Abstract: A method and apparatus for the calculation of the reciprocal of a normalized mantissa M for a floating-point input number D. A formula for determining the minimum size for the look-up table in accordance with the required precision is provided, as well as formulas for calculating look-up table entries. The look-up table stores the initiation approximations and the correction coefficients, which are addressed by the corresponding number of the mantissa's most significant bits and used to obtain the initial approximation of the reciprocal by means of linear interpolation requiring one subtraction operation and one multiplication operation. The result of the linear interpolation may be fed to a Newton-Raphson iteration device requiring, for each iteration, two multiplication operations and one two's complement operation, thereby doubling the precision of the reciprocal.