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How to obtain AmberTools20

AmberTools is a free, useful standalone package and a prerequisite for installing Amber itself. The AmberTools suite is free of charge, and its components are mostly released under the GNU General Public License (GPL). A few components are included that are in the public domain or which have other, open-source, licenses. The libsander and libpbsa libraries use the LGPL license.

Option 1: Getting source code in tar format

This is the traditional way AmberTools has been distributed. It is recommended for most new users, and is the required path if you also want to get Amber. AmberTools is distributed in source code format, and must be compiled in order to be used. You will need C, C++ and Fortran90 compilers.

The Reference Manual is available in pdf format, and included in the distribution. It may help you to see if AmberTools meets your needs.

To download version 20 of the AmberTools distribution, please fill in the following form and click the "Download" button. The file size you should get is about 450 MB, and the md5sum is 8c1fe81833796a9cb823019e02c522e0.

Note: Installation instructions are in Chapter 2 of the Amber 2020 Reference Manual. More detailed instructions for many machines may be found at simplified requirements for MacOS, Linux and Windows 10.




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Option 2: Binary distribution via conda

This is a relatively new option: the conda package-management system can install a serial, binary (pre-compiled) distribution as follows:

  • If you don't have conda installed, please visit the Miniconda download page. (You should choose the python 3.7 option.)

  • Those with an existing conda installation may wish to create a new conda "environment" to avoid conflicts with what you already have installed. To do this:

      conda create --name AmberTools20
      conda activate AmberTools20

    (Note that you would need to perform the "conda activate" step every time you wish use AmberTools20 in a new terminal; it might be appropriate to add this to your start-up script. Creating a new environment should not be necessary if you only use conda for AmberTools.)

  • Once this is done, type:

      conda install -c conda-forge ambertools=20

This should work for Linux and MacOS systems, but it does not provide access to parallel or gpu-optimized codes. It provides a simple way to get started with AmberTools, and to install it into many workflows, but is not a substitute for the full source-code distributions listed above.

Thanks to Jaime Rodríguez-Guerra, the Chodera lab, and Simon Bray for spearheading this.

How to obtain Amber20

Amber20 facilitates faster simulations (on parallel CPU or GPU hardware) and is distributed with a separate license and fee structure. Click here for the Amber 20 License Agreement (PDF). Print this form, fill it out, sign and return (with your payment) to the address given at the bottom of the license agreement. Once your order is processed, you will receive download information via email. PDF versions of the Reference Manual are included in the download.

Please note: The Amber20 license is a site license, valid for any number of users and any number of computers. The computers may be located anywhere (such as in the "cloud", or at remote computing centers.) There are restrictions on using the codes on behalf of others who do not have an Amber license; see the license document for details.

Also note: Each release of Amber (which happens every two years) is treated as separate product, and requires a new license form and a new fee.


  • Academic/non-profit/government: $500 (US dollars).
  • Industrial (for-profit): $20,000 for new licensees, $15,000 for licensees of Amber 18.
  • Porting and demonstration licenses are available, as are licenses for computing centers: see the License Agreement for details.
  • Custom payment schedules or subscription-based approaches can be arranged: please send email to for more information.)

  • People who licensed Amber18 after January 1, 2020 are eligible for a free upgrade to Amber20. (This is not automatic: if you wish to obtain the new version, you need fill out and submit a new License Agreement, indicating that you are eligible for the upgrade.)

Payment for all orders for Amber must received prior to shipment of the Software. Payment must be via bank transfer, paper bank check or paper money order in USD, or Visa, MasterCard or American Express credit card. Make payments to: Regents, University of California. We are sorry, but purchase orders can no longer be accepted.

Once payment is received, an email will be sent to the address provided by the customer on the License Agreement containing a username and password, along with instructions on how to download the software.

Fee Waivers

Waivers for the license fee are available for scientists outside of North America, Western Europe and Japan. Please send email to, explaining your situation, and your need for the pmemd program (all other parts of Amber are available for free).

"How's that for maxed out?"

Last modified: Jul 9, 2020