Risk-weighted assets (RWA) are a bank's total assets weighted by their regulatory credit risk category under Basel III. RWA drives the amount of capital a bank must hold — higher-risk SMB loans get higher RWA weights, consume more bank capital, and are therefore priced higher than lower-risk assets like Treasury securities.
Not all bank assets carry the same risk. US Treasury securities have near-zero default probability. A residential mortgage is lower risk than a commercial loan. An unsecured SMB loan is higher risk than an SBA-guaranteed loan. Basel III's risk-weighting framework assigns each asset type a risk weight (0% to 150%+) that determines how much regulatory capital the bank must set aside. Common risk weights under the standardized Basel III approach: US Treasuries = 0% RWA (no capital required). Residential mortgages = 50–100% RWA depending on LTV. SBA-guaranteed portion of loans = 0% RWA (federal government guarantee = risk-free for regulatory purposes). Unguaranteed commercial loans to SMBs = 100% RWA (standard). Highly leveraged transactions = 150%+ RWA. Consumer credit cards = 75–100% RWA. The regulatory minimum capital requirement is: Tier 1 capital ≥ 6% of RWA. A bank with $1B in commercial SMB loans (all at 100% RWA = $1B RWA) must hold at least $60M in Tier 1 capital against those loans. The same bank lending $1B to the federal government (0% RWA = $0 RWA) needs $0 capital. This asymmetry directly impacts the pricing and availability of SMB credit. For borrowers, understanding RWA explains: (1) why SBA-guaranteed loans often have lower rates than equivalent unguaranteed commercial loans (SBA guarantee = 0% RWA = less capital consumed); (2) why bank credit standards vary across loan types; (3) why commercial real estate lending tightens during bank capital stress (banks de-risk by reducing high-RWA assets). Source: FDIC Basel III information at https://www.fdic.gov/regulations/applications/assessmentguide/.
One key reason: the SBA-guaranteed portion of an SBA loan carries 0% RWA under Basel III (backed by the US federal government). A conventional commercial loan of the same amount carries 100% RWA. The RWA difference means the bank must hold significantly more capital against the conventional loan, increasing the bank's effective cost of making it. This capital efficiency advantage partially offsets the SBA guarantee fee and allows SBA loans to be priced competitively or below equivalent conventional loans.
Total assets is the sum of all bank assets at book value. RWA is total assets after multiplying each asset by its risk weight. A bank with $10B in total assets but 50% concentrated in Treasuries (0% RWA) and 50% in mortgages (50% RWA) has $10B total assets but only $2.5B RWA. Capital requirements are calculated on RWA, not total assets — giving banks incentive to hold lower-RWA assets.
Unguaranteed SMB loans receive 100% (or higher) RWA treatment under Basel III, making them capital-intensive for banks. During periods of bank capital stress, banks reduce high-RWA assets first — often including SMB and commercial lending. This is a structural reason why SMB credit access is more cyclical and volatile than, for example, mortgage credit. Government guarantee programs (SBA) reduce RWA to 0% on the guaranteed portion, directly improving capital efficiency and credit availability.