum CET1 requirement. Effectively, that means CET1 of at least 7 percent to avoid restrictions on dividends and discretionary bonus payments. A bank operating inside the buffer zone is not technically undercapitalized, but the deeper it drops into that zone, the more of its earnings it must retain rather than distribute.4eCFR. 12 CFR 217.11 – Capital Conservation Buffer, Countercyclical Capital Buffer Amount, and GSIB Surcharge
Countercyclical Capital Buffer
Regulators can activate a countercyclical buffer of up to 2.5 percent during periods of excessive credit growth. In the United States, this buffer has remained at zero since its introduction, but the authority to raise it is on the books.
G-SIB Surcharge
The largest and most interconnected banks face an added surcharge. Globally, 29 institutions are currently designated as Global Systemically Important Banks.5Financial Stability Board. 2025 List of Global Systemically Important Banks (G-SIBs) The surcharge starts at 1.0 percent of risk-weighted assets and rises based on a scoring methodology that weighs size, interconnectedness, cross-border activity, and complexity.6Federal Register. Regulatory Capital Rule (Regulation Q) – Risk-Based Capital Surcharges for Global Systemically Important Bank Holding Companies
Supplementary Leverage Ratio
Large banking organizations also have to maintain a supplementary leverage ratio of at least 3 percent. Unlike the standard leverage ratio, this one includes off-balance-sheet exposures like derivatives and unfunded commitments in the denominator. G-SIBs face an enhanced version with an additional leverage buffer on top of the 3 percent floor.7Federal Register. Regulatory Capital Rule – Modifications to the Enhanced Supplementary Leverage Ratio Standards
What Happens When a Bank Falls Short
Under 12 U.S.C. § 1831o, regulators sort every insured depository institution into one of five capital categories, with escalating consequences at each step. The framework is called Prompt Corrective Action, and it exists to force intervention before a struggling bank slides past the point of recovery.
The Five Categories
- Well-capitalized: total capital ratio of 10 percent or more, Tier 1 of 8 percent or more, CET1 of 6.5 percent or more, and leverage ratio of 5 percent or more, with no directive to meet a specific capital level.
- Adequately capitalized: meets the four minimums but not the well-capitalized thresholds.
- Undercapitalized: falls below any one of the adequately capitalized thresholds.
- Significantly undercapitalized: falls significantly below the required minimums on any capital measure.
- Critically undercapitalized: tangible equity of 2 percent of total assets or below.
The step from adequately capitalized to well-capitalized carries real weight. A bank that only meets the minimums faces limits a well-capitalized bank does not, including restrictions on accepting brokered deposits.8eCFR. 12 CFR 6.4 – Capital Measures and Capital Category Definitions
Restrictions at Each Level
Once a bank crosses into undercapitalized territory, restrictions apply automatically. The bank must file a capital restoration plan within 45 days, and asset growth freezes unless the plan has been accepted. Acquisitions, new branches, and new business lines all require prior regulatory approval.9Office of the Law Revision Counsel. 12 USC 1831o – Prompt Corrective Action
Significantly undercapitalized banks face stronger measures. Regulators can require the bank to sell shares to raise capital, cap the interest rates it offers on deposits, order the removal of directors or senior officers, prohibit executive bonuses, and even require a parent company to divest the bank. The statute presumes several of these will be imposed unless regulators specifically find that a given action wouldn’t help.
Critically undercapitalized institutions face the endgame. Within 90 days, the appropriate federal agency must appoint a receiver or conservator, unless it documents why an alternative would better protect the deposit insurance fund. Separately, statute prohibits a bank from paying any dividend that would drop it into undercapitalized status, and the conservation buffer rules impose graduated payout restrictions well before that point.10Federal Deposit Insurance Corporation. Financial Institution Letter – Requests from S-Corporation Banks for Dividend Exceptions to the Capital Conservation Buffer
A Simpler Path for Community Banks
Not every bank has to work through the four-ratio framework. Regulators created the Community Bank Leverage Ratio to give smaller institutions a simpler option that replaces all four risk-based ratios with a single leverage measure.
A bank can opt in if it has less than $10 billion in total consolidated assets, maintains a leverage ratio above 8 percent, and meets criteria on off-balance-sheet exposures and trading activity. A qualifying bank that stays above the CBLR threshold is treated as well-capitalized for all regulatory purposes without calculating risk-weighted assets at all.11Office of the Comptroller of the Currency. Community Bank Leverage Ratio – Final Rule
A bank that slips below the qualifying criteria but stays above a 7 percent leverage ratio gets a grace period of up to four consecutive quarters to come back into compliance, subject to a limit of eight quarters in any rolling five-year window. Falling to 7 percent or below ends the grace period and pulls the bank back into the full risk-based framework immediately.12Federal Register. Regulatory Capital Rule – Community Bank Leverage Ratio Framework