The information you are looking for is available here: http://ark.intel.com/products/76086/Intel-Core-i7-4850HQ-Processor-6M-Cache-up-to-3_50-GHz and here: http://en.wikipedia.org/wiki/List_of_Intel_Core_i7_microprocessors
In this case the answer is 6 MB.
Also to avoid future questions of this kind you can try the followings before posting:
-Google search your CPU model and visit the page from ark.intel.com that is returned as result, the information is provided there, look for Intel Smart Cache in that page to get your answer.
-Alternatively you can search on Wikipedia. First you need to search for the model (Intel Core i3, Intel Core i5 or Intel Core i7 or any other you are interested on), then search for the exact model you are having on the resulted page. Usually the information is presented in a table.