Download Time Calculator
How long a file takes to download at your connection speed.
Input sheet
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The gap between a 100-megabit plan and a 50-gigabyte game download is where most people's estimates fall apart — because plans are sold in bits and files are measured in bytes. This calculator does the unit bridge and gives a real clock time.
How it works
Seconds = size in gigabits ÷ speed in Mbps, where 1 GB = 8,000 megabits. Your plan speed is in bits; file sizes are in bytes — the ÷8 is where estimates usually go wrong.
Connection speeds (Mbps) are megaBITS per second; file sizes (GB, MB) are BYTES, eight times larger per unit. One gigabyte is 8,000 megabits in the decimal convention ISPs and drive makers use, so a 50 GB file is 400,000 megabits — divide by your Mbps and you have seconds.
Real downloads run below the plan number: protocol overhead, Wi-Fi loss, server-side limits, and other devices on the line typically leave you 70–90% of advertised speed. Treat the result as a best case, and plug in a measured speed-test number for a tighter estimate.
Seconds = file size (GB) × 8,000 ÷ speed (Mbps). Transfer rate in MB/s = Mbps ÷ 8.
Worked examples
A 50 GB game on a 100 Mbps connection. → About 1 hr 7 min.
50 × 8,000 = 400,000 megabits ÷ 100 = 4,000 seconds ≈ 66.7 minutes.
A 15 GB 4K movie on 500 Mbps fiber. → 4 minutes flat.
15 × 8,000 ÷ 500 = 240 seconds.
Tips & gotchas
- Run a speed test and use that number instead of your plan's — it folds in Wi-Fi and network reality automatically.
- For big downloads, a cable to the router routinely doubles real-world speed versus Wi-Fi across the house.
- Uploads are the same math with your (usually much smaller) upload speed — a 20 Mbps upload moves that 50 GB in over five hours.
FAQ
Why is my real download slower?
Overhead, Wi-Fi loss, server limits, and other devices sharing the line. Expect 70–90% of the advertised speed on a good day.
Why is my download slower than advertised?
Overhead, Wi-Fi signal loss, a throttled or busy server, and other household traffic all shave the rate. Getting 80% of the plan speed on a good connection is normal.
Is a gigabyte 1,000 or 1,024 megabytes?
Both conventions exist: ISPs and storage marketing use decimal (1,000), operating systems often use binary (1,024). This calculator uses decimal, which matches how connection speeds are sold; the difference is under 3% at these scales.
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