With the launch date approaching there has been an increasing number of questions concerning how to calculate mining rate. One method of benchmarking is described in detail at https://benchmark.minezcash.com/index.php?title=Talk:Main_Page, however that will only tell you how quickly your computer performs, without giving a real-world measure of speed.
To get a rough estimate of your mining rate compared to the state of network, you can use a simple Python script available at https://github.com/JanKalin/zcutils. Currently the script only works with the data from zcashd as it reads transactions from the blockchain. The standalone miners are not supported.
Check out the mean difficulty and the blocks/day values. In the example the vales are 443.44 and 38.7. So, assuming the difficulty in the network will increase by a factor of 10 (or 100), the expected number of blocks per day will fall to 3.9 (or 0.4).