Do my inputs leave the browser?

No. The estimate is computed locally with simple arithmetic. Nothing is sent to any server.

What is the difference between GB and GiB, or Mbps and MB/s?

GB/MB/KB/TB are decimal (1 GB = 10⁹ bytes) while KiB/MiB/GiB are binary (1 GiB = 2³⁰ bytes) — operating systems often report the binary sizes. Mbps measures megabits per second, MB/s megabytes per second; 1 MB/s equals 8 Mbps, which is why a "100 Mbps" line downloads at roughly 12.5 MB/s.

Why do real downloads take longer than the estimate?

The result assumes the link runs at full nominal speed for the whole transfer. TCP slow start, protocol overhead, server throughput limits, Wi-Fi conditions, and shared contention all reduce effective speed, so real-world times are typically somewhat longer.

Download Time Calculator

Overview

“How long will 50 GB take on this connection?” comes up when planning OS images, game downloads, backups, or data migrations. This calculator converts a file size and a link speed into an estimated duration, handling the two unit traps that cause most wrong answers: decimal vs binary sizes (GB vs GiB) and bits vs bytes (Mbps vs MB/s).

How to use

Enter the size in the File size field and pick a unit: decimal KB/MB/GB/TB or binary KiB/MiB/GiB.
Enter the link speed under Connection speed and pick Kbps, Mbps, Gbps, KB/s, or MB/s.
Read Estimated time, shown as hours, minutes, and seconds.

Examples

1 GB at 100 Mbps → 1m 20.0s
700 MB at 10 Mbps → 9m 20.0s
100 GB at 1 Gbps → 13m 20.0s

Notes

The formula is size in bits divided by speed in bits per second — a theoretical best case, as the tool itself notes. Expect real transfers to run slower due to overhead and contention; a 10–20% margin is a reasonable rule of thumb on a healthy wired link, more on Wi-Fi.