Network Speed Units Explained: Mbps, MB/s, Gbps, and More
June 10, 2026 · 4 min read
Network Speed Units Explained: Mbps, MB/s, Gbps, and More
Your ISP advertises a "100 Mbps" connection. You start a large file download and your download manager reports 11.5 MB/s. A moment of confusion: are you getting what you paid for? Yes — you are. The units are different, and understanding why is the key to making sense of every speed test, bandwidth spec, and transfer estimate you'll ever read.
Bits vs Bytes: The Core Confusion
Network speeds are measured in bits per second. File sizes are measured in bytes. One byte = 8 bits. This single fact explains most of the apparent discrepancy between advertised speeds and observed download rates.
100 Mbps ÷ 8 = 12.5 MB/s (maximum theoretical download rate)
Real-world overhead (protocol headers, TCP acknowledgements, signal encoding) reduces this further, which is why you typically see 11–12 MB/s on a 100 Mbps connection rather than exactly 12.5.
The Units, Spelled Out
Bits per second (the networking world):
| Symbol | Name | Equivalent |
|---|---|---|
| bps | bits per second | 1 bit/s |
| Kbps | kilobits per second | 1,000 bps |
| Mbps | megabits per second | 1,000,000 bps |
| Gbps | gigabits per second | 1,000,000,000 bps |
| Tbps | terabits per second | 1,000,000,000,000 bps |
Bytes per second (the file/storage world):
| Symbol | Name | Equivalent |
|---|---|---|
| B/s | bytes per second | 8 bps |
| KB/s | kilobytes per second | 8,000 bps |
| MB/s | megabytes per second | 8,000,000 bps |
| GB/s | gigabytes per second | 8,000,000,000 bps |
The conversion formula is always:
MB/s = Mbps ÷ 8
Mbps = MB/s × 8
SI (Decimal) vs Binary Prefixes
This is the second source of confusion, especially for storage devices.
Networking uses decimal (SI) prefixes:
- 1 Mbps = 1,000,000 bits per second (exactly)
Some storage contexts use binary prefixes:
- 1 MiB (mebibyte) = 1,048,576 bytes = 2²⁰ bytes
Modern operating systems increasingly display file sizes in binary (GiB, MiB) but label them as "GB" or "MB" — which is why a "1 TB" hard drive shows as 931 GB in Windows (1,000,000,000,000 bytes ÷ 1,073,741,824 bytes/GiB).
For network speeds, you will almost never encounter binary prefixes — Mbps always means 1,000,000 bits per second.
Common Real-World Speeds
| Connection | Speed | Max Download Rate |
|---|---|---|
| Dial-up (classic) | 56 Kbps | ~7 KB/s |
| Basic DSL | 5 Mbps | ~625 KB/s |
| Standard cable | 100 Mbps | ~12.5 MB/s |
| Gigabit fiber | 1 Gbps | ~125 MB/s |
| 10 Gigabit LAN | 10 Gbps | ~1.25 GB/s |
| 5G (peak) | 4 Gbps | ~500 MB/s |
| Wi-Fi 6 (ax, peak) | 9.6 Gbps | ~1.2 GB/s |
Transfer Time Estimates
With a known speed and file size, transfer time is:
Time (seconds) = File Size (bits) ÷ Speed (bps)
Or more practically:
Time (seconds) = File Size (MB) × 8 ÷ Speed (Mbps)
Examples at 100 Mbps:
| File | Size | Transfer Time |
|---|---|---|
| MP3 song | 5 MB | 0.4 seconds |
| HD photo | 25 MB | 2 seconds |
| Software installer | 500 MB | 40 seconds |
| HD movie | 4 GB | ~5.3 minutes |
| 4K movie | 50 GB | ~67 minutes |
At gigabit speed, divide all times by 10.
Bandwidth vs Throughput vs Latency
These three terms are often conflated but measure different things:
Bandwidth — the maximum rate a connection can carry. A pipe's diameter.
Throughput — the rate data actually transfers in a given session. Affected by packet loss, TCP window size, server speed, and distance. Always ≤ bandwidth.
Latency — the round-trip delay between sending a packet and receiving an acknowledgement. Measured in milliseconds. A low-latency connection feels responsive even at modest bandwidth. High latency makes even a fast connection feel sluggish for interactive use (video calls, gaming, web browsing).
A satellite internet connection might offer 50 Mbps bandwidth with 600ms latency. A 4G mobile connection might offer 30 Mbps with 30ms latency. For most interactive use, the 4G connection feels much faster despite the lower bandwidth number.
Reading Speed Tests
Speed test sites measure throughput, not raw bandwidth. Results are affected by:
- Server distance — servers farther away introduce more latency, which limits TCP throughput
- Time of day — shared network congestion during peak hours
- Wi-Fi vs wired — half-duplex Wi-Fi collisions and interference reduce effective speed
- Your device — a slow CPU or saturated disk can be the bottleneck, not the network
For accurate results: use a wired connection, test to a nearby server, and average 3–5 runs.
Tools
Convert between any combination of bit and byte speed units — bps, Kbps, Mbps, Gbps, MB/s, GB/s, and more — with the Bandwidth Converter. It includes a reference table of real-world connection speeds and computes data transferred per hour at any rate.