The quick and dirty way of calculating the throughput of a blockchain is as follows:
For Bitcoin, the transaction throughput is about 7tx/second. This is because of the relatively small block and the very long block time. Ethereum has short block times but very tiny blocks and ends up at about 14tx/second. Blockchains such as Stellar, Bitshares, and Waves can reach speeds of over, 1000tx/second.