Uploads and backup
How long does it take to back up 1 TB to the cloud at 20 Mbps upload?
4 days 21 h
to upload 1 TB at 20 Mbps, best case. Typical: 5 days 19 h (at 80 % efficiency, our estimate for Wi-Fi and busy servers).
Most home connections upload far more slowly than they download, so the first full backup to a cloud service (the seed) takes days, not hours. After that only changes are sent.
Uploading only overnight, 8 hours a night, it takes about 15 nights.
The arithmetic
- 1,000 GB × 8 bits per byte = 8,000 gigabits (8,000,000,000,000 bits)
- 20 Mbps = 20,000,000 bits per second = 2.5 MB/s at most
- 8,000,000,000,000 ÷ 20,000,000 = 400,000 s = 4 days 15 h with zero overhead
- TCP/IP and Ethernet framing use about 5 % of the line (1,460 data bytes per 1,538 on the wire): 400,000 ÷ 0.949 = 4 days 21 h
If the size is really 1,000 GiB (some stores and Windows label GiB as GB), it is 7.4 % bigger: 5 days 6 h best case.
| Speed | Best case (95 %) | Typical (80 %, estimate) |
|---|---|---|
| 10 Mbps | 9 days 18 h | 11 days 14 h |
| 25 Mbps | 3 days 22 h | 4 days 15 h |
| 50 Mbps | 46 h 49 min | 2 days 8 h |
| 100 Mbps | 23 h 25 min | 27 h 47 min |
| 300 Mbps | 7 h 48 min | 9 h 16 min |
| 500 Mbps | 4 h 41 min | 5 h 33 min |
| 1,000 Mbps | 2 h 20 min | 2 h 47 min |
Sources and assumptions
- Overhead: 94.9 % efficiency from TCP/IPv4 on 1,500-byte Ethernet frames (computed); 80 % 'typical' is our estimate.