Thomson Reuters have released their 2011 Journal Citation Reports and these are summarised below. Acta Crystallographica Section D leads the crystallography rankings with its highest ever impact factor of 12.6 and the top immediacy index. Both with cited half-lives of more than 10 years, the Journal of Applied Crystallography has increased its impact factor to 5.2 and Acta Cryst. B to 2.3. The Journal of Synchrotron Radiation has risen up in the rankings of journals in the instruments and instrumentation category with a new impact factor of 2.7.
| 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001 | 2000 | 1999 | 1998 | 1997 | |
| Acta Crystallographica Section A | 2.076 | 54.33 | 49.93 | 2.051 | 2.385 | 1.676 | 1.791 | 1.829 | 1.558 | 1.417 | 1.749 | 1.491 | 1.601 | 2.146 | 1.806 |
| Acta Crystallographica Section B | 2.286 | 1.829 | 1.801 | 2.341 | 2.163 | 2.172 | 1.910 | 5.418 | 3.643 | 2.026 | 1.955 | 1.734 | 1.700 | 1.612 | 1.463 |
| Acta Crystallographica Section C | 0.518 | 0.745 | 0.782 | 0.561 | 0.719 | 0.896 | 0.777 | 0.728 | 0.828 | 0.659 | 0.570 | 0.543 | 0.581 | 0.577 | 0.459 |
| Acta Crystallographica Section D | 12.619 | 6.326 | 2.257 | 2.943 | 2.620 | 1.687 | 1.401 | 1.693 | 2.208 | 1.760 | 2.124 | 3.067 | 2.935 | 2.244 | 2.118 |
| Acta Crystallographica Section E | 0.347 | 0.413 | 0.411 | 0.367 | 0.508 | 0.567 | 0.581 | 0.491 | 0.453 | ||||||
| Acta Crystallographica Section F | 0.506 | 0.563 | 0.551 | 0.606 | 0.645 | ||||||||||
| Journal of Applied Crystallography | 5.152 | 3.794 | 3.018 | 3.212 | 3.629 | 2.495 | 5.248 | 3.534 | 2.324 | 1.871 | 2.583 | 1.752 | 1.901 | 1.569 | 1.988 |
| Journal of Synchrotron Radiation | 2.726 | 2.335 | 1.994 | 2.333 | 2.978 | 2.38 | 2.392 | 1.919 | 1.144 | 0.885 | 1.519 | 0.924 | 1.114 | 1.874 | 1.688 |
Impact factors are generally calculated based on a three-year period. For example, the 2011 impact factor for a journal would be calculated as follows:
where A = number of times articles published in 2009-2010 were cited in tracked journals during 2011 and B = number of articles published in 2009-2010.