Bandwidth / Download Time Calculator
Calculate estimated download time for a file given its size and your connection speed.
Progress through the download at a steady 100 Mbps connection — real-world speeds fluctuate, so treat this as a best case.
About the Bandwidth / Download Time Calculator
This calculator estimates how long a file will take to download given its size and your connection speed — a genuinely confusing conversion since file sizes are measured in bytes (MB, GB) while connection speeds are almost always advertised in bits (Mbps, Kbps).
It comes up when checking whether a large game download or software update will finish before you need to leave, when comparing internet plans by what they'd actually mean for a typical download, or just double-checking why an advertised "100 Mbps" connection doesn't download a 100 MB file in one second.
Pick your file size unit and connection speed unit independently, and the calculator handles the bits-to-bytes conversion internally so you don't have to do the math by hand.
How it’s calculated
The most common source of confusion here is that file sizes are measured in bytes, but internet speeds are marketed in bits — and there are 8 bits in a byte. A "100 Mbps" connection transfers about 12.5 megabytes per second, not 100 megabytes per second, which catches a lot of people off guard when a download takes far longer than the advertised speed number implies.
The calculator converts your file size to bits (multiplying by 8) and your connection speed to bits per second, then divides one by the other to get download time in seconds — this is a theoretical best case, since it assumes your connection sustains its full advertised speed for the entire download with no overhead or contention.
Frequently asked questions
Why is my download slower than my internet plan's advertised speed suggests?
Advertised speeds are almost always in megabits per second (Mbps), while file sizes and download progress bars show megabytes (MB) — since there are 8 bits per byte, a 100 Mbps connection tops out around 12.5 MB per second, not 100 MB per second, which is often the real explanation.
What's the difference between Mbps and MBps?
Mbps (lowercase b) is megabits per second, the unit internet speeds are marketed in. MBps (uppercase B) is megabytes per second, the unit download managers and file sizes use. Dividing Mbps by 8 gives you the roughly equivalent MBps figure.
Why does my actual download take longer than this calculator predicts?
This estimate assumes your connection sustains its full advertised speed the entire time, with no other devices competing for bandwidth and no server-side bottleneck. Real downloads are affected by network congestion, Wi-Fi signal strength, and the download server's own speed limits — all of which this calculator doesn't account for.
How much faster is a wired connection than Wi-Fi for large downloads?
It depends heavily on your specific Wi-Fi setup and signal strength, but a wired Ethernet connection generally delivers closer to your plan's actual advertised speed with less variability than Wi-Fi, which can be affected by distance, interference, and how many devices share the network.
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