Data Transfer Time Calculator

Data transfer speed and time calculations live or die on unit notation, and the industry runs two parallel conventions at once.
Decimal, base 10, is used for drive capacity and every network speed you will ever be quoted. Binary, base 2, is what your operating system uses when it reports a file size. They differ by about 7% at the gigabyte and the gap widens as the units get bigger, which is where most of the confusion on this subject comes from.

The fundamental formula:

Transfer Time = File Size ÷ Transfer Speed

Critical unit conversions:

Converting file size to bits for transfer calculation:

File Size in Bits = File Size (GB) × 1,073,741,824 × 8

Transfer Time (seconds) = File Size (bits) ÷ Speed (bps)

Worked example: Upload a 4 GB video file on a 100 Mbps internet connection:

• File size: 4 GB × 1,073,741,824 bytes × 8 bits = 34,359,738,368 bits
• Speed: 100 Mbps = 100,000,000 bits per second
• Time: 34,359,738,368 ÷ 100,000,000 = 343.6 seconds ≈ 5 minutes 44 seconds

Note: Real-world speeds are typically 60–80% of advertised speeds due to protocol overhead, network congestion, and latency.

Real-world speed reference. Every row below treats 1 GB as the binary 1,073,741,824 bytes, which is the figure your operating system shows and the one the calculator uses. Read it as decimal and each of these gets about 7% quicker.

Those are the theoretical figures. None of them include protocol overhead, and USB in particular never gets close: USB 2.0’s 480 Mbps is the signalling rate, and a real bulk transfer lands around 320.