The minimum average size of the transaction in RecordsKeeper is 250 bytes, and the maximum size of Block is 8 MB (8388608 bytes). Thus you can have up to 33554 transactions per Block on an average. The average Block time is 15 seconds. So you can have up to 2236 transaction/sec. But this is considering if we have all the smallest size transaction. If the transaction size is higher, this number can go down.