帯域幅計算ツール
The detailed guide below is currently available in English.
Bits, bytes, and the ×8 rule
File sizes are measured in bytes while connection speeds are sold in bits, and there are eight bits to a byte. A 700 MB file is therefore 5,600 megabits, which takes 56 seconds at a full 100 Mbps. That multiplication is the whole core of the estimate — everything else adjusts for reality.
Why real downloads run slower
Advertised speeds describe the best case on the wire. Network protocol overhead, Wi-Fi signal quality, the remote server's own limits, and other devices sharing the connection each shave a slice. The overhead option discounts the raw speed so the estimate lands closer to what a file manager's progress bar will actually show.
よくある質問
Are MB here decimal or binary?
Decimal: 1 GB = 1000 MB and 1 MB = 1,000,000 bytes, matching how storage and connection speeds are marketed. Operating systems that report in MiB will show slightly smaller numbers.
What speed do I need to download X in Y minutes?
Divide the file size in megabytes by the seconds available, then multiply by 8 to get Mbps. The calculator rows show the effective throughput, which you can compare directly against that target.