5 - 13 Figure 5-12. TIMBER-CUTTING CHARGE (EXTERNAL) Figure 5-13. FORMULA FOR EXTERNAL TIMBER-CUTTING CHARGE P = D²/40 or P = 0.025D² Where– P = TNT required per target (in pounds) D = Diameter or least dimension of dimensioned timber; in inches Figure 5-14. TIMBER-CUTTING CHARGE (INTERNAL)