Estimate how long a file takes to download at a given connection speed.
Calculated instantly in your browser.
How do you calculate file download time?
Time = file size in bits ÷ speed in bits per second. Remember 1 byte = 8 bits, so a 100 Mbps line moves about 12.5 MB per second. For example, a 5 GB file on a 100 Mbps connection takes about 6 minutes 40 seconds. This is a best-case estimate; real transfers are slower due to overhead and congestion.
Understanding your result
This is a best-case estimate. Real transfers are slower because of protocol overhead, network congestion and disk speed.
Formula and method
Time = file size in bits ÷ speed in bits per second. Remember 1 byte = 8 bits, so a 100 Mbps line moves about 12.5 MB per second.
Assumptions and limitations
This is a best-case theoretical estimate based on raw speed and file size. Real downloads are slower because of protocol overhead, network congestion, server limits, latency, and disk write speed. The figure assumes your connection sustains its full rated speed throughout, which rarely happens in practice.
Worked example
A 5 GB file on a 100 Mbps connection takes about 6 minutes 40 seconds.
How to use this tool
- Enter the file size and its unit.
- Enter your connection speed and its unit.
- Press Calculate.
About the Download Time Calculator
The Download Time Calculator estimates how long a file takes to transfer at a given internet speed, correctly handling megabits versus megabytes.
Who should use this tool
Anyone estimating how long a transfer will take: developers sizing a build artifact download, IT staff planning a large backup or file distribution, and users deciding whether a game or video will finish in time. The tool correctly handles the common megabit-versus-megabyte confusion.
Benefits
- Correctly converts between megabits and megabytes
- Estimates transfer time from size and connection speed
- Helps you plan around large downloads or backups
- Calculates instantly in your browser with nothing uploaded
Practical use cases
- Estimating how long a large game download will take
- Planning a big backup transfer over a link
- Comparing download times across connection speeds
- Checking whether a file will finish before a deadline
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Frequently asked questions
Why is my download slower than this?
Advertised speeds are maximums. Overhead, shared bandwidth, server limits and Wi-Fi all reduce real-world throughput.
Why is my real download slower than the estimate?
The estimate assumes your connection runs at its full rated speed with no overhead. In reality, protocol overhead, network congestion, server-side limits, latency, and your disk's write speed all reduce throughput. Shared connections and Wi-Fi interference slow things further, so actual transfers usually take longer than the ideal figure.
How many megabytes per second is a 100 Mbps connection?
Because one byte is eight bits, you divide the megabit rate by eight. A 100 Mbps connection therefore moves about 12.5 megabytes per second at best. This is why a line advertised in megabits downloads files, measured in megabytes, far slower than the headline number suggests.