Mbps vs. MB/s: What's the Difference?

Bits and bytes are different units

A bit is one binary digit. A byte contains eight bits. Lowercase b usually means bits; uppercase B means bytes. That is why 100 Mbps and 100 MB/s are not the same speed.

Mbps means megabits per second. MB/s means megabytes per second. For decimal network units, divide Mbps by eight to estimate MB/s, or multiply MB/s by eight to estimate Mbps. Gbps means gigabits per second; 1 Gbps is 1,000 Mbps, ideally 125 MB/s.

Worked conversions

The time column assumes a 1 GB file equals 1,000 MB and ignores all overhead. A download manager might use binary units such as MiB/s instead; those numbers will differ slightly even when the underlying byte rate is the same.

Why the labels differ

Network connection rates are conventionally described in bits per second, so an internet plan often shows Mbps. Files are commonly described in bytes, so a browser or download app often shows MB/s. Neither label alone tells you how fast a particular file will arrive. A 100 Mbps link has a theoretical ceiling near 12.5 MB/s before overhead, not 100 MB/s.

Why actual downloads are slower

The simple division is a ceiling based on the stated link rate. Protocol overhead consumes some capacity. Wi-Fi interference, weak signal, older equipment, shared-network congestion, your device, the remote server, and limits on a single connection can reduce the observed rate. A plan may also describe a maximum or advertised rate rather than a guarantee for each download.

If a 1 GB transfer on a 100 Mbps plan takes two minutes instead of 80 seconds, that does not by itself identify the bottleneck. Check whether the speed shown is Mbps or MB/s, whether the file size is GB or GiB, and whether the device is using Wi-Fi or a wired link before comparing numbers.

Use the right tool for the question

Convert between rate units when a plan and an app use different labels. Estimate time when you know both file size and connection speed. Convert file units when a download size is shown in MB, GB, or TB. These tools use clear decimal assumptions; real transfers can differ.