Why Mbps and GB aren't directly comparable
Mbps (megabits per second) measures internet speed. GB (gigabytes) measures an amount of data. A bit and a byte aren't the same unit — there are 8 bits in a byte — so converting between them always means dividing by 8 first, then multiplying by however long the transfer runs.
Step 1 — bits to bytes: MB per second = Mbps ÷ 8 Step 2 — rate to total: Total MB = (MB per second) × seconds elapsed Example: 100 Mbps for one hour 100 ÷ 8 = 12.5 MB per second 12.5 × 3,600 seconds = 45,000 MB = 45 GB Data transferred by common speed and time period
| Speed | Per second | Per hour | Per month (30 days, 24/7) |
|---|---|---|---|
| 25 Mbps | 3.13 MB | 11.25 GB | 8.10 TB |
| 50 Mbps | 6.25 MB | 22.50 GB | 16.20 TB |
| 100 Mbps | 12.50 MB | 45.00 GB | 32.40 TB |
| 300 Mbps | 37.50 MB | 135.00 GB | 97.20 TB |
| 1,000 Mbps (1 Gbps) | 125.00 MB | 450.00 GB | 324.00 TB |
The monthly figures assume the connection runs at full speed continuously, 24 hours a day — a theoretical ceiling, not a realistic usage estimate. Real-world usage is almost always far lower, since a connection sits idle most of the time even for heavy users.
GB vs. GiB — a second, separate unit trap
Even after the bits-to-bytes step, "gigabyte" itself has two competing definitions. GB (decimal) counts 1,000 megabytes to a gigabyte — this is what internet providers and storage manufacturers use in marketing and data caps. GiB (binary) counts 1,024 — this is closer to what your operating system often reports for file and drive sizes. The two differ by about 7%, which is why a "1 TB" hard drive shows up as roughly 931 GiB in Windows.
Decimal (GB): 45,000,000,000 bytes ÷ 1,000³ = 45.00 GB Binary (GiB): 45,000,000,000 bytes ÷ 1,024³ = 41.91 GiB Neither figure is "wrong" — they're answering the question with two different rulers. This calculator defaults to GB (matching how your ISP or data cap is described) and lets you switch to GiB if you're comparing against a file size your computer reported.
Frequently asked questions
How many GB is 1000 Mbps?
A 1000 Mbps (1 Gbps) connection can transfer up to 125 MB per second, 450 GB per hour, or a theoretical maximum of about 324 TB per month if it ran at full speed continuously. Actual usage is normally far below this ceiling.
Why does my 100 Mbps connection only show 12.5 MB/s?
Internet speed is advertised in megabits (Mbps), but download managers and browsers typically show megabytes (MB/s). There are 8 bits in a byte, so 100 Mbps divided by 8 is exactly 12.5 MB/s — the connection isn't underperforming, the two figures are just measured in different units.
How much data does 100 Mbps use per hour?
At full speed, a 100 Mbps connection transfers up to 45 GB per hour. That's a ceiling based on continuous full-speed use, not what a typical hour of browsing or streaming actually consumes.
What's the difference between Mbps and MBps?
The lowercase "b" in Mbps means bits; the uppercase "B" in MBps means bytes. They look similar but differ by a factor of 8 — 100 Mbps equals 12.5 MBps, not 100 MBps. Internet speeds are almost always quoted in Mbps; file sizes and download managers almost always use MB or MBps.