Internet Speed Test

Click Start Speed Test to load an external OpenSpeedTest widget. That provider measures browser download and upload transfers and network latency. iCalculateFast embeds the test; it does not run an independent measurement service.

Downloading 10,000,000 bytes in 2 seconds corresponds to 40 Mbps. A 100 Mbps connection has a theoretical maximum of 12.5 megabytes per second before overhead.

Repeat with other traffic paused and compare Wi-Fi with a wired connection. Server distance, cache, congestion and device performance affect results.

One test is not a service guarantee. The widget requires JavaScript and access to external test servers and may fail when blocked. The provider's privacy practices apply after you start the test.

Click Start Speed Test to load the external OpenSpeedTest widget. The measurement is supplied by that provider, not by an independent iCalculateFast testing service. It requires JavaScript and access to the provider's servers. Starting the widget also means interacting with an external service whose privacy practices apply. The explanation on this page is available without running a test, but it is not itself a measurement of your connection.

Before testing, note which device and connection you are using. A laptop on Wi-Fi and a desktop connected by cable can produce different results even on the same broadband plan. Background downloads, video calls and other household traffic may affect the available capacity during the test. Record the conditions alongside the result so a later comparison is useful. One number without that context can make a device issue look like a provider issue.

Broadband speed is commonly expressed in megabits per second, written Mbps. File sizes are often expressed in megabytes, written MB, and there are eight bits in a byte. A theoretical 100 Mbps transfer therefore corresponds to 12.5 decimal megabytes per second before overhead. If a download application displays around a dozen MB per second, it is not necessarily reporting a speed eight times worse than a test that shows 100 Mbps.

A decimal 100 MB file contains 800 megabits. At a constant 100 Mbps, the ideal arithmetic transfer time is eight seconds. An actual transfer can take longer because of protocol overhead, server limits and changing conditions. Some software also uses binary size units, adding another comparison issue. The speed test does not guarantee how quickly every website or download server will deliver a particular file; it measures the test transfer under its own conditions.

Download capacity matters when data arrives at your device, such as a large file or video stream. Upload capacity matters when your device sends data, such as a file backup or outgoing video. A fast download result does not imply an equally fast upload result. Compare each measurement with the activity you are investigating rather than reducing the whole connection to whichever number is largest.

Latency concerns response delay rather than the amount of data transferred each second. A high-capacity connection can still feel slow in an interactive task if response delays are large. The provider's measured delay is not a guarantee of latency to every game, work server or website. Server location, routing and congestion can differ. This page does not diagnose those causes or assign a technical fault based on one completed test.

Repeat the test under comparable conditions and try a wired connection if practical. Check whether other devices are actively transferring data, and compare more than one time of day. These comparisons can help distinguish a recurring pattern from a single busy moment. They do not prove the cause by themselves. If you contact your provider, share the connection type, device, test time and repeated observations rather than only the highest or lowest number.

If the widget does not load, a browser extension, network policy or unavailable external service may be involved. Do not disable important security protections indiscriminately to force a result. Confirm whether the provider is accessible under your network's permitted settings. A failed widget is not a zero-speed measurement. The calculator page cannot guarantee the availability of third-party servers, certify your broadband service or replace a diagnostic investigation when the connection repeatedly performs poorly.