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If you are developing virtual products this calculator will be a great asset. Use this calculator to calculate download times for your audio, ebooks, programs or anything else you plan to offer for site visitors to download. You will notice the "Overhead" option. Overhead is very fluid and changes from time to time and server to server. We have found using at least 25% Overhead in our calculations produces pretty realistic download times. There is more information about overhead at the bottom of this page. 

Calculate Download Times

File Size:
Overhead: %

Speed Time
HH:MM:SS
9.6 Kbps
14.4 Kbps
28Kbps
33.6 Kbps
56 Kbps
64 Kbps (ISDN)
128 Kbps (ISDN-2)
256 Kbps
512 Kbps
1.024 Mbps
1.544 Mbps (DS1, T1)
2.048 Mbps (E1, ISDN-32)
10 Mbps (10Base-T)
25.6 Mbps (ATM25)
34 Mbps (E3)
45 Mbps (DS3, T3)
51 Mbps (OC1)
100 Mbps (100Base-T)
155 Mbps (OC3)
622 Mbps (OC12)
1 Gbps (1000Base-T)
2.4 Gbps (OC48)
10 Gbps (OC192)
KByte = Kilobyte
MByte = Megabyte
GByte = Gigabyte
Kbps = Kilobit per second
Mbps = Megabit per second
Gbps = Gigabit per second


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.