About this calculator
Real downloads rarely reach the full plan speed, so an efficiency figure is included.
How to use it
- Enter the file size and unit.
- Enter your speed in Mbps.
- Adjust efficiency if needed.
The formula
Time = file size in bits ÷ (speed × efficiency)
- 8 bits
- in a byte
- efficiency
- share of plan speed actually reached
Worked example
A 4 GB file on 50 Mbps
- At full speed: 32,000 megabits ÷ 50 = 640 s, 10 min 40 s.
- At 85% efficiency: 12 min 33 s.
What the result means
Wired connections usually beat Wi-Fi for large downloads.
Assumptions
- Steady speed.
Limitations
- Servers can limit speed below your plan.
Frequently asked questions
How long does 1 GB take at 100 Mbps?
About 80 seconds at full speed.
Why is my download slower than my plan?
Wi-Fi, network load and the server all reduce speed.
What is the difference between Mbps and MB/s?
8 megabits make 1 megabyte.
Last reviewed on 3 October 2026. Found a mistake? Tell us.