Exhibit 12 Statement of computation of ratios. 238 Statements re: Computation of Ratios Item 1(l) Business - Statistical Disclosure VI. Return on Equity and Assets Brenton Banks, Inc. (Dollars in thousands) December 31, 1999 1998 1997 Return on average total assets: Net income (before deduction of minority interest) $ 17,204 21,071 18,753 * divided by * Average assets $ 1,943,826 1,780,120 1,649,469 Ratio 0.89% 1.18% 1.14% Return on average common stockholders' equity: Net income $ 16,560 20,351 18,010 * divided by * Average common stockholders' equity $ 134,136 132,422 124,491 Ratio 12.35% 15.37% 14.47% Return on average common stockholders' equity excluding unrealized gains (losses) on assets available for sale: Net income $ 16,560 20,351 18,010 * divided by * Average common stockholders' equity excluding unrealized gains (losses) on assets available for sale 134,569 129,055 122,685 Ratio 12.31% 15.77% 14.68% Common dividend payout ratio: Cash dividends per share $ 0.346 0.317 0.225 * divided by * Net income per share-diluted $ 0.80 0.96 0.83 Ratio 43.25% 33.02% 27.11% 239 Statements re: Computation of Ratios Item 1(l) Business - Statistical Disclosure VI. Return on Equity and Assets Brenton Banks, Inc. (Dollars in thousands) December 31, 1999 1998 1997 Average equity to average assets: Average equity $ 134,136 132,422 124,491 * divided by * Average assets $ 1,943,826 1,780,120 1,649,469 Ratio 6.90% 7.44% 7.55% Equity to assets ratio: Common stockholders' equity excluding unrealized gains (losses) on assets available for sale $ 137,568 131,891 126,159 * divided by * Total assets excluding unrealized gains (losses) on assets available for sale $ 1,991,090 1,936,238 1,715,264 Ratio 6.91% 6.81% 7.36% Tier 1 leverage capital ratio: Common stockholders' equity excluding unrealized gains (losses) on assets available for sale $ 137,568 131,891 126,159 Minority interest 4,608 4,913 4,859 Less: intangibles (6,984) (1,970) (2,087) Less: minimum MSR's to be Deducted 0 (388) --- Tier 1 capital $ 135,192 134,446 128,931 * divided by * Quarterly average total assets excluding unrealized gains (losses) on assets available for sale 1,994,057 1,878,074 1,692,176 Less: intangibles (6,984) (1,970) (2,087) Less: minimum MRS's to be Deducted 0 (388) --- Tier 1 assets $ 1,987,073 1,875,716 1,690,089 Ratio 6.80% 7.17% 7.63% 240 Statements re: Computation of Ratios Item 1(l) Business - Statistical Disclosure VI. Return on Equity and Assets Brenton Banks, Inc. (Dollars in thousands) December 31, 1999 1998 1997 Net Noninterest Margin: Noninterest income $ 29,794 33,358 27,506 Less: Securities gains (losses) 216 665 494 Less: Noninterest expense 65,374 61,392 57,699 Net noninterest income $ (35,796) (28,699) (30,687) * divided by * Year-to-date average assets $ 1,943,826 1,780,120 1,649,469 Ratio -1.84% -1.61% -1.86% Efficiency Ratio: Noninterest expense $ 65,374 61,392 57,699 * divided by * Noninterest income 29,794 33,358 27,506 Less: Securities gains (losses) 216 665 494 Less: Loan gains (losses) 7 81 78 T.E. net interest income 66,575 65,279 63,701 Subtotal 96,146 97,891 90,635 Ratio 67.99% 62.71% 63.66% 241