Project: Blender Extensions
Tracker: Py Scripts Upload
Script name: Auto Tile Sizes
Wiki page: http://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Render/Auto_Tile_Size
Author(s): Greg Zaal
This addon gives you some quick controls to get the best possible tile sizes for the fastest possible Cycles render. Usually it's a good idea to stick to powers of 2 (16, 64, 256...) to get fast renders, however in the case of tile sizes it's even more important to keep the tiles fairly square and of consistent size. Having some tiles smaller than the rest due to the borders of the image makes for longer renders.
So this addon allows you to choose a target size and then automatically calculates the actual tile dimensions to ensure squareness and consistency.
As a rule of thumb, GPUs like bigger tiles (256 x 256 usually) and CPUs like smaller ones (often 32 square), thus the two target values are stored separately in case you switch between then often. Just remember to hit the Set button!
For a detailed explanation of this reasoning, see this blog post: http://adaptivesamples.com/2013/09/11/auto-tile-size-addon/
At the bottom of the Performance Panel of the render settings are the target tile sizes.
Pick one and hit the Set button to calculate the closest pair of fairly-square dimensions (E.g. for 1080p it's 240x270, 8x4 tiles)
If for some reason you want to set the tile size to exactly the target, resulting in perfectly square tiles but probably not consistent ones, disable Factors Only