Downloads
How long does 15 GB take to download at 10 Mbps?
3 h 31 min
to download 15 GB at 10 Mbps, best case. Typical: 4 h 10 min (at 80 % efficiency, our estimate for Wi-Fi and busy servers).
10 Mbps is slow rural broadband or weak mobile signal. Large downloads take hours, so it is worth knowing the number before you start one.
The arithmetic
- 15 GB × 8 bits per byte = 120 gigabits (120,000,000,000 bits)
- 10 Mbps = 10,000,000 bits per second = 1.25 MB/s at most
- 120,000,000,000 ÷ 10,000,000 = 12,000 s = 3 h 20 min with zero overhead
- TCP/IP and Ethernet framing use about 5 % of the line (1,460 data bytes per 1,538 on the wire): 12,000 ÷ 0.949 = 3 h 31 min
If the size is really 15 GiB (some stores and Windows label GiB as GB), it is 7.4 % bigger: 3 h 46 min best case.
| Speed | Best case (95 %) | Typical (80 %, estimate) |
|---|---|---|
| 10 Mbps | 3 h 31 min | 4 h 10 min |
| 25 Mbps | 1 h 24 min | 1 h 40 min |
| 50 Mbps | 42 min 8 s | 50 min |
| 100 Mbps | 21 min 4 s | 25 min |
| 300 Mbps | 7 min 1 s | 8 min 20 s |
| 500 Mbps | 4 min 13 s | 5 min |
| 1,000 Mbps | 2 min 6 s | 2 min 30 s |
Sources and assumptions
- Overhead: 94.9 % efficiency from TCP/IPv4 on 1,500-byte Ethernet frames (computed); 80 % 'typical' is our estimate.