Download Time Calculator
Enter the file size, your connection speed and how much of that speed you actually get. You get the download time and the effective speed.
Your numbers
How we calculate it
Speeds are measured in bits and file sizes in bytes, and one byte is 8 bits. The calculator turns the file size into bits (size in bytes × 8), turns the speed into bits per second and multiplies it by the efficiency, and then divides: time = bits ÷ (speed × efficiency).
So 1 GB (1,000,000,000 bytes) is 8,000,000,000 bits. At 100 Mbps and 100% efficiency that takes 80 seconds, and at 90% efficiency it takes 88.9 seconds, which is shown as 1 min 29 s.
Assumptions and limits
- Mbps (megabits per second) is not the same as MB/s (megabytes per second). A 100 Mbps connection moves at most 12.5 MB/s.
- Real downloads are slower than the line speed because of protocol overhead, the other side's speed, Wi-Fi and busy networks. The efficiency box is an estimate you choose, and 100% is the theoretical best.
- KB, MB, GB and TB are decimal (powers of 1,000). KiB, MiB, GiB and TiB are binary (powers of 1,024), which is how many operating systems show file sizes.
Frequently asked questions
How long does it take to download 1 GB?
At 100 Mbps with no losses it takes 80 seconds. At 10 Mbps it takes 800 seconds (13 min 20 s), and at 1 Gbps it takes 8 seconds.
Why is my download slower than my plan?
Plans quote the line speed in megabits per second. Overhead, Wi-Fi, other devices and the server all take a share, so 70 to 95 percent of the quoted speed is common. Lower the efficiency setting to model that.
What is the difference between Mbps and MB/s?
Mbps counts megabits and MB/s counts megabytes. There are 8 bits in a byte, so divide a speed in Mbps by 8 to get MB/s. 80 Mbps is 10 MB/s.
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Worked example (a fixed example using the starting numbers, it does not change as you type)
Inputs: File size = 1; File size unit = GB (gigabytes); Connection speed = 100; Speed unit = Mbps (megabits per second); Efficiency (% of the speed you really get) = 100.
- Download time 1 min 20 s
- Total seconds 80
- Effective speed 100 Mbps (12.5 MB/s)
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