What broadband speeds mean: download, upload and the bit you feel

A broadband speed is a rate: how much data can move in a second. Providers advertise it in megabits per second, written Mbps. The figure people remember is download, because that is what fills a screen. Upload is the quieter number, and it is the one that fails a working day first.

Bits, bytes, and the advert

A bit is the small unit. A byte is eight bits. Broadband adverts use megabits. Computer files are usually sized in megabytes or gigabytes. Divide the advertised megabits by eight before you compare them with a file size, and expect real transfers to be slower than that clean sum because of overheads. A “100 meg” package is not a 100 megabyte-per-second pipe.

Those times are arithmetic, not a promise. A website, a Wi-Fi hop, or a busy evening can miss them by a long way. Use the table to stop mixing units. Do not use it as a guarantee.

Download and upload are different jobs

Download is data arriving: films, pages, updates, music. Upload is data leaving: a video call’s picture of you, a backup, a file you send to a client, a doorbell camera. A product can be generous on download and mean on upload. That was common on part-fibre. If your complaint is “the call freezes when I share a screen”, read the upload figure before you buy a larger download.

Latency, the delay, is a third number and it is not the same as bandwidth. Games and calls feel delay even when a speed test looks large. This site will not invent a millisecond for your address. If a provider publishes a latency claim, read it as their claim.

The line and the Wi-Fi

The line ends at the router. Wi-Fi starts there. A phone at the back of the house is not measuring the product you bought. It is measuring radio, walls, and whatever else is using the same air. Plug a laptop into the router with an Ethernet cable and run the test again if you want a fairer view of the line. If the cable test is close to the package and the phone is not, the next purchase is placement or Wi-Fi, not a faster tier.

• Put the router in the open, not in a cupboard or on the floor behind a television.
• Prefer a cable for a desktop, a console, or a work laptop that never moves.
• If several people work at once, look at upload and at how the Wi-Fi is shared, not only the headline download.
• Replace the story “the broadband is slow” with which test, on which device, at what time.

How much is enough

One high-definition stream is modest next with current packages. Several streams, large game updates and a backup at the same time are not. There is no single national number that fits a household, and this article will not invent one. Match the tier to the thing that currently fails: a stalled upload, a copper line that never reaches the advert, or a contract that costs more than a slower product you would actually use.