What Is a Bandwidth Calculator?
This calculator estimates how long a file transfer or download will take, based on file size and your connection speed — accounting for the common confusion between megabytes (file size) and megabits (connection speed).
How to Use the Bandwidth Calculator
- Enter your file size and select its unit (MB, GB, or TB).
- Enter your connection speed in Mbps (megabits per second).
- View the estimated transfer time.
Bandwidth Formula
Worked Example
File size: 10 GB = 10,240 MB = 81,920 megabits
Transfer time: 81,920 ÷ 100 ≈ 819 seconds ≈ 13 minutes 39 seconds
Why Megabits vs. Megabytes Matters
Internet speeds are advertised in megabits per second (Mbps), while file sizes are typically shown in megabytes (MB). Since 1 byte = 8 bits, a "100 Mbps" connection transfers at most about 12.5 MB per second under ideal conditions — a common source of confusion when estimating download times.
Common Mistakes to Avoid
- Confusing Mbps (megabits) with MBps (megabytes) — an 8x difference.
- Expecting to hit your maximum advertised speed consistently — real-world speeds are often somewhat lower due to network overhead and congestion.
Frequently Asked Questions
Mbps (megabits per second) is the standard way internet speeds are advertised. MBps (megabytes per second) is typically used for file sizes. Since 1 byte = 8 bits, MBps is roughly 8 times smaller than the equivalent Mbps figure.
Network overhead, other devices sharing the connection, server-side limitations, and network congestion can all reduce actual achievable speeds below the advertised maximum.
Divide the Mbps value by 8. For example, 100 Mbps equals approximately 12.5 MB per second under ideal conditions.
Approximately 13-14 minutes under ideal conditions, though real-world speeds are often somewhat lower than the maximum rated speed.
No — it calculates a theoretical estimate based on the stated speed; actual transfer times are often somewhat longer due to overhead and network conditions.