Download Time Calculator

Download and upload times depend on two numbers that are usually written in different units: file sizes in bytes (MB, GB) and internet speeds in bits per second (Mbps). This calculator converts between them, allows for protocol overhead, and tells you how long a file takes — or, in reverse, how fast a connection must be to move it within a deadline. It works for game downloads, cloud backups, video uploads and copying over a network.

How to use this tool

1. Enter the file size and pick its unit (GB for downloads, GiB if your operating system shows binary units).
2. Enter your connection speed and its unit.
3. Leave about 10% overhead for real-world transfers, or 0% for the theoretical minimum.
4. For a deadline, switch to "Speed needed" and enter the target time.

Formula

time = size in bits ÷ (speed in bits/s × (1 − overhead))

Size in bits = bytes × 8. Decimal units use powers of 1,000 (1 GB = 10⁹ bytes); binary units use powers of 1,024 (1 GiB = 1,073,741,824 bytes) — Windows shows GiB but labels them GB. A speed in MB/s is 8 times the same number in Mbps.

Example

A 4.7 GB file is 4.7 × 10⁹ × 8 = 37.6 billion bits. On a 25 Mbps line with no overhead it takes 37.6 × 10⁹ ÷ 25 × 10⁶ = 1,504 seconds (25 min 4 s). With a realistic 10% overhead, a 100 Mbps connection needs 376 ÷ 0.9 ≈ 418 s, about 7 minutes. 1 GB at 100 Mbps takes exactly 80 seconds in theory.