Press Start and the test runs in your browser. It first sends small requests to find your ping, then downloads and uploads files of growing size (100 kB up to 25 MB) until each transfer takes long enough to measure properly. Your result is the speed those transfers reached, shown in megabits per second (Mbps), the unit internet providers use in their plans.
The test talks to the nearest Cloudflare data centre, which is usually only a few milliseconds away, so it measures your own line rather than a slow server on the other side of the world. Nothing you do on the page is stored on this site.
Two numbers matter most for everyday use. Download speed decides how fast pages, videos and files arrive. Upload speed decides how quickly your photos, backups and video call picture leave your home. Ping and jitter decide how responsive the connection feels, which is what gamers and people on video calls notice first.
How to use the Internet Speed Test
- Close other tabs and pause downloads, backups and streams on the same network.
- Choose Typical speed for the speed you get most of the time, or Peak speed for the best your line reaches.
- Press Start test. Ping is measured first, then download and upload. The gauge shows the live speed.
- Read your results and the checklist underneath, which shows what the connection can handle. Copy results puts them on your clipboard.
Test traffic goes straight from your browser to Cloudflare’s speed test servers. Your last five results are kept only in this browser so you can compare them.
How it works
Each download and upload is timed in the browser. The bits transferred are divided by the transfer time, and the result for each direction is the median of all valid transfers (or the 90th percentile if you choose peak speed). Ping comes from 20 tiny requests sent while the line is idle, and jitter is the average difference between consecutive pings. Latency is measured again while the download and upload are running, which shows how much your connection slows down when it is busy.
What speed do you need?
| Activity | Download | Upload | Ping |
|---|---|---|---|
| Web browsing and email | 5 Mbps | 1 Mbps | Under 100 ms |
| HD video (1080p) on Netflix | 5 Mbps | Any | Any |
| 4K video on Netflix | 15 Mbps | Any | Any |
| HD group video call on Zoom | 3 Mbps | 3 Mbps | Under 100 ms |
| Online gaming | 10 Mbps | 3 Mbps | Under 50 ms |
| Household of 3 to 4 people | 100 Mbps | 20 Mbps | Under 50 ms |
Streaming and call figures are the providers’ own recommendations for a single stream. Add them up for every person using the connection at the same time.
How to get an accurate result
- Plug a computer into the router with an Ethernet cable to measure the line itself rather than your Wi-Fi.
- Pause other downloads, game updates, cloud backups and streams in the house while the test runs.
- Run the test two or three times, and at different times of day. Evening slowdowns point to congestion at your provider.
- On Wi-Fi, test close to the router and again in the room where you usually work, so you can see how much the signal drops.
- Restart the router if the result is far below your plan, then test again before calling your provider.
Formula
Speed (Mbps) = bytes transferred × 8 ÷ transfer time in seconds ÷ 1,000,000 · Ping = median round-trip time of 20 small requests · Jitter = average change between one ping and the next
Worked example
A 25 MB test file (25,000,000 bytes) downloads in 1.6 seconds. That is 25,000,000 × 8 = 200,000,000 bits, and 200,000,000 ÷ 1.6 = 125,000,000 bits per second, or 125 Mbps.
At that speed a 50 GB game takes 50,000,000,000 × 8 ÷ 125,000,000 = 3,200 seconds to download, about 53 minutes. The download time calculator does this sum for any file size.
Key terms
- Download speed
- How fast data arrives from the internet, in megabits per second (Mbps).
- Upload speed
- How fast data leaves your device for the internet, in Mbps.
- Ping (latency)
- The round-trip time of a small message to the server and back, in milliseconds.
- Jitter
- The average variation between consecutive ping measurements.
- Loaded latency
- Ping measured while the connection is busy downloading or uploading. A big rise points to bufferbloat.
- Bufferbloat
- Extra delay caused by oversized buffers in routers and modems when the line is full.
Frequently asked questions
What is a good internet speed?
For a household, 100 Mbps download and 20 Mbps upload covers several people streaming, working and gaming at once. That is also the FCC's benchmark for fixed broadband in the United States, first set in March 2024. One person who mostly browses and streams in HD can manage with 25 Mbps.
How fast is 100 Mbps?
100 Mbps is 12.5 megabytes per second, so a 1 GB file takes about 80 seconds and a 4K film stream uses only a small part of it.
Why is my speed test lower than the speed I pay for?
Wi-Fi is the usual reason. Walls, distance and other devices on the network all cut the speed. Test again with a cable plugged into the router to see what your line really delivers, and pause downloads, cloud backups and streams on other devices first.
What is ping and what is a good ping?
Ping is the time a small message takes to reach the server and come back, in milliseconds. Under 20 ms is excellent, under 50 ms is good for online games and video calls, and above 100 ms you start to notice lag.
What is jitter?
Jitter is how much the ping changes from one moment to the next. Low jitter (under about 10 ms) keeps calls and games smooth, while high jitter causes choppy audio and rubber-banding in games even when the average ping is fine.
What is the difference between Mbps and MB/s?
Internet speeds are in megabits per second (Mbps), but file sizes and download managers usually use megabytes per second (MB/s). One byte is 8 bits, so divide Mbps by 8 to get MB/s: 80 Mbps is 10 MB/s.
Why is my upload speed much lower than my download speed?
Most cable, DSL and mobile plans are asymmetric and give far more capacity to downloads. Fibre plans are often symmetric, with the same speed both ways.
How much data does the speed test use?
Usually between 50 MB and 200 MB, depending on how fast your connection is. On a mobile plan with a small data allowance, that adds up.