The data transfer formula
Data sizes are in bytes and bandwidth is in bits per second, so you convert the size to bits (×8) and divide by the bandwidth:
seconds = ( size MB × 8 ) ÷ bandwidth Mbps
The calculator first normalises everything: GB and TB become MB (×1000 and ×1,000,000), and Gbps becomes Mbps (×1000). Then it divides and expresses the answer in seconds, minutes and hours so large transfers are easy to read.
Worked example
A 50 GB backup over a 1 Gbps link:
Normalise: 50 GB = 50,000 MB; 1 Gbps = 1000 Mbps.
Bits: 50,000 × 8 = 400,000 megabits.
Time: 400,000 ÷ 1000 = 400 s ≈ 6.7 min.
Bandwidth ≠ throughput: the link's rated capacity is a ceiling. Real transfers lose time to latency, retransmits and disk speed, so add roughly 15% for a realistic figure.
Scaling to large transfers
The same formula scales from a few megabytes to terabytes. Doubling the data doubles the time; doubling the bandwidth halves it. For very large migrations, remember that the source disk, the destination and any encryption can become the real bottleneck long before the network does.