How it works

Short version: you type numbers, your browser does the maths, and you get an answer with the formula beside it. Here is what is going on underneath.

Start with your question

Use the Internet Speed Calculator for an overall picture, the transfer tools for a file or a backup, and the data tools for a monthly allowance. The network tools explain the things a plain speed number cannot, such as ping, jitter and Wi-Fi sharing.

Bits versus bytes in 30 seconds

Providers advertise speed in megabits per second (Mbps). Files and downloads are usually shown in megabytes per second (MB/s). Eight bits make one byte, so divide Mbps by 8 for a rough MB/s value. A 100 Mbps plan moves about 12.5 megabytes every second.

Speed, data and delay are three different things

• Speed (Mbps) is how fast data can arrive right now.
• Data (GB) is how much you use over time and what a data cap counts.
• Latency (ms) is the delay of a round trip. It decides how live apps feel.

Where our numbers come from

The formulas are standard unit conversions and well-known rules of thumb, such as about 5 Mbps for an HD stream and about 25 Mbps for 4K. Where a value is an assumption, such as 10% overhead on a download, the tool page says so and lets you change it.

Why results are estimates

Wi-Fi quality, distance, other devices, the server you connect to and congestion on the network all change what you actually get. Treat our results as a solid starting point and leave some headroom.