Estimate how long a file transfer will take at a given connection speed.
File transfer time is the file size (converted to bits) divided by the link's bandwidth, adjusted upward for real-world protocol overhead — packet headers, acknowledgments, retransmissions, and the fact that connections rarely sustain 100% of theoretical link capacity. This calculator applies an overhead percentage on top of the ideal transfer time to give a more realistic estimate.
Transfer time with overhead
time = file_size / bandwidth × (1 + overhead%)
Real transfers include protocol overhead: TCP/IP headers on every packet, acknowledgment round-trips, occasional retransmissions of lost packets, and slow-start ramp-up at the beginning of the connection — none of which move actual file data.
10-20% is a reasonable estimate for a healthy wired connection. Congested, high-latency, or wireless links can see 30% or more overhead due to retransmissions and reduced effective window sizes.
Network bandwidth is conventionally quoted in bits per second (Mbps), while file sizes are quoted in bytes (MB). Converting file size to bits (× 8) before dividing keeps the units consistent and avoids an easy 8x error.
This calculator uses the SI decimal definition (1 MB = 1,000,000 bytes), matching how bandwidth and storage are marketed. See the Bandwidth Calculator for a version that lets you choose binary (MiB) units.