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Standard User camieabz
(legend) Mon 02-May-11 09:49:59
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Files size to speed calc


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Trying to remember the way to calc a speed from filesize and time taken (don't tell me to use the TBB meter).

Is it as simple as:

100MB = 800Mb

Divided by time in seconds (pretend 200 secs).

4Mbp/s


Surely not that simple?

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Standard User john2007
(legend) Mon 02-May-11 10:48:47
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Re: Files size to speed calc


[re: camieabz] [link to this post]
 
That's the way I'd measure speed. It shows the rate at which you are receiving usable data. Your actual sync rate would be higher to account for the overheads.
Standard User RobertoS
(sensei) Mon 02-May-11 17:39:58
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Re: Files size to speed calc


[re: camieabz] [link to this post]
 
As john says, but only in a way.

If you want to measure the data speed then that is all there is to do.

But if you want to compare the speed to a sync speed or IP Profile then No. Or "Maybe not" frown.

File sizes are measured as 1K bytes = 1024 bytes and 1MB = 1024KB. Other than tbb speed test, (possibly Ookla as well?), transmission speeds are 1Kbps = 1000bps and 1Mbps = 1000Kbps. (The speed test and graph bars in tbbMeter use 1000).

ADSLx IP Profiles seem to use 1000, but Openreach are saying something about the publicised speeds on FTTC being data speeds. The exact meaning of that is still a bit unclear to me, especially as the top IP profile is 38717Mbps at a high 30s Mbps sync.

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Standard User orly
(fountain of knowledge) Mon 02-May-11 17:52:08
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Re: Files size to speed calc


[re: camieabz] [link to this post]
 
Yep.

The trick is just knowing the units and how to convert them. It's pretty easy to get them wrong or mixed up no matter who you are. As long as you get everything in a common unit then it's relatively simple maths.

So, downloading a 1GB iso file on a 2.5Mbit connection. Just rearrange so it's 1000MB on a 0.31MB connection. 1000/0.31 = 3225 secs (about 54 minutes)

I'd suggest that about 90% or more of the population wouldn't have the faintest idea how to do the above conversions and calculation though which is an indictment of our education system.

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Standard User XRaySpeX
(knowledge is power) Mon 02-May-11 18:41:48
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Re: Files size to speed calc


[re: orly] [link to this post]
 
In reply to a post by orly:
1000/0.31 = 3225 secs (about 54 minutes)
Or even 3436 secs (about 57 mins) if you really wanted to do it accurately by accounting for storage in powers of 2 and transmission speeds in powers of 10.

And even then both these calculations are based only on throughput speeds. If you were using your actual connection (Sync) speed as the yardstick, then these timings would need to increase by about 20% to 4123 secs (about 69 mins).

I'm sure that the majority of those who were interested in such matters would be able to make a reasonable fist of arriving at a sufficient approximation.

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Standard User 5km
(knowledge is power) Mon 02-May-11 18:53:25
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Re: Files size to speed calc


[re: camieabz] [link to this post]
 
Google can answer that with a search

Google: 100MB / 200 seconds in Mbps

http://www.google.co.uk/#sclient=psy&hl=en&biw=1472&...

Simples!

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