Downloads
How long does a 4 GB movie take to download at 25 Mbps?
22 min 28 s
to download 4 GB at 25 Mbps, best case. Typical: 26 min 40 s (at 80 % efficiency, our estimate for Wi-Fi and busy servers).
4 GB is roughly a two-hour film in good HD. 25 Mbps is a common entry broadband speed, and also roughly what a decent 4G connection manages.
The arithmetic
- 4 GB × 8 bits per byte = 32 gigabits (32,000,000,000 bits)
- 25 Mbps = 25,000,000 bits per second = 3.12 MB/s at most
- 32,000,000,000 ÷ 25,000,000 = 1,280 s = 21 min 20 s with zero overhead
- TCP/IP and Ethernet framing use about 5 % of the line (1,460 data bytes per 1,538 on the wire): 1,280 ÷ 0.949 = 22 min 28 s
If the size is really 4 GiB (some stores and Windows label GiB as GB), it is 7.4 % bigger: 24 min 8 s best case.
| Speed | Best case (95 %) | Typical (80 %, estimate) |
|---|---|---|
| 10 Mbps | 56 min 11 s | 1 h 7 min |
| 25 Mbps | 22 min 28 s | 26 min 40 s |
| 50 Mbps | 11 min 14 s | 13 min 20 s |
| 100 Mbps | 5 min 37 s | 6 min 40 s |
| 300 Mbps | 1 min 52 s | 2 min 13 s |
| 500 Mbps | 1 min 7 s | 1 min 20 s |
| 1,000 Mbps | 34 s | 40 s |
Sources and assumptions
- Overhead: 94.9 % efficiency from TCP/IPv4 on 1,500-byte Ethernet frames (computed); 80 % 'typical' is our estimate.