Bandwidth Calculator
0 seconds to transfer
| Speed | Value |
|---|---|
| Kbps | |
| Mbps | |
| MB/s (megabytes/second) | |
| GB/hr (gigabytes/hour) |
Bits vs. Bytes: The Most Common Mix-Up
Internet speeds are advertised in bits per second (Mbps), but file sizes are measured in bytes (MB, GB). Since 1 byte = 8 bits, a "100 Mbps" connection has a theoretical ceiling of 100 ÷ 8 = 12.5 MB/s, not 100 MB/s. This calculator converts your file size to bits, divides by your connection's bits-per-second speed, and reports the result back in a human-readable time — using standard decimal (SI) units where 1 KB = 1,000 bytes, 1 MB = 1,000 KB, and so on, matching how ISPs and OS download managers report speed and size.
Why Real Downloads Are Slower Than the Rated Speed
No connection sustains its full rated bandwidth in practice. TCP/IP packet headers, encryption (TLS), Wi-Fi retransmissions, server-side throttling, and contention with other traffic on the network all eat into throughput — commonly costing 10-30% of the advertised rate, though this varies significantly by network and protocol. The "Real-World Overhead" field lets you knock a percentage off the ideal figure so the estimate better matches what you'd actually see; set it to 0% to view the pure theoretical transfer time instead.
Estimating Multi-File Transfers and Backups
The "Number of Files" field simply multiplies your single file size by the count, which works well for estimating bulk transfers like photo libraries or backups made up of many similarly sized files. For planning a home network or streaming setup around a given bandwidth budget, the conversion calculator can help translate between other data-rate and storage units, and the time duration calculator is useful for adding up several transfer windows across a day.
Frequently Asked Questions
Why does my download take longer than my internet speed suggests it should?
Advertised speeds are in bits per second (Mbps) while file sizes are in bytes, and 1 byte equals 8 bits, so a 100 Mbps connection tops out at 12.5 MB/s even in ideal conditions. On top of that, protocol overhead, Wi-Fi interference, and server throttling typically shave another 10-30% off real throughput, which is what the overhead field in this calculator accounts for.
What is the difference between Mbps and MB/s?
Mbps (megabits per second) is the unit ISPs use to advertise connection speed, while MB/s (megabytes per second) is the unit file managers and browsers use to show download progress. To convert, divide Mbps by 8: a 50 Mbps connection transfers at roughly 6.25 MB/s under ideal conditions.