How to Read the Numbers on Your Internet Connection

Almost every number in this area is published in a unit that isn't the one you need. Not to deceive anyone — the conventions grew up in different industries — but the result is the same: the figure on the box and the figure that matters differ by a factor nobody mentions.

There are four of those mismatches, and one tool for each.

Bits and bytes: the factor of eight

Your connection is sold in bits per second. Files are measured in bytes. There are eight bits in a byte, so the two differ by a factor of eight before anything else happens.

The Download Time Calculator does that conversion and shows its working. A 100 Mbps connection is 12.5 megabytes per second — and a 25 GB download takes 34 minutes, not the few you might expect from a number as large as 100.

The useful habit is the one the tool reports directly: divide your advertised speed by eight and you have the number that actually predicts how long things take. At 100 Mbps you can move about 43.9 GB an hour, which is a far more usable fact than the headline figure.

Lowercase b is bits, uppercase B is bytes. That single letter is the whole difference.

Decimal and binary: the missing 69 GB

The File Size Converter settles the most common storage argument there is: a 1 TB drive really does hold a trillion bytes, and Windows really does report that as 931 GB. Neither is wrong.

The manufacturer counts in powers of ten, where a gigabyte is a billion bytes. The operating system counts in powers of two, where it is 1,073,741,824. Same drive, same bytes, two labels — and a 6.9% gap that grows with capacity, which is why it looks worse on larger drives.

The "missing" space was never there. There is nothing to recover and nothing to fix.

Worth knowing because it turns up everywhere else too: your data allowance is metered in decimal GB, your file browser reports binary, and the two will never quite agree.

A file size is a bitrate budget

Going the other way, the Video Bitrate Calculator turns a size limit into the number your encoder actually asks for.

500 MB for a ten-minute video is a 6,667 kbps total budget. But encoders ask for a video bitrate, and the audio spends the same budget — so the number to type in is 6,539, and handing it the total overshoots by exactly the size of the audio track.

How much that matters depends entirely on how tight the target is. At 500 MB the audio is 1.92% of the budget and you could ignore it. Squeeze the same ten minutes into 25 MB and it takes 38.4%, and at that point ignoring it is the difference between passing and failing an upload limit.

⚠️ One thing the arithmetic will not tell you: resolution decides how good a bitrate looks, not how large the file is. "What bitrate for 1080p" is a judgement, not a calculation.

An allowance is hours of video

The Monthly Data Usage Calculator converts a cap into the only thing it really represents.

Netflix publish their own rates: up to 1 GB an hour in standard definition, 3 GB in HD and 7 GB in 4K. Music is about 0.072 GB an hour. So one hour of 4K costs roughly what a hundred hours of music does.

Which produces the most useful fact in this whole guide:

60 hours of video a month	Data
in HD	180 GB
in 4K	420 GB

Not a minute more watched. One setting, 240 GB — more than many people's entire allowance, and on a phone or small screen the visible difference is close to nothing.

If an allowance keeps being missed, that is where to look first. The second place is the background: system and game updates, cloud photo backup and autoplay previews, where a single game update can be 50 GB arriving with no warning.

The short version

• Divide your speed by eight. 100 Mbps is 12.5 MB/s.
• Lowercase b is bits, uppercase B is bytes.
• A 1 TB drive showing 931 GB is correct — decimal against binary, a fixed 6.9%.
• Subtract the audio before setting a video bitrate.
• Video quality beats every other data saving, by a wide margin.
• Your provider's usage page is the only authoritative number. These tools decide what to change.

Each has a printable. The bits-and-bytes conversion is the one worth committing to memory, because it is the mismatch you will meet most often and the easiest to correct for in your head.