What Is Download Speed? Mbps vs MB/s Explained
Download speed is how quickly data travels from the internet to your device. Every web page, video, app update or photo you open has to be downloaded first, so this is the number most people think of when they talk about “internet speed”.
How download speed is measured
Download speed is a rate: an amount of data per second. Internet providers and speed tests almost always use megabits per second (Mbps).
- 1 megabit (Mb) = 1,000,000 bits
- 1 gigabit per second (Gbps) = 1,000 Mbps
- 1 kilobit per second (Kbps) = 0.001 Mbps
A bit is the smallest unit of data, a single 0 or 1. Computers usually store files in bytes, and one byte is eight bits. That difference causes a lot of confusion.
Mbps vs MB/s: why your download looks “slower”
Your browser or game launcher usually shows download progress in megabytes per second (MB/s), with a capital “B”. Internet plans are sold in megabits per second (Mbps), with a small “b”.
To convert, divide by eight:
| Plan speed (Mbps) | Best-case download rate (MB/s) |
|---|---|
| 10 Mbps | about 1.25 MB/s |
| 50 Mbps | about 6.25 MB/s |
| 100 Mbps | about 12.5 MB/s |
| 500 Mbps | about 62.5 MB/s |
| 1,000 Mbps (1 Gbps) | about 125 MB/s |
So a 100 Mbps connection that downloads a game at 11–12 MB/s is working normally. Real downloads are a little lower than the “best case” because some capacity is used by the network protocols that carry the data (headers, acknowledgements and so on). Our download time calculator does this maths for you.
What counts as a good download speed?
It depends on what you do and how many people share the connection. Streaming services publish their own recommendations per stream:
| Activity | Typical recommendation |
|---|---|
| HD video (720p) | about 3 Mbps (Netflix), about 2.5 Mbps (YouTube) |
| Full HD (1080p) | about 5 Mbps (Netflix and YouTube) |
| 4K Ultra HD | about 15 Mbps (Netflix), about 20 Mbps (YouTube) |
Those figures are per stream. A household where two people watch 4K while someone else joins a video call needs much more than one person browsing alone. Our How much speed do I need? tool adds this up for you.
As a rough guide:
- Under 10 Mbps: browsing and one HD stream work, but things slow down quickly when several devices are busy.
- 25–100 Mbps: comfortable for most small households, including 4K streaming.
- 100 Mbps and above: large households, frequent big downloads, and many devices at once.
- 1 Gbps: very fast downloads of large files. Most single activities cannot use this much on their own.
Why your download speed changes
The same connection can give different results within minutes. Common reasons:
- Wi-Fi. Distance, walls and interference from neighbours’ networks often limit speed far more than your plan does. A cable connection removes this factor. See how to improve your Wi-Fi.
- Other devices. A console update or a cloud backup running in the background takes a share of the connection.
- Busy hours. In the evening, more people in your area are online, and parts of your provider’s network can become congested.
- Your device. Older phones, laptops and network adapters can be slower than a fast fibre line.
- The server. Every test measures the path to a particular server. A slow or distant server gives a lower number than your line can really do.
How SpeedCheckWeb measures download speed
When you press Start, your browser downloads random data from the nearest Cloudflare data centre for 5–12 seconds. It counts every byte as it arrives, uses several requests at once on fast connections, and ignores the first part of the transfer, while the connection is still speeding up. The result is the average speed over the rest of the test. The methodology page explains each step.
In short: download speed is how fast data reaches you, measured in Mbps. Divide by eight to get the MB/s your downloads show. What counts as “enough” depends on how many people and devices share your connection.
Sources
- Netflix Help Center – Internet connection speed recommendations
- YouTube Help – System requirements (recommended sustained speeds)
Figures from third parties can change; we review guides regularly. See our editorial policy.