Data Transfer Calculator

Mbps (megabits per second) and MBps (megabytes per second) are often confused but differ by a factor of 8. Network speeds are almost always advertised in Mbps (bits), while file sizes are measured in MB/GB (bytes). To convert: MBps = Mbps ÷ 8. So a 100 Mbps broadband connection transfers at most 12.5 MBps — meaning a 1 GB file takes at least 80 seconds, not 10.

Advertised broadband speeds are theoretical maximums measured under ideal conditions. Real-world speeds are reduced by: network congestion and shared bandwidth with neighbours, Wi-Fi overhead and signal attenuation (wired connections are faster), protocol overhead (TCP/IP headers, handshakes), server upload speed limits, and distance from the exchange. Typically expect 50–80% of the advertised speed in practice.

USB 2.0 maxes at 480 Mbps (60 MBps). USB 3.0/3.1 Gen 1 reaches 5 Gbps (625 MBps). USB 3.1 Gen 2 doubles it to 10 Gbps (1,250 MBps). USB4/Thunderbolt 3 hits 40 Gbps (5,000 MBps). However, actual speeds depend on both the cable and the device — a USB-C cable that only supports USB 2.0 speeds will bottleneck at 480 Mbps regardless.

A 1-hour 4K video at high bitrate is roughly 50–100 GB. On a 100 Mbps upload connection (12.5 MBps), a 50 GB file takes about 67 minutes theoretically. At real-world 50% efficiency (~6 MBps), expect around 2.3 hours. This calculator lets you enter your actual measured upload speed to get a precise estimate. Always measure your upload speed separately — most speed tests show download by default.

For very large datasets (multi-terabyte), physical media is often faster than any internet connection — this concept is called 'sneakernet'. A USB drive or NVMe SSD shipped overnight can move 8 TB at an effective transfer rate that would take weeks over the internet. Amazon's Snowball Edge service uses the same idea for cloud migrations. Use this calculator to compare how long your data would take over your current connection speed.