Megabits vs Megabytes: What's the Difference?
A 100 Mbps connection and a download speed of 12.5 MB/s use different units for the same data rate. There are eight bits in a byte, so divide Mbps by eight to get MB/s. Actual downloads may be slower. The examples below explain the units and how to compare them.
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The Core Distinction: Bits vs Bytes
A bit is the smallest unit of digital information, a single binary digit, either 0 or 1. A byte is a group of 8 bits. This 8:1 relationship is the source of all the confusion:
- Megabit (Mb or Mbit) = 1,000,000 bits, used for network speeds (Mbps)
- Megabyte (MB) = 1,000,000 bytes = 8,000,000 bits, used for file sizes and storage
- Divide any Mbps value by 8 to get MB/s; multiply any MB/s value by 8 to get Mbps
ISPs advertise in megabits because telecommunications has always measured bandwidth in bits (and because the number is 8× larger, which looks better in marketing). Your file manager shows megabytes because file sizes are measured in bytes.
Why 8, Not 1024?
There are two potential sources of confusion: bits vs bytes (factor of 8) and decimal vs binary prefixes (factor of 1.024 per prefix step). For data rates, the relevant conversion is always × 8:
- 1 Mbps = 1,000,000 bits/s ÷ 8 = 125,000 bytes/s = 0.125 MB/s
- 1 MB/s = 1,000,000 bytes/s × 8 = 8,000,000 bits/s = 8 Mbps
Internet speeds use SI decimal prefixes (1 Mbps = exactly 1,000,000 bps). The binary prefix debate (MB vs MiB) only affects storage reporting, not network speed conversions.
ISP Speed Plan → Maximum Download Speed
Divide the advertised Mbps by 8 to get the theoretical maximum download speed in MB/s. Actual speeds are typically 5–15% lower due to TCP/IP overhead and network conditions.
| ISP Plan (Mbps) | Max Download (MB/s) | 1 GB file takes |
|---|---|---|
| 10 Mbps | 1.25 MB/s | ≈ 13.3 min |
| 25 Mbps | 3.125 MB/s | ≈ 5.3 min |
| 50 Mbps | 6.25 MB/s | ≈ 2.7 min |
| 100 Mbps | 12.5 MB/s | ≈ 1.3 min |
| 200 Mbps | 25 MB/s | ≈ 40 s |
| 500 Mbps | 62.5 MB/s | ≈ 16 s |
| 1000 Mbps | 125 MB/s | ≈ 8 s |
| 2500 Mbps | 312.5 MB/s | ≈ 3 s |
| 5000 Mbps | 625 MB/s | ≈ 2 s |
| 10000 Mbps | 1250 MB/s | ≈ 1 s |
Three More Confusing Scenarios
Hard Drive "Missing" Space
You buy a '1 TB' hard drive but Windows shows 931 GB. Hard drive makers use SI: 1 TB = 1,000,000,000,000 bytes. Windows historically reports in binary gibibytes (1 GiB = 1,073,741,824 bytes). 1,000,000,000,000 ÷ 1,073,741,824 = 931 GiB. Nothing is missing.
USB 3.0 Spec vs Real Speed
USB 3.0 is rated at 5 Gbps. Dividing by 8 = 625 MB/s theoretical maximum. In practice, protocol overhead reduces this to around 400–450 MB/s for real file copies, which matches benchmark results you see online.
Wi-Fi 6 802.11ax '1200 Mbps' Claims
That 1200 Mbps is an aggregate: two radios combined (2.4 GHz + 5 GHz). Per radio, peak throughput for a single device is 600 Mbps ÷ 8 = 75 MB/s, and that's under ideal lab conditions with no other traffic.
Frequently Asked Questions
How many megabytes per second is 100 Mbps?
100 Mbps ÷ 8 = 12.5 MB/s. A 100 Mbps internet connection downloads files at a maximum of 12.5 megabytes per second under ideal conditions.
Why does my 1 Gbps internet plan only download at ~125 MB/s?
Because 1 Gbps = 1,000 Mbps = 1,000,000,000 bits per second. Dividing by 8 gives 125,000,000 bytes per second = 125 MB/s. This is the theoretical maximum; real-world speeds are slightly lower due to protocol overhead.
Is Mbps or MB/s faster?
Mbps and MB/s measure the same thing (data rate) in different units. 1 MB/s = 8 Mbps, so MB/s gives a numerically smaller but equivalent value. A connection of 8 Mbps equals exactly 1 MB/s.
Why do ISPs use Mbps instead of MB/s?
Historically, telecommunications has always measured bandwidth in bits, not bytes. Using Mbps also produces larger numbers (e.g. 100 Mbps vs 12.5 MB/s), which looks more impressive in marketing.
What is the difference between MB and MiB?
MB (megabyte) uses the SI decimal definition: 1 MB = 1,000,000 bytes. MiB (mebibyte) uses the binary definition: 1 MiB = 1,048,576 bytes (2²⁰). Hard drive manufacturers use MB; operating systems like Windows have historically used MiB while labelling them MB, causing the apparent 'missing space' discrepancy.