Internet speed detection in swift - ios

Question

I am trying to detect speed of my internet using NSURLConnection. What I do is, I start downloading a file, in delegates of NSURLConnection, I start a time and then when the download finishes, it gets the time frame as well as the data received and then I calculated to get the mb/sec using the below code.
if (startTime != nil) {
elapsed = NSDate().timeIntervalSinceDate(startTime)
NSLog("\(length) -- \(elapsed)")
var d = (Double(length) / elapsed)
var result = CGFloat( d/1024)
result = result * 0.0078125
result = result * 0.0009765625
return result
}
My question is why I am dividing 1024 here because If I don't do I get something is bits/bytes...
I am assuming I am getting seconds from NSDate().timeIntervalSinceDate(startTime) and bytes from Nsdata length
I think I am getting right value however I am not sure. Let me know why it's necessary to divide 1024!

Answer 1

I was dividing by 1024 in the example you took this from simply because I think looking at bytes per second yields a number that is too large to make sense of (and it suggests a misleading degree of accuracy given the variability in that number).
By dividing by 1024, you get kilobytes per second. To get megabytes per second, you'd divide by 1024 * 1024. The 1024 in that original code sample was a mistake, as that would yield kilobytes per second.
So, use whatever measurement you want. Bytes per second, kilobytes per second, megabytes per second. Or you can multiply megabytes per second by 8 and get megabits per second (another common measure of speed). Just divide the bytes per second by the appropriate factor.