Download and Upload Time Calculator
Estimate how long a file takes to download or upload at a given connection speed, including realistic protocol overhead.
Estimate how long a file takes to transfer at a given connection speed, with real world overhead.
Transfer time
Realistic estimate
2m 21s
At the advertised speed: 2m
Connection speeds are quoted in bits per second, file sizes in bytes. The factor of eight between them is why a 100 Mbps line downloads at roughly 12 MB per second, not 100.
File size: 1.5 GB (1,500,000,000 bytes)
Speed: 100 Mbps
At the advertised speed: 2m
With 15% overhead: 2m 21s
Effective throughput: 10.63 MB per secondAbout the download and upload time calculator
The reason a download never matches the advertised speed is partly overhead and partly a unit confusion. Connection speeds are quoted in bits per second and file sizes in bytes, and there are eight bits in a byte, so a 100 Mbps line moves about 12 megabytes per second, not 100.
On top of that, protocol headers, acknowledgements and shared capacity mean real throughput lands somewhere below the advertised figure. Ten to twenty percent is a reasonable allowance.
How to use it
- 1Enter the file size and its unit.
- 2Enter your connection speed and its unit.
- 3Set an overhead allowance, or leave the default.
- 4Read both the ideal and the realistic estimate.
Questions
Why is my download slower than the calculation?
Advertised speed is a maximum, not a guarantee. The server's own upload limit, congestion, wifi quality and distance all reduce it, and often the server is the bottleneck rather than your line.
Is upload the same as download?
The arithmetic is identical, but most home connections have much lower upload speed than download. Use your actual upload figure.
Why does a megabyte count as a million bytes here?
Storage and network figures conventionally use powers of ten. Operating systems often use powers of two instead, which is why a drive sold as 1 TB shows as about 931 GB.
What overhead should I use?
Around 15 percent is a fair default for a normal connection. Use more for wifi or mobile, less for a wired connection to a fast server.