Approximate Log(Gamma(X))

TOMS291, a C library which approximates the logarithm of the Gamma function.

The text of many ACM TOMS algorithms is available online through ACM: or NETLIB:


The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.


TOMS291 is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:

POLPAK, a C library which evaluates a variety of special functions.

TEST_VALUES, a C library which tabulates several values of a variety of special functions.



  1. Malcolm Pike, David Hill,
    Algorithm 291: Logarithm of Gamma Function,
    Communications of the ACM,
    Volume 9, Number 9, September 1966, page 684.

Source Code:

Last revised on 19 August 2019.