Calculate file transfer times, required bandwidth, and data throughput for various connection speeds.
This tool works the size/speed/time relationship for file transfers in either direction: give it a file size and a connection speed to get a transfer time, or give it a file size and a target time to get the minimum bandwidth required. It converts every input to a common bits-per-second basis before doing the division. The detail that trips people up most is byte-versus-bit: connection speeds are quoted in megabits per second (Mbps) while file sizes are usually shown in megabytes (MB), an 8x difference that silently skews the answer if you read one column as the other.
A concrete input and expected output from the current implementation.
Input
File size: 1 GB, Connection speed: 100 Mbps
Expected output
Transfer time: 80 seconds (1 minute 20 seconds)
1 GB = 8,000,000,000 bits; at 100 Mbps (100,000,000 bits per second), 8,000,000,000 / 100,000,000 = 80 seconds, assuming decimal GB and the full nominal speed with no protocol overhead.
Before any division happens, the tool converts both inputs to a single unit, typically bits: file size moves from bytes/kilobytes/megabytes/gigabytes into bits, and connection speed moves from its stated unit (Kbps, Mbps, Gbps) into bits per second. This is where decimal (1000-based) versus binary (1024-based) prefix choices matter, since they shift the converted value by several percent either way.
The underlying relationship is size = speed x time, so given any two of the three the tool computes the third: file size plus connection speed yields transfer time; file size plus a target time yields the minimum bandwidth needed; file size plus an observed time yields actual throughput. It then converts that result back into readable units like seconds, minutes, or hours.
The calculation is theoretical: it assumes the full nominal connection speed is available and dedicated to that one transfer for the whole duration. Real transfers lose throughput to protocol overhead, network congestion, other devices on the connection, and the usual gap between advertised and actual ISP speeds, so the real transfer is almost always slower than the calculated number.
That distinction is exactly what makes the math correct, but I can't confirm from here which unit options this specific tool's dropdowns expose. Check the unit selectors before relying on the result for a hard deadline; if only plain 'GB' and 'Mbps' labels are shown, assume decimal (1000-based) prefixes rather than binary (1024-based) ones.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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