Regulatory Capital Requirements: Ratios, Buffers, and Shortfalls

U.S. banks must meet four minimum capital ratios at all times: a Common Equity Tier 1 (CET1) ratio of 4.5 percent, a Tier 1 ratio of 6 percent, a total capital ratio of 8 percent, and a leverage ratio of 4 percent.¹ The first three are measured against risk-weighted assets; the fourth is measured against average total assets without any risk adjustment. These are the floors. On top of them sit buffers that push the effective bank regulatory capital requirements considerably higher for most institutions, and the largest banks face additional surcharges that can bring practical CET1 requirements above 12 percent of risk-weighted assets.

The Four Minimum Ratios

Every regulated bank must clear all four floors simultaneously. Missing any single one triggers supervisory consequences.

CET1 ratio of 4.5 percent — Common Equity Tier 1 capital divided by risk-weighted assets. Only the most loss-absorbent capital counts here.
Tier 1 ratio of 6 percent — CET1 plus Additional Tier 1 capital, divided by risk-weighted assets.
Total capital ratio of 8 percent — all three tiers combined, divided by risk-weighted assets.
Leverage ratio of 4 percent — Tier 1 capital divided by average total consolidated assets, ignoring risk weights entirely.

The leverage ratio is a backstop. Without it, a bank could load up on assets that carry very low risk weights, making the risk-based ratios look strong while the balance sheet grew heavily leveraged. Treating every dollar of assets the same catches that.

Large banks subject to Category I through III standards face an additional supplementary leverage ratio (SLR) of at least 3 percent, calculated against a broader base that includes certain off-balance-sheet exposures. Global systemically important banks must hold a further 2 percent leverage buffer above the 3 percent floor to avoid restrictions on dividends and bonuses.²

What Counts as Capital

Regulators sort qualifying capital into tiers based on how reliably each type absorbs losses. Only the strongest forms count toward the strictest ratios.

Common Equity Tier 1

CET1 is the highest-quality capital a bank holds. It includes common stock, retained earnings, accumulated other comprehensive income, and qualifying minority interests.³ These resources absorb losses while the bank is still open for business. Because CET1 is permanent and carries no obligation to make fixed payments, regulators treat it as the most dependable line of defense.

Some assets that look like capital on paper are stripped out before the ratio is calculated. Goodwill, most intangible assets, and deferred tax assets arising from net operating loss carryforwards are all deducted because they cannot reliably be converted to cash during a crisis.⁴ A bank that made a large acquisition and carries significant goodwill will see its usable CET1 reduced accordingly.

Additional Tier 1 Capital

Additional Tier 1 (AT1) also absorbs losses while the bank keeps operating, but the instruments qualifying here sit a step below common equity.³ The most common AT1 instruments are noncumulative perpetual preferred stock and contingent convertible bonds, securities that can be written down or converted to common equity if capital falls below a trigger point. Traditional subordinated debt does not qualify; the instruments must be perpetual with no maturity date and carry no obligation to pay dividends.

Tier 2 Capital

Tier 2 only comes into play when a bank is failing. It absorbs losses after CET1 and AT1 are exhausted, so depositors and general creditors are protected before these instruments take a hit.³ Tier 2 includes subordinated debt with an original maturity of at least five years and certain loan-loss provisions. Because these instruments are less permanent, regulators count them only toward the total capital ratio, not the more stringent CET1 or Tier 1 measures.

Risk-Weighted Assets: The Denominator

A bank’s capital ratios are meaningful only relative to the risks it has taken on. The denominator of each risk-based ratio is not total assets but risk-weighted assets (RWAs), which adjust every balance-sheet item by a percentage reflecting how likely it is to produce a loss.

On-Balance-Sheet Weights

Cash and direct obligations of the U.S. government carry a zero percent risk weight. A dollar of Treasury securities adds nothing to a bank’s RWA total.⁵ Residential mortgages receive weights that scale with loan-to-value, ranging from 20 percent at 50 percent LTV or below up to 70 percent for loans exceeding 100 percent LTV.⁶ Most unsecured corporate loans receive a 100 percent weight, meaning every dollar counts fully against capital requirements.

The math is straightforward. A $10 million commercial loan at 100 percent contributes $10 million to RWAs. A $10 million pool of low-LTV residential mortgages at 50 percent contributes $2 million. A bank holding mostly Treasuries and low-LTV mortgages needs far less capital than one making aggressive commercial loans, which is the incentive regulators intend.

Off-Balance-Sheet Exposures

Commitments a bank has made but not yet funded — letters of credit, guarantees, undrawn loan commitments — also generate risk-weighted assets. The bank first converts them to a credit-equivalent amount using a credit conversion factor (CCF), then applies the appropriate risk weight.⁷

A 100 percent CCF applies to financial standby letters of credit, guarantees, and repurchase agreements. The full amount is treated as if already on the books.
A 50 percent CCF applies to performance bonds, bid bonds, and loan commitments over one year that the bank cannot unconditionally cancel.
A 20 percent CCF applies to trade-related contingencies and short-term commitments of one year or less that the bank cannot unconditionally cancel.
A 0 percent CCF applies to unused commitments the bank can cancel at any time without conditions.

Operational risk and market risk exposures add to the RWA total as well, capturing possible losses from internal failures, fraud, or adverse price movements in trading positions. The sum of all these components becomes the denominator in each capital ratio calculation.

Buffers Stacked on the Minimums

The 4.5, 6, and 8 percent floors are only the starting point. Several buffers stack on top, and breaching any of them restricts a bank’s ability to pay dividends, buy back stock, or pay discretionary bonuses.

Capital Conservation Buffer and Stress Capital Buffer

Most banks must maintain a capital conservation buffer of 2.5 percent of CET1 above the 4.5 percent minimum.⁸ For large banks subject to Federal Reserve stress testing, that static 2.5 percent floor is replaced by a firm-specific stress capital buffer (SCB). The SCB equals the decline in a bank’s CET1 ratio under a severely adverse stress scenario plus planned dividends over the stress horizon, with a floor of 2.5 percent.⁹ A bank whose balance sheet would deteriorate sharply in a recession gets a higher SCB, forcing it to hold more capital in good times.

When a bank’s buffer falls below the required level, distribution restrictions kick in on a quartile scale. A bank in the top quartile of its buffer can distribute up to 60 percent of eligible retained income, dropping to 40 percent, then 20 percent, then zero as the buffer erodes further.8 These restrictions hit before the bank breaches the minimum ratios themselves, giving it time to rebuild capital.

Countercyclical Capital Buffer

The Federal Reserve can activate a countercyclical capital buffer (CCyB) of up to 2.5 percent when systemic vulnerabilities run meaningfully above normal.¹⁰ The Board reviews the appropriate level at least annually, weighing asset valuations, leverage in the financial and nonfinancial sectors, and liquidity conditions. The CCyB has remained at zero percent since the framework was introduced, though regulators can raise it at any time.

G-SIB Surcharge

The largest and most interconnected banks face an extra layer of capital called the G-SIB surcharge. A bank’s systemic importance is scored across five categories: size, interconnectedness, cross-jurisdictional activity, substitutability, and complexity.¹¹ The surcharge equals the higher of two methods, with Method 1 based on the five-category score and Method 2 adding a short-term wholesale funding indicator. Surcharges currently run from 1.0 percent to 4.5 percent or more under Method 1, and Method 2 can produce even higher results for firms heavily reliant on short-term funding.¹²

For the very largest U.S. bank holding companies, the practical CET1 requirement stacks up quickly: 4.5 percent minimum, plus a stress capital buffer (often well above 2.5 percent), plus a G-SIB surcharge, plus any activated CCyB. Effective requirements above 12 or 13 percent of risk-weighted assets are common at the top of the industry.

The Community Bank Alternative

Smaller institutions can skip the risk-based framework entirely. Banks with less than $10 billion in total consolidated assets can opt into the Community Bank Leverage Ratio (CBLR), which replaces all risk-based calculations with a single leverage ratio. A final rule effective July 1, 2026, lowered the CBLR requirement from 9 percent to 8 percent.¹³ A qualifying bank that maintains at least 8 percent Tier 1 capital relative to average total consolidated assets is considered well capitalized and does not calculate risk-weighted asset ratios at all. The same rule extended the grace period for banks that temporarily fall below the threshold from two quarters to four.

What Happens When a Bank Falls Short

Regulators do not wait for insolvency. The Prompt Corrective Action (PCA) framework under 12 U.S.C. § 1831o sorts every insured institution into one of five categories with escalating consequences.¹⁴

Well capitalized: CET1 at or above 6.5 percent, Tier 1 at or above 8 percent, total capital at or above 10 percent, and leverage at or above 5 percent. No restrictions apply.
Adequately capitalized: meets the bare minimums (CET1 4.5 percent, Tier 1 6 percent, total 8 percent, leverage 4 percent) but falls short of the well-capitalized thresholds. The bank cannot accept brokered deposits without a waiver.
Undercapitalized: falls below any one of the minimum ratios. The bank must submit a capital restoration plan and faces restrictions on asset growth and new business activities.
Significantly undercapitalized: CET1 below 3 percent, Tier 1 below 4 percent, total capital below 6 percent, or leverage below 3 percent. Regulators can restrict executive compensation, force sales of shares, and limit interaffiliate transactions.
Critically undercapitalized: tangible equity falls to 2 percent or less of total assets. The agency must appoint a receiver or conservator within 90 days unless it documents that another action would better serve the statute’s purpose.

These thresholds come from the OCC’s PCA regulations, and the Federal Reserve and FDIC apply equivalent standards to the institutions they supervise.¹⁵ The practical takeaway for anyone reading a bank’s capital ratios: the label “well capitalized” means more than clearing the statutory minimums. The gap between adequately and well capitalized is where the first restrictions bite, and every buffer described above sits on top of the well-capitalized thresholds, not the bare floors.p>

1
eCFR. 12 CFR 217.10 – Minimum Capital Requirements
2
Federal Register. Modifications to the Enhanced Supplementary Leverage Ratio Standards
3
Bank for International Settlements. Definition of Capital in Basel III – Executive Summary
4
eCFR. 12 CFR 1240.22 – Regulatory Capital Adjustments and Deductions
5
Federal Deposit Insurance Corporation. Regulatory Capital Rules: Risk-Based Capital Requirements
6
Bank for International Settlements. Basel Framework – CRE20 – Standardised Approach: Individual Exposures
7
eCFR. 12 CFR 217.33 – Off-Balance Sheet Exposures
8
eCFR. 12 CFR 217.11 – Capital Conservation Buffer, Countercyclical Capital Buffer Amount, and GSIB Surcharge
9
eCFR. 12 CFR 238.170 – Capital Planning and Stress Capital Buffer Requirement>
10
Legal Information Institute. 12 CFR Appendix A to Part 217 – The Federal Reserve Board’s Framework for Implementing the Countercyclical Capital Buffer
11
Federal Register. Regulation Q – Risk-Based Capital Surcharges for Global Systemically Important Bank Holding Companies
12
eCFR. 12 CFR 217.403 – GSIB Surcharge
13
Federal Register. Regulatory Capital Rule: Community Bank Leverage Ratio Framework
14
Office of the Law Revision Counsel. 12 USC 1831o – Prompt Corrective Action
15
eCFR. 12 CFR Part 6 – Prompt Corrective Action