File Transfer Time Calculator
Estimate how long a file transfer will take given file size, link bandwidth, and protocol overhead.
Inputs
Accounts for headers, retransmits, ACKs, and imperfect link utilization
Estimated Transfer Time
44 seconds
Transfer Time
44.00s
Ideal (No Overhead) Time
40.00s
Effective Throughput
90.909Mbps
Step by step
Values used
File Size = 500 MB; Link Bandwidth = 100 Mbps; Protocol Overhead = 10 %
Transfer time with overhead
time = file_size / bandwidth × (1 + overhead%)
Estimated Transfer Time
= 44 seconds
Transfer Time
= 44.00 s
Ideal (No Overhead) Time
= 40.00 s
Effective Throughput
= 90.909 Mbps
How it works
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.
Formula
Transfer time with overhead
time = file_size / bandwidth × (1 + overhead%)
- S
- File size in bits
- B
- Bandwidth in bits per second
- o
- Overhead percentage
Frequently Asked Questions
Why does the transfer take longer than the theoretical minimum?
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.
What overhead percentage should I use?
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.
Why convert MB to bits instead of just dividing by MBps?
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.
Does this use decimal (SI) or binary (IEC) megabytes?
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.