Bits per second or bytes per second
A data rate tells how much information passes through a link each second. Network gear, internet providers and speed tests count in bits per second, written with a lowercase b: kbps, Mbps, Gbps. Browsers, download clients and storage devices count in bytes per second, with a capital B: kB/s, MB/s, GB/s. Since a byte has 8 bits, the same connection shows a number eight times smaller in bytes, which explains most surprises about download speed.
How to use this converter
Type a speed in any field and every other unit updates as you type. Enter the speed of your internet plan to see the fastest download you can expect, or enter the speed shown by a download to check what your connection really delivers. Common pairs below each have their own page with the formula, an example and a chart.
Key equivalents
- 1 byte per second = 8 bits per second
- 1 Mbps = 1,000 kbps = 0.125 MB/s
- 8 Mbps = 1 MB/s
- 1 Gbps = 1,000 Mbps = 125 MB/s
- 1 GB/s = 8 Gbps
Estimating a download time
Convert the plan speed to MB/s, then divide the file size by that speed. A 100 Mbps connection moves 12.5 MB/s, so a 1 GB file (1,000 MB) takes about 80 seconds. Real downloads are usually 5 to 10% slower than this ideal, because of protocol overhead, Wi-Fi quality and the speed of the server. Upload speeds are often much lower than download speeds on cable and DSL lines, so check both numbers if you send large files or back up to the cloud.
Decimal prefixes
Data rates use decimal prefixes: one megabit per second is exactly 1,000,000 bits per second, not 1,048,576. Some download tools nevertheless show speeds in binary MiB/s while labeling them MB/s, which makes them read about 5% lower. For storage sizes and the difference between MB and MiB, see the data storage converter.
Data rate units compared
| Unit | Symbol | In bits per second |
|---|---|---|
| Bit per second | bps | 1 |
| Kilobit per second | kbps | 1,000 |
| Megabit per second | Mbps | 1,000,000 |
| Gigabit per second | Gbps | 1,000,000,000 |
| Byte per second | B/s | 8 |
| Kilobyte per second | kB/s | 8,000 |
| Megabyte per second | MB/s | 8,000,000 |
| Gigabyte per second | GB/s | 8,000,000,000 |
The units in detail
What is one bit per second?
The bit per second is the base unit of data transmission speed. On its own it is tiny; serial ports, sensors and old modems are counted in thousands of bits per second, and modern links in millions or billions.
What is one kilobit per second?
The kilobit per second is 1,000 bits per second. Audio bitrates use it: an MP3 at 128 kbps or a music stream at 320 kbps. Dial-up modems topped out at 56 kbps.
What is one megabit per second?
The megabit per second, one million bits per second, is the unit of internet plans, Wi-Fi speed tests and video bitrates. HD streaming needs about 5 Mbps and 4K about 15 to 25 Mbps per stream.
What is one gigabit per second?
The gigabit per second equals 1,000 Mbps. It rates fiber plans, Ethernet ports and USB links: gigabit Ethernet carries 1 Gbps, USB 3.2 Gen 2 carries 10 Gbps.
What is one byte per second?
The byte per second, 8 bits per second, measures how fast files move. Download managers, browsers and disk benchmarks show speeds in bytes per second and its multiples, which is why they read eight times lower than a speed test.
What is one kilobyte per second?
The kilobyte per second is 1,000 bytes, or 8,000 bits, per second. Slow mobile connections and throttled downloads are often reported in kB/s.
What is one megabyte per second?
The megabyte per second is one million bytes, or 8 megabits, per second. Download clients, game launchers and SD cards use it: a card rated 90 MB/s writes 4K video comfortably.
What is one gigabyte per second?
The gigabyte per second is 8 gigabits per second. It describes fast storage: a SATA SSD reads around 0.55 GB/s, and an NVMe PCIe 4.0 SSD up to about 7 GB/s.