How long will my download take?
This download time calculator tells you how long a file will take to download or upload at a given connection speed — a film over home broadband, a 100 GB game on fibre, a backup over a 4G hotspot. Enter the file size and the speed, and it allows for real-world overhead, explains the difference between megabits and megabytes, and shows a table of times at common speeds for typical files.
It also works the other way: tell it how much time you have, and it calculates the speed you would need — useful when choosing a broadband plan in India, the UK or the US, or planning a large upload to a client.
Everything is calculated in your browser. To find your real speed, run the internet speed test first and type the result here.
How to use the Download Time Calculator
- Enter the File size and its unit — or tap an example size such as an HD film or a large game.
- Enter your Connection speed. Internet plans are sold in megabits per second (Mbps); download managers often show megabytes per second (MB/s) — pick the matching unit.
- Adjust the Overhead if you like: 10% is a sensible default for TCP/IP and Wi-Fi losses.
- Read the time, the effective speed and how much you can transfer in an hour; press Play to watch a sped-up preview.
- Under Speed needed for a deadline, enter a time to see the connection speed required.
Download Time Calculator features
Mbps and MB/s
Speeds in Kbps, Mbps, Gbps, KB/s, MB/s or MiB/s; the result always shows both the effective megabits and megabytes per second.
Decimal or binary sizes
KB, MB, GB, TB (powers of 1000) as used by networks and storage makers, or KiB, MiB, GiB, TiB (powers of 1024) as Windows reports file sizes.
Realistic overhead
An adjustable allowance for protocol headers, retransmissions and Wi-Fi losses.
Reverse calculation
The speed you need to finish a transfer in a given number of hours, minutes and seconds.
Speed table
Ten common speeds from 1 Mbps to 10 Gbps against seven typical file sizes, with your speed highlighted.
Mbps vs MB/s — the factor of eight
Network speeds are measured in bits per second; file sizes in bytes. One byte is eight bits, so a 100 Mbps connection moves at most 12.5 megabytes per second. That is why a “100 meg” broadband line downloads a 1 GB file in about 80 seconds, not 10. In practice, around 5–10% of the capacity is taken by packet headers and acknowledgements, and Wi-Fi can lose much more, so 100 Mbps usually gives 11–11.9 MB/s at best.
A second, smaller trap is binary prefixes: Windows shows a “4.00 GB” file using 1 GiB = 1,073,741,824 bytes, so that file is really 4.29 billion bytes and takes 7% longer than a decimal 4 GB. Choose GiB when you copy a size from Windows Explorer. To convert between units on their own, use the data storage converter.
The formula and a worked example
Time (seconds) = file size (bytes) × 8 ÷ (speed (bit/s) × (1 − overhead)). For a 4 GB film at 100 Mbps with 10% overhead: 4,000,000,000 × 8 = 32,000,000,000 bits; 100,000,000 × 0.9 = 90,000,000 bit/s; 32,000,000,000 ÷ 90,000,000 = 356 seconds, or 5 minutes 56 seconds. To finish the same film in 10 minutes you need 32,000,000,000 ÷ 600 ÷ 0.9 ≈ 59.3 Mbps.
Why real downloads are slower
- The server or content network may be slower than your line, especially for game launchers and cloud storage at busy times.
- Wi-Fi far from the router, or through walls, can halve the speed; a cable is more consistent.
- Your speed is shared with everyone else using the connection, including background updates.
- Upload speeds on most home plans are much lower than download speeds — use the upload figure for backups and video uploads.
- For streaming and websites, think in sustained bandwidth instead — the bandwidth calculator covers that.
Download Time Calculator FAQ
How long does it take to download 1 GB at 100 Mbps?
About 80 seconds at the full line rate, or roughly 1 minute 29 seconds allowing 10% overhead. The download time calculator works it out for any size and speed.
How do I convert Mbps to MB/s?
Divide by 8: 100 Mbps = 12.5 MB/s, 50 Mbps = 6.25 MB/s, 1 Gbps = 125 MB/s.
Why is my download slower than my plan’s speed?
Overhead, Wi-Fi conditions, the server’s own speed and other devices sharing the line. Measure with a speed test and use that figure.
What overhead should I use?
5% for a wired connection to a fast server, 10% for typical home use, 20–30% for weak Wi-Fi or mobile data.
Does this work for uploads?
Yes — enter your upload speed instead of the download speed. Most home broadband uploads far more slowly than it downloads.
How big is a film or a game?
Very roughly: an HD film 3–5 GB, a 4K film 15–25 GB, a modern game 50–150 GB. Check the actual size in the store before you rely on the estimate. For video sizes from bitrate, see the video bitrate calculator.