Bandwidth and Download Time

Features

• ⚠️ Writes out the Mbps ÷ 8 = MB/s division instead of just giving a number
• Separate theoretical peak and effective speed (overhead adjustable)
• Times in plain words (“1 min 4 s”, not “00:01:04”), with fastest and realistic kept apart
• ⚠️ Both multipliers for every speed, as `62.5 MB/s = 59.6 MiB/s`. One "MB" means both 1000000 and 1048576 — ISPs and drive makers use the first, operating systems the second, and that gap is why a "1 TB" drive shows up as 931 GB
• ⚠️ The byte multiplier for the file size is a choice (decimal 1000 or binary 1024) because it changes the download time: the same "4 GB" differs by 7% between the two meanings
• Bandwidth units from bit/s to Tbps, five steps covering dial-up, broadband, gigabit and backbone
• The exact byte count under the file name, for reconciling against a drive or a download page
• Computed locally

How to use

1. Enter the bandwidth (the figure your ISP advertises, in Mbps)
2. Enter the file size and pick the unit
3. The effective speed and both times appear immediately
4. Adjust the overhead if your network differs

FAQ

500M broadband downloads at 62MB/s. Is that normal?

Normal, and nothing is missing. The 500M your provider sells is 500 Mbps (megabits per second), while download tools show MB/s (megabytes per second) — a factor of eight: 500 ÷ 8 = 62.5 MB/s. In practice it lands a few percent lower from protocol overhead, so 58–62 MB/s is expected. That is the number to check if you suspect short-changing, not a direct comparison of 500 with 62.

Why is the real speed below the theoretical figure?

Two reasons. First, protocol overhead: every packet carries an Ethernet header, an IP header and a TCP header (about 54 bytes together) plus the inter-frame gap, none of which is payload. Second, the other end and everything in between: the server’s uplink, the CDN node, Wi-Fi signal quality, other devices on your network. So the “effective” figure here removes only protocol overhead — a real download is usually slower still, and that gap is not something these parameters can express.

How many MB/s is 300 Mbps? (common plans at a glance)

300 Mbps is 37.5 MB/s — divide by 8. The same division covers the plans you are most likely to have: 100 Mbps = 12.5 MB/s, 200 = 25 MB/s, 300 = 37.5 MB/s, 500 = 62.5 MB/s, 1000 Mbps (gigabit) = 125 MB/s. Subtract a few percent for protocol overhead and you have the number a download tool actually shows.