Fragments are blocks of unused memory. To give an indication of whether fragmentation is causing a problem for your application, ANTS Memory Profiler looks at the following:

• Fragmentation ratio = size of the largest fragment : total size of all fragments 
• Free space ratio = total size of all fragments : total memory allocated to your application
• Number of fragments larger than 64k 

Depending on these ratios, an appropriate message is displayed:

• Memory fragmentation is restricting the size of objects that can be allocated.
  The fragmentation ratio is less than 0.3:1, ie, the largest fragment is very small.
• Memory fragmentation is affecting the size of the largest object that can be allocated.
  The fragmentation ratio is less than 0.6:1, and greater than 0.3:1, ie, the largest fragment is fairly small.  
• Memory fragmentation may be causing .NET to reserve too much free memory.
  The free space ratio is greater than 0.7:1, and there are more than three fragments larger than 64k.
  ie, most of your application's memory is free space, and there are several large fragments.
• Memory fragmentation may be causing .NET to reserve too much free memory.
  The free space ratio is less than 0.7:1, and greater than 0.4:1, and there are more than three fragments larger than 64k.
  ie, a large amount of your application's memory is free space, and there are several large fragments. 
• There are many large fragments; fragmentation may become an issue over time.
  There are more than ten fragments larger than 64k.
• No problems with large object heap fragmentation are detected.