Divide Mbps by 8 to get MB/s. 100 Mbps = 12.5 MB/s , 1 Gbps = 125 MB/s . In practice expect about 10-15% less than the arithmetic, because protocol overhead is not payload.
Enter your measured speed below to see MB/s, KB/s and Gbps plus realistic download times for common file sizes.
Internet speed is sold in megabits per second (Mbps) but files are stored in megabytes (MB) . There are 8 bits in a byte, so a 100 Mbps line downloads at roughly 12.5 MB/s in real conditions. Use the converter below to translate any plan speed into practical units.
Even on a clean Ethernet connection you'll see 10-15% lower than the advertised number, due to TCP/IP overhead, framing, and retransmissions. Add WiFi to the mix and you can lose another 30-50%.
This is why a "300 Mbps" plan shows roughly 35 MB/s in Chrome's download bar. Nothing is wrong — the two figures are the same speed in different units, minus overhead.
Every payload byte travels inside Ethernet, IP and TCP headers, and TLS adds its own framing. That structural cost is roughly 5-8% on a healthy line; retransmissions after packet loss, plus the slow-start ramp at the beginning of every transfer, take the rest. Short downloads therefore average lower than long ones, because the ramp is a larger share of the transfer.
The table above assumes your full measured speed goes to one transfer. In real use it rarely does: another device streaming 4K takes 25 Mbps, a cloud backup competes for the same link, and a slow origin server can cap you far below your plan. If a single download is much slower than this calculator predicts while a speed test reads normally, the bottleneck is the server or your WiFi, not your plan.
Working out whether the plan itself is large enough for your household is a different question — our bandwidth calculator covers that.
Storage vendors use 1,000; operating systems traditionally use 1,024. This converter uses 1,024 for KB/s, which is what Windows and most download managers display, and 1,000 for the Mbps-to-Gbps step, which is what network equipment uses.
On cable and most DSL plans upload is capped by design, often at a tenth of the download figure. Fibre plans are usually symmetric. If you need more upload, see how to improve upload speed .
Netflix recommends 15-25 Mbps for 4K, which is about 2-3 MB/s. A 100 Mbps line carries four such streams with room to spare.