Download Mfold

Download the mfold software.

Note that mfold has been replaced by UNAFold, a software package that is much easier to install and run and that offers many more types of computations. Although UNAFold will install without mfold_util, the sir_graph and boxplot_ng programs from the mfold_util package are required in order to obtain structure plots and dot plots from UNAFold. Install mfold_util before installing UNAFold. Versions 3.4 and higher of mfold contains all of the non-interactive programs in mfold_util, so a separate download is not required. Download UNAFold here.

Version 3.6 (and earlier versions) of mfold for Unix, Linux and Mac OS X operating systems is available via a free license for academic and nonprofit use only; commercial use is available for a fee. Copyright © is held by Washington University. Washington University seeks additional licensees for commercial development and marketing and invites all interested parties to submit proposals. Please direct all requests for licensing, information, and limited evaluation copies to Washington University's Office of Technology Management.

Craig Weilbaecher Ph.D.
Business Development Associate
Office of Technology Management (OTM)
Washington University in St. Louis
660 South Euclid Avenue, Campus Box 8013
St. Louis, MO 63110
Tel. no. (314) 747-0685
Fax no. (314) 362-5872
Please send a copy of these requests to Version 3.6 of mfold contains the non-interactive programs from mfold_util version 4.6. It is no longer necessary to download and install mfold_util separately. A separate installation is only required if you wish to run the interactive programs in mfold_util. Questions about the code should be addressed to Dr. Zuker at

NEW! mfold version 3.6 is now available. Download
Download mfold-3.5 binaries: mfold-3.5-Cross-RedHat-binaries.tar.gz Binaries for RedHat Linux. Bin32 binaries Cross-compiled for 32 bit or 64 bit architecture. Bin64 for 64 bit only.
New! mfold_util-4.7: mfold_util-4.7.tar.gz mfold_util-4.5-Linux-binaries.tar.gz
Download mfold_util-4.5 for Mac OS X: mfold_util-4.5-Mac-binaries.tar.gz This gzipped tar file contains binaries that look for the '.col' data files in /usr/local/share/mfold_util. The package may also be configured and built according to local wishes.
Academic License: WORD Text
mfold_util versions 3.3 and beyond run in Unix, Linux (32 or 64 bit architecture) or Mac OS X (Intel or non-Intel)

Old version(s)

Download mfold-3.1: mfold-3.1.2.tar.gz

Those who wish to have the mfold software for the sole purpose of using the OligoArray2 software† are advised to instead download the OligoArrayAux software written by Nick Markham. The current version may be obtained here.

A user manual and other information may be found in or mfold-3.0-manual.pdf.gz. An html version is located at These are preprints of the Zuker, Mathews & Turner chapter below.

  • M. Zuker, D. H. Mathews & D. H. Turner.
    Algorithms and Thermodynamics for RNA Secondary Structure Prediction: A Practical Guide
    In RNA Biochemistry and Biotechnology, 11-43,
    J. Barciszewski and B. F. C. Clark, eds.,
    NATO ASI Series, Kluwer Academic Publishers, Dordrecht, NL, (1999)
  • †J.-M. Rouillard, M. Zuker & E. Gulari.
    OligoArray 2.0: Thermodynamicaly improved oligonucleotide design for microarrays.
    Nucleic Acids Res. 31 (12), 3057-3062, (2003)  [Abstract] [Full Text]