Download Time Calculator
Minutes, not marketing megabits.
Download Time Calculator
Seconds = (File size in MB × 8) / (Speed in Mbps × efficiency)
Calculated instantly
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What This Calculator Does
The Download Time Calculator converts a file size and a connection speed into seconds, minutes, and hours, with an efficiency allowance for the gap between a headline speed and real throughput.
How It Works
File sizes are in bytes and connection speeds in bits, so the size is multiplied by eight. Dividing by the effective speed in megabits per second gives seconds. Efficiency reduces the headline speed to reflect protocol overhead, Wi-Fi contention, and server throttling.
Example
A 1,500 MB file over a 100 Mbps connection at 90% efficiency takes 1,500 × 8 / 90 = 133.3 seconds, or about 2.2 minutes. Throughput is 11.25 MB/s. At 50% efficiency the same file takes four minutes.
Formula
Seconds = (Size in MB × 8) / (Speed in Mbps × efficiency)MB/s = Mbps × efficiency / 8Reading the Results
Download time in seconds
The raw transfer estimate at your chosen efficiency. It excludes connection setup, authentication, and any time spent waiting on the server.
Effective throughput
The megabytes per second you should actually expect, after the efficiency allowance. Compare it with the MB/s figure a download manager reports.
Sources and References
IEC 80000-13 — Quantities and units: information science
Definitions of the bit, byte, and binary prefixes
Clarifies why MB and Mbps differ by a factor of eight, and the difference between decimal and binary prefixes.
RFC 6298 — Computing TCP Retransmission Timer
Retransmission and round-trip overhead
Illustrates why real throughput sits below the link rate, particularly on high-latency paths.
References identify the method or data behind this calculator. Where a standard or tariff changes, the current edition applies, and the assumptions stated above take precedence over a remembered figure.
Frequently Asked Questions
Why is my download slower than the speed I pay for?
The headline figure is a link rate in megabits per second, not megabytes. Divide by eight for the theoretical MB/s, then subtract overhead. A 100 Mbps line tops out near 12.5 MB/s, and usually delivers 10–11 MB/s.
Does distance affect download speed?
Yes. Higher latency increases the impact of TCP slow start and retransmissions, so a distant server can be slower even on the same connection. Throughput also depends on the server’s upload capacity.
What efficiency should I enter?
Ninety percent is a reasonable wired default. Use 70–80% for congested Wi-Fi or busy shared connections, and lower still for mobile networks or intercontinental transfers.
Can I use this for uploads?
Yes, the arithmetic is identical, but upload speeds are often a fraction of download speeds on residential connections. Enter your measured upload rate rather than the advertised download rate.