Data Transfer Time Calculator
Calculate how long a file transfer or download will take based on file size and connection speed, free in your browser.
Enter Values
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How to use this calculator
- Enter the file size in MB (1 GB = 1000 MB).
- Enter your connection speed in Mbps.
- Read the estimated transfer time.
How it works
The Data Transfer Time Calculator estimates how long a download or upload takes from the file size and the link speed. The catch most people miss: file sizes are in bytes (MB) but speeds are in bits (Mbps), and there are 8 bits in a byte.
Time (seconds) = file size in MB × 8 ÷ speed in Mbps. The result is a theoretical best case; real transfers run 10–30% slower because of protocol overhead, network contention and disk speed.
Worked example
A 1.5 GB file on a 100 Mbps line. 1500 MB × 8 ÷ 100 = 120 seconds (2 minutes) at best.
Frequently asked questions
Why isn't 100 Mbps the same as 100 MB per second?
Speeds are quoted in megabits (Mbps) but files are measured in megabytes (MB), and a byte is 8 bits. So 100 Mbps is about 12.5 MB per second, not 100.
Why is my real download slower?
Overhead, shared bandwidth, server limits and your disk all add up. A 10–30% margin over the theoretical time is typical.
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Cite this tool
Zerdly. (2026). Data Transfer Time Calculator. Retrieved from https://www.zerdly.com/tools/data-transfer-time-calculator/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.