Transfer Time Calculator

File transfer time depends on two factors: the size of the file (measured in bytes) and the speed of your connection (measured in bits per second). The critical detail most people miss is the distinction between bits and bytes — there are 8 bits in every byte. When your ISP advertises a 100 Mbps connection, that translates to a theoretical maximum of 12.5 megabytes per second. In practice, protocol overhead, network congestion, and hardware limitations reduce this further. A typical TCP/IP connection loses 5–15% of its bandwidth to packet headers, acknowledgments, error correction, and TLS encryption. That is why a 100 Mbps connection often delivers only 10–11 MB/s in real-world file transfers rather than the theoretical 12.5 MB/s. This calculator accounts for that overhead and lets you adjust it based on your specific conditions.

The fundamental formula is: Transfer Time = File Size (bits) ÷ Effective Speed (bits/sec). Confusion arises because file sizes use bytes (KB, MB, GB, TB) while network speeds use bits (Kbps, Mbps, Gbps). To convert, multiply the file size in bytes by 8 to get bits. Additionally, storage manufacturers use decimal prefixes (1 GB = 1,000,000,000 bytes) while some operating systems use binary prefixes (1 GiB = 1,073,741,824 bytes). This calculator uses the standard decimal (SI) convention, which matches what ISPs and hardware manufacturers advertise. For USB and local transfers, the rated speed is the theoretical maximum — actual throughput depends on the slowest device in the chain (often the hard drive), cable quality, and whether the bus is shared with other peripherals. Wi-Fi real-world speeds are typically 30–60% of the rated maximum due to signal degradation, interference, and shared airtime.