Ethash is a heavyweight PoW algorithm used by the most popular cryptocurrencies, including Ethereum, Ethereum Classic, as well as MOAC, Expanse, Pirl, etc. The algorithm is different, because it uses the DAG file that is loaded into GPU memory at the moment of miner launch. An epoch change takes place every 30000 blocks and leads to an increase in size of the DAG file by 8 MB.
Ethash cryptocurrencies are mined using NVIDIA and AMD graphics cards and also the ASIC miners. For Ethereum and Ethereum Classic 3GB GPU memory is already not enough as it could not store the DAG file. 4GB or more GPU memory is required to mine ETH and ETC. Please note that the Ethereum network usually has a significant value of transaction fees included into each block. The calculator takes the average value of the transaction fees into account while calculating ETH mining profitability.