What is the actual formula for converting download times to bps?

I figured it'd be pretty straightforward:

Get total bits by converting bytes to bits
Convert download time to seconds
Divide file size by time to get bps

So I went to this website:

http://www.bluemax.net/techtips/networking/Cable_Modems/Speed/cblmdmdwnload.htm

I entered my numbers in the "reverse DL" section to get the results and it differed from what I calculated.

Here's what I did for a 20MB file:

20MB * 1024 = 20480000000 bits
5:20 = 230 seconds

20480000000 / 230 = 89Kbps / sec

The website says it's actually 729Kbps per sec...

I need more coffee... missing something simple, I'm sure...

Thanks!

-Samson
smartineAsked:
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fixnixCommented:
20MBytes =  (20*1024)KBytes = 20,480 KBytes
20,480 KBytes = (20,480*1024)Bytes = 20,971,520 Bytes
20,971,520 Bytes * 8 bits/Byte = 167,772,160 bits

5:20 = 5*60 + 20 seconds = 320 secs

167,772,160/320 = 524,288bits/sec



I'm going to assume 5:20 is the wrong time however, and that the 230 seconds was the correct time (3:50) which gives the same answer as the website:

167,772,160/230 = 729,444bits/sec

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ngravattCommented:


Mb = MegaBYTES
8 bits = 1 byte

1 Mb = 1024 Kb and 1Kb = 1024 bytes

so 20Mb = 20480 Kb = 20,971,520 bytes = 167,772,160 bits

167,772,160 bits / 230 secs = 729,444 bits/sec

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_anom_Commented:
ngravatt corrected you on the conversion from MB->bits, however 5:20 is 320 seconds, not 230 seconds :)


Cheers
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_anom_Commented:
Ah, someone got it as i typed it in, lol.

Cheers
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smartineAuthor Commented:
Like I said... needed more coffee... :)

Many thanks!

-Samson
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