Velocity Reviews > A question of maths

# A question of maths

Philip
Guest
Posts: n/a

 04-14-2006
How do I work out how long it would take do download a certain amout of
data at a given nominal speed?

Say I have a 100 MB file to download and I am connected at 256 kBit/s.
What's the easy equation? And how do I scale this to work out times at
different speeds.

I know the real speeds achieved differ from what's advertised, but I
want first to consider the theoretical perfect transfer.

Philip

MarkH
Guest
Posts: n/a

 04-14-2006
Philip <(E-Mail Removed)> wrote in news:44402a79\$(E-Mail Removed):

> How do I work out how long it would take do download a certain amout of
> data at a given nominal speed?
>
> Say I have a 100 MB file to download and I am connected at 256 kBit/s.
> What's the easy equation? And how do I scale this to work out times at
> different speeds.

256Kbit/s divided by 8
= 32 KB/s x 60
= 1920KB/minute x 60 / 1024
= 112.5 MB/hour

In practical terms if you get pretty good speeds 30KB/s or better than you
110 MB per hour then you are getting close to the theoretical maximum
speed.

--
Mark Heyes (New Zealand)
See my pics at www.gigatech.co.nz (last updated 5-September-05)
"The person on the other side was a young woman. Very obviously a
young woman. There was no possible way she could have been mistaken
for a young man in any language, especially Braille."

Jerry
Guest
Posts: n/a

 04-15-2006
MarkH wrote:
> Philip <(E-Mail Removed)> wrote in news:44402a79\$(E-Mail Removed):
>
>
>>How do I work out how long it would take do download a certain amout of
>>data at a given nominal speed?
>>
>>Say I have a 100 MB file to download and I am connected at 256 kBit/s.
>>What's the easy equation? And how do I scale this to work out times at
>>different speeds.

>
>
> 256Kbit/s divided by 8
> = 32 KB/s x 60
> = 1920KB/minute x 60 / 1024
> = 112.5 MB/hour
>
> In practical terms if you get pretty good speeds 30KB/s or better than you
> could expect to download 100MB in about an hour or so. If you get 105 -
> 110 MB per hour then you are getting close to the theoretical maximum
> speed.

why the 1024? A megabyte is 1 million bytes; 1000 x 1000; 1,000,000 bytes.

Stephen Williams
Guest
Posts: n/a

 04-15-2006

>
> why the 1024? A megabyte is 1 million bytes; 1000 x 1000; 1,000,000
> bytes.
>

Have Western Digital paid you to say that?

Steve

Murray Symon
Guest
Posts: n/a

 04-15-2006
On Sat, 15 Apr 2006 13:44:38 +1200, Jerry wrote:

> MarkH wrote:
>> Philip <(E-Mail Removed)> wrote in
>> news:44402a79\$(E-Mail Removed):
>>
>>
>>>How do I work out how long it would take do download a certain amout of
>>>data at a given nominal speed?
>>>
>>>Say I have a 100 MB file to download and I am connected at 256 kBit/s.
>>>What's the easy equation? And how do I scale this to work out times at
>>>different speeds.

>>
>>
>> 256Kbit/s divided by 8
>> = 32 KB/s x 60
>> = 1920KB/minute x 60 / 1024
>> = 112.5 MB/hour
>>
>> In practical terms if you get pretty good speeds 30KB/s or better than
>> 105 - 110 MB per hour then you are getting close to the theoretical
>> maximum speed.

>
> why the 1024? A megabyte is 1 million bytes; 1000 x 1000; 1,000,000
> bytes.

cue flame war ... (but yes, you're right Jerry).

In reality you can use either figure as it is only an estimation and
your Internet speed is likely to be the most variable factor, anyway.

MarkH
Guest
Posts: n/a

 04-15-2006
Jerry <(E-Mail Removed)> wrote in news:44404d66\$(E-Mail Removed):

> MarkH wrote:
>> Philip <(E-Mail Removed)> wrote in
>> news:44402a79\$(E-Mail Removed):
>>
>>
>>>How do I work out how long it would take do download a certain amout
>>>of data at a given nominal speed?
>>>
>>>Say I have a 100 MB file to download and I am connected at 256
>>>kBit/s. What's the easy equation? And how do I scale this to work out
>>>times at different speeds.

>>
>>
>> 256Kbit/s divided by 8
>> = 32 KB/s x 60
>> = 1920KB/minute x 60 / 1024
>> = 112.5 MB/hour
>>
>> In practical terms if you get pretty good speeds 30KB/s or better
>> you get 105 - 110 MB per hour then you are getting close to the
>> theoretical maximum speed.

>
> why the 1024? A megabyte is 1 million bytes; 1000 x 1000; 1,000,000
> bytes.

Is that a special size for pedants, or are you talking about common usage?

Try this:
Right click a large file and select properties, check size.
In Windows: 349MB (366,231,552 bytes)
In Linux: 349.3MB (366,231,552 bytes)

In common usage 1MB=1024x1024

--
Mark Heyes (New Zealand)
See my pics at www.gigatech.co.nz (last updated 5-September-05)
"The person on the other side was a young woman. Very obviously a
young woman. There was no possible way she could have been mistaken
for a young man in any language, especially Braille."

-=rjh=-
Guest
Posts: n/a

 04-15-2006
Philip wrote:
> How do I work out how long it would take do download a certain amout of
> data at a given nominal speed?
>
> Say I have a 100 MB file to download and I am connected at 256 kBit/s.
> What's the easy equation? And how do I scale this to work out times at
> different speeds.
>
> I know the real speeds achieved differ from what's advertised, but I
> want first to consider the theoretical perfect transfer.

It's been done a thousand times before, writing a javascript calculator
is trivial, so there are heaps of these on the web.

http://www.t1shopper.com/tools/calcu...lculator.shtml

http://www.intel.com/personal/resour...calculator.htm

Enkidu
Guest
Posts: n/a

 04-15-2006
Philip wrote:
> How do I work out how long it would take do download a certain amout of
> data at a given nominal speed?
>
> Say I have a 100 MB file to download and I am connected at 256 kBit/s.
> What's the easy equation? And how do I scale this to work out times at
> different speeds.
>
> I know the real speeds achieved differ from what's advertised, but I
> want first to consider the theoretical perfect transfer.
>

256kbps is 256 x 1024 bits per sec = 262144 bps = 32768 Bytes per second.

100Mb = 104,857,600 Bytes

Therefore 100Mb at 32768 bytes per second = 104857600 / 32768

= 3200 second = 53 minutes and 20 seconds.

I've used a scaling factor of 1024 = 1k. In some circumstances 1k may be
1000 units.

To look at it another way, 256kbps = 32kB/sec and you want to transfer
100MB or 102,400kB. That gives a transfer time of 3200 seconds. Amazing!

Cheers,

Cliff

Stephen Worthington
Guest
Posts: n/a

 04-15-2006
On Sat, 15 Apr 2006 02:24:19 GMT, MarkH <(E-Mail Removed)> wrote:

>Jerry <(E-Mail Removed)> wrote in news:44404d66\$(E-Mail Removed):
>
>> MarkH wrote:
>>> Philip <(E-Mail Removed)> wrote in
>>> news:44402a79\$(E-Mail Removed):
>>>
>>>
>>>>How do I work out how long it would take do download a certain amout
>>>>of data at a given nominal speed?
>>>>
>>>>Say I have a 100 MB file to download and I am connected at 256
>>>>kBit/s. What's the easy equation? And how do I scale this to work out
>>>>times at different speeds.
>>>
>>>
>>> 256Kbit/s divided by 8
>>> = 32 KB/s x 60
>>> = 1920KB/minute x 60 / 1024
>>> = 112.5 MB/hour
>>>
>>> In practical terms if you get pretty good speeds 30KB/s or better
>>> you get 105 - 110 MB per hour then you are getting close to the
>>> theoretical maximum speed.

>>
>> why the 1024? A megabyte is 1 million bytes; 1000 x 1000; 1,000,000
>> bytes.

>
>Is that a special size for pedants, or are you talking about common usage?
>
>Try this:
>Right click a large file and select properties, check size.
>In Windows: 349MB (366,231,552 bytes)
>In Linux: 349.3MB (366,231,552 bytes)
>
>In common usage 1MB=1024x1024

Actually, that is now wrong. There is a proper standard for binary
prefixes that work alongside SI prefixes. Everybody should now be
doing it right, so there will be no confusion:

SI Prefixes (decimal):
http://physics.nist.gov/cuu/Units/prefixes.html

IEC binary prefixes:
http://physics.nist.gov/cuu/Units/binary.html

so 1 MB is 1,000,000 bytes and 1 MiB is 1,048,576 bytes.

MarkH
Guest
Posts: n/a

 04-15-2006
Stephen Worthington <(E-Mail Removed)34.nz56.remove_numbers> wrote in
news:(E-Mail Removed):

> On Sat, 15 Apr 2006 02:24:19 GMT, MarkH <(E-Mail Removed)> wrote:
>
>>In common usage 1MB=1024x1024

>
> Actually, that is now wrong. There is a proper standard for binary
> prefixes that work alongside SI prefixes. Everybody should now be
> doing it right, so there will be no confusion:
>
> SI Prefixes (decimal):
> http://physics.nist.gov/cuu/Units/prefixes.html
>
> IEC binary prefixes:
> http://physics.nist.gov/cuu/Units/binary.html
>
> so 1 MB is 1,000,000 bytes and 1 MiB is 1,048,576 bytes.

Actually you are wrong. In common usage 1MB IS 1,048,576!

In technically correct usage MiB would be used, but I have seen no evidence
that the common usage has moved to the technically correct prefix.

--
Mark Heyes (New Zealand)
See my pics at www.gigatech.co.nz (last updated 5-September-05)
"The person on the other side was a young woman. Very obviously a
young woman. There was no possible way she could have been mistaken
for a young man in any language, especially Braille."