How the calculation works
The ideal time is file size in bits divided by connection speed in bits per second. A byte contains eight bits. Network speed is normally written in decimal units, so 100 Mbps means 100,000,000 bits per second. The selected connection condition then reduces usable throughput to produce the likely time and range.
GB and GiB are different sizes
GB is decimal: 1 GB equals 1,000,000,000 bytes. GiB is binary: 1 GiB equals 1,073,741,824 bytes. NIST lists these definitions separately, which is why this calculator never treats them as interchangeable.1
| Unit | Bytes | Meaning |
|---|---|---|
| 1 MB | 1,000,000 | Decimal megabyte |
| 1 MiB | 1,048,576 | Binary mebibyte |
| 1 GB | 1,000,000,000 | Decimal gigabyte |
| 1 GiB | 1,073,741,824 | Binary gibibyte |
Mbps is not MB/s
The lowercase b means bits; uppercase B means bytes. Divide Mbps by eight to find the ideal MB/s. A 100 Mbps connection therefore tops out at 12.5 MB/s before overhead. Upload speed can also be lower than download speed, so use the upload result from a speed test when estimating an upload.
Examples
How long does it take to upload 10 GB at 100 Mbps?
The ideal time is 13 minutes 20 seconds. With the default 80% efficiency model, the likely time is 16 minutes 40 seconds, with a range of about 15 minutes 41 seconds to 17 minutes 47 seconds.
Why does an upload take longer than the estimate?
The number you enter may be a short speed-test peak rather than sustained upload throughput. Wi-Fi interference, other devices, congestion, protocol overhead, and the receiving server can all add time. For a conservative planning estimate, choose the busy or unstable preset.
Frequently asked questions
Does this calculator measure my internet speed?
No. Enter a measured upload or download speed. The tool performs arithmetic only and does not run a network speed test.
Can I use it for local network transfers?
Yes. Enter the sustained link speed in Kbps, Mbps, or Gbps. For Wi-Fi or a busy network, use a lower efficiency preset.
Does Filekub guarantee this transfer time?
No. The result is a planning estimate. Actual time depends on both ends of the connection and the route between them.
Source
- NIST: Prefixes for binary multiples, accessed for byte, MB, MiB, GB, and GiB definitions.
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