Your actual transfer speeds will likely be a bit slower than the calculator shows. Why? Because on a normal Internet connection your transfer speed is decreased by:
Variable speed quality influenced by latency and jitter.
Physical signaling overhead (e.g. The advertised transfer speed of a T1 line is 1,536 Kbps however 192 Kbps is usually tied up in the T1 line signaling protocol so the best you'll ever get is 1,344 Kbps)
Layer 4 transport and transmission protocol maintainence/overhead. Amazingly, these below processes can eat up to 10% of your transfer speed.
Handshaking negotiation procedures between you and the place you are transferring the file such as "slow start" described technically in RFC 2001.
TCP overhead, error checking and sending of protocol headers (e.g. Each IPv4 header is 160 bits, each UDP header is 64 bits, etc.)
If you are not transferring files over the Internet (TCP/IP) then these things will impact you less.