Humidity wise they they are in within 1%, when I used the test kit I did not have to calibrate. I have two IR guns (included links for those below) I just tested them before posting them. Currently the temp on my gauge is 87.4, the temp on the IR from Amazon is 87.9, and the one from Reptile Basics is 86.4, so I would consider this particular combo accurate.
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1
http://www.reptilebasics.com/pe-2