EXHIBIT 12 KERR-McGEE CORPORATION AND SUBSIDIARY COMPANIES COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES (Millions of dollars) 2003 2002 2001 2000 1999 - --------------------- ---- ----- ---- ------ ---- Income (loss) from continuing operations $254 $(611) $476 $ 817 $138 Add - Provision (benefit) for income taxes 189 (46) 276 437 105 Interest expense 251 275 195 208 191 Rental expense representative of interest factor 22 20 13 11 12 ---- ----- ---- ------ ---- Earnings (loss) $716 $(362) $960 $1,473 $446 ==== ===== ==== ====== ==== Fixed Charges - Interest expense $251 $ 275 $195 $ 208 $191 Rental expense representative of interest factor 22 20 13 11 12 Interest capitalized 10 8 31 5 8 ---- ----- ---- ------ ---- Total fixed charges $283 $ 303 $239 $ 224 $211 ==== ===== ==== ====== ==== Ratio of earnings (loss) to fixed charges 2.5 -(1) 4.0 6.6 2.1 ==== ===== ==== ====== ==== (1) Earnings were inadequate to cover fixed charges by $665 million in 2002.