Download Time Calculator
This download time calculator works out how long a file takes from its size and your connection speed. A 4.7 GB file at 100 Mbit/s takes 6 minutes 16 seconds under ideal conditions and 7 minutes 50 seconds at a realistic 80% efficiency.
Example: File size 4.7 · Size unit: Gigabytes (GB) · Counting: Decimal (1 GB = 1,000 MB) · Speed 100 · Speed unit: Megabits per second (Mbit/s) · Real-world efficiency 100 % → Duration: Download time: 6 min 16 s. Source: Wikipedia – Binary prefix: kilobyte, megabyte, gigabyte (decimal) versus kibibyte, mebibyte, gibibyte (binary). Updated: .
How it is calculated
How to calculate download time
The duration is the amount of data divided by the speed. Because files are given in bytes and connections in bits per second, use seconds = size in bytes × 8 ÷ bits per second. 4.7 GB is 4.7 × 10⁹ bytes, which is 37.6 billion bits; at 100 Mbit/s that takes 376 seconds, or 6 minutes 16 seconds.
Bits, bytes and prefixes
- 1 byte = 8 bits. So 100 Mbit/s is at most 12.5 MB/s.
- Decimal: 1 MB = 1,000,000 bytes, 1 GB = 10⁹ bytes. This is how manufacturers and providers quote.
- Binary: 1 MiB = 1,048,576 bytes, 1 GiB = 1,073,741,824 bytes. Some operating systems call this “GB”.
Why it takes longer
The rated speed rarely arrives in full. Protocol overhead, Wi-Fi reception, server load and other devices on the network slow it down. The “Real-world efficiency” field gives a more realistic value; 80% is a sensible starting point.
Limits
The time is an estimate at constant speed. Fluctuating connections, throttling after a data cap and resuming after an interruption are not included. Upload speeds are often much lower than download speeds.
Frequently asked questions
How do you calculate download time?
File size in bytes times 8, divided by the speed in bits per second. 1 GB at 100 Mbit/s takes 80 seconds.
How many MB per second is 100 Mbit/s?
At most 12.5 MB/s, because a byte has 8 bits. In practice a little less arrives.
Why is my download slower than calculated?
Because protocols, Wi-Fi, server load and other devices lower the rated speed. Try 70 to 90% efficiency.
What is the difference between Mbit/s and MB/s?
Mbit/s are megabits, MB/s megabytes per second. A byte has 8 bits, so 1 MB/s equals 8 Mbit/s.
How long does it take to download 50 GB?
At 100 Mbit/s and full efficiency about 1 hour 7 minutes, at 80% efficiency about 1 hour 23 minutes.
Sources and legal basis
- Wikipedia – Binary prefix: kilobyte, megabyte, gigabyte (decimal) versus kibibyte, mebibyte, gibibyte (binary)
- Wikipedia – Data-rate units: bit per second, megabit per second, megabyte per second
As of: · Editorial policy
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