Transfer Time
This free data transfer time calculator estimates download or upload time from a file size and connection speed, correctly converting between bytes (file size) and bits (connection speed). Nothing you enter is sent anywhere or stored.
How to Use It
- Enter the file size and select its unit (KB, MB, GB, or TB).
- Enter the connection speed and select its unit (Kbps, Mbps, or Gbps).
- The estimated transfer time updates instantly, no submit button.
How It Works
This calculator converts the file size from bytes to bits (multiplying by 8, since one byte is 8 bits), then divides by the connection speed in bits per second to get the transfer time in seconds. That raw seconds figure is then broken into the two most meaningful time units (hours and minutes, or minutes and seconds, for example) rather than shown as an unreadable decimal.
Formula
transfer time (seconds) = (file size in bytes × 8) ÷ connection speed (bits per second)
A worked example: a 500 MB file (500 × 1,000,000 bytes) on a 100 Mbps connection (100 × 1,000,000 bits per second) takes 40 seconds at full speed. A much larger 25 GB file on a more modest 50 Mbps connection takes 4,000 seconds, about 1 hour and 6 minutes, since both the file is 50 times larger and the connection is half the speed.
Everything runs client-side in your browser. Nothing you enter is sent anywhere or stored.
Frequently Asked Questions
Why doesn't a "100 Mbps" connection transfer 100 megabytes per second?
Connection speeds are almost universally advertised in bits per second, while file sizes are measured in bytes, and one byte is 8 bits. A 100 Mbps connection transfers about 12.5 megabytes per second (100 divided by 8), not 100 megabytes per second. Mixing up bits and bytes is one of the most common sources of confusion when estimating download or upload time.
Why does a real transfer usually take longer than this estimate?
This calculator assumes the full rated connection speed is available for the entire transfer, which real transfers rarely achieve. Network overhead, other devices sharing the same connection, and the sending server's own upload speed (which may be slower than your download speed) all commonly slow a real transfer below the theoretical estimate.
Why does my computer show a slightly different file size than I expected?
This calculator uses decimal file size units (1 KB equals 1,000 bytes, 1 MB equals 1,000,000 bytes), matching how file sizes are most commonly displayed and how storage manufacturers label capacity. Some operating systems instead calculate "MB" and "GB" using binary, 1,024-based units internally, which reports a slightly smaller number for the same actual file, a long-standing inconsistency in how computers describe file sizes.
Does a faster connection always mean a faster download?
Only up to the speed of the slowest link in the chain. If the server you're downloading from can only upload at 20 Mbps, having a 500 Mbps home connection doesn't make the transfer any faster, the download is limited by whichever end of the connection is slowest.
Can you give a real-world example?
A 500 MB file on a 100 Mbps connection takes about 40 seconds at full speed. A 25 GB file (a fairly large game or video file) on a more modest 50 Mbps connection takes about 1 hour and 6 minutes, a useful reminder of how much longer large files take on typical home connections.