Data Transfer Time Calculator
Transfer time is governed by one relationship: file size in bits divided by the connection speed in bits per second. The catch is that file sizes are usually in megabytes and speeds in megabits, an eight-to-one difference, and that real transfers never hit the rated line speed. Enter the file size in megabytes, the connection speed in megabits per second, and an efficiency factor for overhead. This calculator returns the estimated transfer time in seconds, minutes, and a readable hours-minutes-seconds breakdown.
Transfer time formula
file bits = file MB * 8 (megabits)
effective speed = speed Mbps * efficiency
seconds = file megabits / effective speed
effective MB/s = effective speed / 8
The factor of 8 converts megabytes to megabits. The efficiency factor accounts for protocol overhead and real-world losses; 1.0 is the theoretical best case.
Transfer time examples (at 90 percent efficiency)
- 1 GB (1,000 MB) over 100 Mbps: about 88.9 seconds.
- 1 GB over 1,000 Mbps (gigabit): about 8.9 seconds.
- 100 MB over 50 Mbps: about 17.8 seconds.
- 10 GB over 100 Mbps: about 14.8 minutes.
- Halve the efficiency and the time roughly doubles.
Transfer time: frequently asked questions
How do I calculate file transfer time?
Convert the file size to bits, then divide by the speed in bits per second. A byte is 8 bits, so a 100 megabyte file is 800 megabits. At 100 megabits per second that is 8 seconds at the theoretical maximum. Real transfers run slower because of protocol overhead, so divide by an efficiency factor.
Why are megabytes and megabits different?
File sizes are usually quoted in megabytes (MB) while connection speeds are quoted in megabits per second (Mbps). One byte is 8 bits, so a connection rated at 100 Mbps moves at most 12.5 MB per second. Mixing the two up is the most common reason transfer estimates look eight times too fast or slow.
What efficiency factor should I use?
Real throughput is below the line rate because of TCP/IP overhead, latency, and congestion. A common rule of thumb is 80 to 95 percent of the rated speed on a clean wired link, lower over Wi-Fi or busy networks. The efficiency factor is a user-editable input so you can match your own measurements.
Does this work for uploads too?
Yes. Enter your upload speed instead of your download speed. Many connections are asymmetric, with upload much slower than download, so use the correct figure for the direction of transfer.
Sources and definitions
- Transfer time is file size divided by data rate, with 1 byte = 8 bits. These are standard digital information definitions.
- National Institute of Standards and Technology: SI prefixes (mega = 10 to the 6th).
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.