Result
This page has no server side at all. The table you paste is parsed by JavaScript inside your own browser, the chart is drawn on a canvas element on your machine, and the export file is assembled locally. Nothing is uploaded, stored or written to any log. You can disconnect from the network after the page has loaded and everything will still work — which is the simplest way to verify the claim yourself.
Facts and limits of this method
| File size | Binary system: 1 KB = 1024 bytes, matching what the operating system shows |
|---|---|
| Speed in bits per second | Decimal system: 1 Kbps = 1000 bits/s, matching what ISPs advertise |
| Mbps and MB/s are different units | MB/s is 8 times larger than Mbps at the same number (1 byte = 8 bits) |
| Formula | Time = file size in bytes ÷ speed in bytes per second |
When it misleads you
- ISPs almost always advertise speed in megabits per second (Mbps), while the operating system shows file size in megabytes (MB) — these are different units, off by a factor of 8, and mixing them up is the single most common source of an 8x error in this kind of calculation. Double-check you picked the right speed unit.
- The calculation assumes the entire advertised connection speed is used exclusively for this one file, with no other devices on the network and no protocol overhead — in practice, actual throughput is almost always lower than the advertised speed.
- File size units (KB, MB, GB, TB) use the binary definition (powers of 1024), matching what Windows Explorer or macOS Finder shows, but different from the decimal definition (powers of 1000) that storage device manufacturers sometimes use on packaging.
- The result doesn't account for connection setup time, DNS resolution, server response time, or possible interruptions and retries — it's the pure data-transfer time at a constant advertised speed.
How it is calculated
The file size is converted to bytes using the binary system: 1 KB = 1024 bytes, 1 MB = 1024² bytes, 1 GB = 1024³ bytes, 1 TB = 1024⁴ bytes.
The speed is converted to bytes per second. Bit-based units (Kbps, Mbps, Gbps) are divided by 8 to get bytes, since one byte equals 8 bits. Byte-based units (KB/s, MB/s) are used as-is, with just a decimal multiplier of 1000.
The download time in seconds is the file size in bytes divided by the speed in bytes per second.
The result in seconds is formatted into a readable form: days, hours, minutes and seconds, showing only the units needed for that particular duration.
Questions and answers
Why do MB/s and Mbps give different times for the same number?
They're different units: one byte equals 8 bits, so a speed of 100 MB/s is 8 times faster than 100 Mbps. ISPs almost always advertise speed in bits (Mbps), while file size is in bytes (MB).
Why is the actual download time longer than the calculated one?
The calculation assumes ideal conditions — the entire advertised connection speed with no other devices on the network and no losses to protocol overhead. In reality, actual throughput is usually lower than advertised.
Which speed unit should I pick if my ISP advertises "100 Mbps"?
Pick "Mbps" — that's the standard unit internet providers use to state their plan speed.
Is my data sent anywhere?
No, the whole calculation runs in your browser.