How many GB does watching one episode of something take up?

[AnonymousBird]

My Sky plus spectacularly failed to record something I really wanted to watch - not just one episode, but two! I need to catch up fast before it drops off iPlayer, but I have a fairly low limit (10GB) on my monthly usage so wondered how much of a GB an hour of TV takes up on average?

Also, if I download to save for later I assume it is the same amount of GB used - at least if I download I buy some extra time to watch.

And also, it makes no difference (I also assume) whether I watch it on Mac, iphone or whatever as it's the same amount of data to any device....

TIA!

I have several tv episodes downloaded on my iPad- a normal 45 minute episode of Doctor Who takes up about half a Gb, but the two I have in HD are three times that size

OK, that is very helpful. Thanks. I won't do HD to keep it down!

So I've just had a look (even though it's probably a bit late now...)
Taking a random 1 hr masterchef episode:
hd - 4.7Gb
normal - 719Mb
Ipad/TV/tablet - 699Mb