Download Time Calculator

Estimate download and upload times

This calculator estimates how long a file will take to transfer given its size and your connection speed. The key subtlety it handles correctly is the difference between bits and bytes: connection speeds are quoted in megabits per second, while file sizes are measured in megabytes, and there are eight bits in a byte. The tool converts both to a common unit before dividing, so a five gigabyte file over a one hundred megabit connection correctly comes out around four hundred seconds, not fifty.

An optional ten percent overhead allowance accounts for the protocol headers, acknowledgements and retransmissions that mean real throughput is always a little below the headline speed.

Why transfer-time estimates help

Knowing roughly how long a download will take helps you plan backups, software rollouts, media transfers and cloud migrations. It also reveals when a connection is underperforming: if a transfer takes far longer than the estimate, something is throttling it. The same calculation works for uploads by entering your upload speed.

Remember that quoted connection speeds are a maximum under ideal conditions, and shared links, distance to the server and disk speed can all reduce real throughput. Treat the result as a best-case estimate. All calculation runs locally in your browser.

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