How to calculate download time
Internet speeds are quoted in megabits per second (Mbps), while file sizes are in megabytes (MB). There are 8 bits in a byte, so convert the file size to bits first. Real transfers also lose about 5–15% to TCP/IP overhead and Wi-Fi.
Time (s) = File size (MB) × 8 ÷ (Speed (Mbps) × (1 − overhead))
Monthly GB = Visitors × Pages × Page MB × Safety ÷ 1000
Example: 50 GB game on 300 Mbps
50 GB × 8 = 400,000 Mb. At 300 Mbps with 10% overhead (270 Mbps usable): 400,000 ÷ 270 = 1,481 s, about 25 minutes.
Time to download 1 GB
| Speed | 1 GB | 10 GB | 100 GB |
|---|---|---|---|
| 25 Mbps | 5 min 20 s | 53 min | 8 h 53 min |
| 100 Mbps | 1 min 20 s | 13 min | 2 h 13 min |
| 300 Mbps | 27 s | 4 min 27 s | 44 min |
| 1 Gbps | 8 s | 1 min 20 s | 13 min |
Theoretical times, no overhead.
Frequently asked questions
What is the difference between Mbps and MB/s?
Mbps is megabits per second; MB/s is megabytes per second. Divide Mbps by 8 to get MB/s: 300 Mbps ≈ 37.5 MB/s.
Why is my download slower than my plan speed?
Protocol overhead, Wi-Fi interference, server limits and network congestion all reduce real throughput.
How much bandwidth does a website need?
A site with 50,000 visitors a month viewing 3 pages of 2.5 MB uses about 375 GB, or roughly 560 GB with a 1.5× safety factor.