Bandwidth Calculator — Free Online Tool
Estimate download or transfer time from file size and connection speed.
About Bandwidth Calculator
The Bandwidth Calculator estimates how long it takes to download or transfer a file at a given connection speed. Enter the file size and the speed, choose your units, and get the time broken down into days, hours, minutes and seconds.
It's useful for planning large downloads, backups, uploads, and data migrations. The result is a theoretical best case; real-world transfers are a little slower due to overhead. Everything runs locally in your browser.
How to Use Bandwidth Calculator
- Enter the file size and choose its unit (KB, MB, GB, TB).
- Enter the connection speed and choose its unit (Kbps, Mbps, Gbps, MB/s).
- Click Calculate.
- Read the estimated transfer time.
Key Features
Supports bit-based (Mbps) and byte-based (MB/s) speeds
File size units from KB to TB
Clear breakdown in days/hours/minutes/seconds
Instant, no signup
100% client-side and private
Frequently Asked Questions
How is download time calculated?
Time = file size in bits divided by speed in bits per second. The tool converts your chosen size and speed units to bits and bits/second, then formats the result in days, hours, minutes and seconds.
What's the difference between Mbps and MB/s?
Mbps is megabits per second (used by ISPs); MB/s is megabytes per second. 1 byte = 8 bits, so 80 Mbps equals 10 MB/s. The tool handles both.
Does it account for overhead?
No. It gives a theoretical best-case time. Real transfers are slower due to protocol overhead, latency, and congestion — typically 5–20% longer.
Is my input private?
Yes. The calculation runs entirely in your browser with no uploads.