How long does it take to download 1 GB?
At 100 Mbps, a 1 GB file takes 80 seconds (1 min 20 s) at best; at 25 Mbps it takes 5 min 20 s, and at 1 Gbps about 8 seconds. The rule is simple: 1 GB is 8,000 megabits, so divide 8,000 by your speed in Mbps to get seconds.
The formula
A gigabyte is 1,000 megabytes and each byte is 8 bits, so 1 GB = 8,000 megabits. Time is size divided by speed:
seconds = 8,000 ÷ Mbps 1 GB at 100 Mbps = 8,000 ÷ 100 = 80 s
If your download app shows MB/s, you can skip the factor of 8: 1 GB is 1,000 MB, so at 12.5 MB/s it takes 1,000 ÷ 12.5 = 80 s. The Mbps to MB/s converter translates between the two.
1 GB download times at common speeds
| Speed | Same in MB/s | Seconds | Best case | At 90% efficiency |
|---|---|---|---|---|
| 10 Mbps | 1.25 MB/s | 800 | 13 min 20 s | 14 min 49 s |
| 25 Mbps | 3.125 MB/s | 320 | 5 min 20 s | 5 min 56 s |
| 50 Mbps | 6.25 MB/s | 160 | 2 min 40 s | 2 min 58 s |
| 100 Mbps | 12.5 MB/s | 80 | 1 min 20 s | 1 min 29 s |
| 200 Mbps | 25 MB/s | 40 | 40 s | 44.4 s |
| 300 Mbps | 37.5 MB/s | 26.7 | 26.7 s | 29.6 s |
| 500 Mbps | 62.5 MB/s | 16 | 16 s | 17.8 s |
| 1,000 Mbps (1 Gbps) | 125 MB/s | 8 | 8 s | 8.9 s |
| 2,000 Mbps (2 Gbps) | 250 MB/s | 4 | 4 s | 4.4 s |
"Best case" uses the full plan speed. The last column assumes 90% of it is usable, the value the download time calculator applies when you switch on its real-world efficiency option. For any other file size or speed, that calculator gives the exact figure.
Why real downloads take longer
- Protocol overhead. Packet headers and framing use part of every link. On gigabit Ethernet a speed test typically tops out around 940 Mbps, so 1 GB takes about 8.5 s rather than 8.
- Wi-Fi. Distance, walls and older routers or devices can cut the speed a lot, especially on faster plans.
- The server. A download is only as fast as the server sending it. Busy or distant servers, and services that limit each download, set a ceiling your plan cannot lift.
- Sharing. Other people streaming, updating or backing up take part of the line.
- Start-up time. On fast connections, a download spends a noticeable share of a few seconds getting up to speed, so small files rarely reach the full rate.
If downloads are consistently far slower than the table, run a wired speed test and compare it with your plan in the speed test checker.
GB or GiB? Check the size
Some software lists sizes in binary units while still writing "GB". A binary gigabyte (GiB) is 1,073,741,824 bytes, 7.4% more than a decimal gigabyte, so it takes 7.4% longer: about 85.9 seconds at 100 Mbps instead of 80. For quick estimates the difference hardly matters; for precise ones, check which unit the size uses. Bits vs bytes explains the two systems.
What 1 GB is in streaming terms
A gigabyte is also a useful yardstick for streaming. At Netflix's recommended 5 Mbps for 1080p, a stream uses up to 2.25 GB an hour, so 1 GB lasts at least about 26 min 40 s. At YouTube's 20 Mbps for 4K, 1 GB lasts at least 6 min 40 s. Real streams often use less than the recommendation, so these are minimum viewing times per gigabyte.
Larger files scale in a straight line: 10 GB takes ten times as long. How long to download 10 GB has that table, with advice for big game and video downloads.
Key takeaways
- 1 GB = 8,000 megabits, so seconds = 8,000 ÷ Mbps.
- 1 GB takes 80 s at 100 Mbps, 5 min 20 s at 25 Mbps and 8 s at 1 Gbps.
- Allow about 10% extra for overhead; Wi-Fi and the server can add much more.
- A 1 GiB file is 7.4% larger than 1 GB and takes 7.4% longer.
Frequently asked questions
How long does 1 GB take at 50 Mbps?
160 seconds (2 min 40 s) at the full speed, or about 2 min 58 s at 90% efficiency.
How many GB can I download in an hour at 100 Mbps?
Up to 45 GB: 100 Mbps × 3,600 s = 360,000 megabits, divided by 8,000 megabits per GB.