Download Time Calculator

Estimate transfer time from file size and speed, or find the connection speed needed to meet a deadline.

Calculation mode

File size

Connection speed (download or upload)

File size convention

Available transfer window (hours)

Protocol overhead: 10%

Real-world throughput: 100%

Lower "real-world throughput" to simulate congestion, Wi-Fi loss or a busy server.

Estimated time

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Speed	Time for this file

How the calculation works

Time = file size in bits ÷ effective speed. In reverse mode, the calculator finds the nominal connection speed needed for the chosen transfer window, accounting for the selected overhead and throughput assumptions. Choose decimal (base 1000) or binary (base 1024) units to match the reported file size. Speeds use 1 Mbps = 1,000,000 bit/s and 1 MB/s = 8 Mbps. This is an estimate, not a transfer measurement or schedule.

Why is my real download slower than the advertised speed?

Advertised speeds are line rates. TCP/IP headers, Wi-Fi interference, server-side limits and other devices on your network can reduce the throughput you actually get. Upload and download speeds vary by connection and plan; use the relevant measured or advertised rate for your transfer direction.

Mbps vs MB/s

Internet plans are sold in megabits per second (Mbps). Download managers usually show megabytes per second (MB/s). One byte is 8 bits, so a 400 Mbps connection tops out around 50 MB/s before overhead.