What is a Bandwidth / Download Time Calculator?
Internet plans are sold in megabits per second; files are measured in megabytes — an 8× difference that makes everyone underestimate download times.
Enter file size and connection speed for the ideal time plus a realistic ~85%-efficiency estimate.
How to use the Bandwidth / Download Time Calculator
- Enter the file size and unit.
- Enter your speed in Mbps.
- Read the ideal and realistic transfer time.
Frequently asked questions
Why does my 100 Mbps line download at ~12 MB/s?
Because 100 megaBITS ÷ 8 = 12.5 megaBYTES per second. That is the plan working exactly as sold.
Why the realistic estimate?
Protocol overhead, server limits and Wi-Fi loss typically cost 10–20% — the 85% figure is a fair middle.
Does this apply to uploads?
Yes, using your upload speed — often much lower than download on consumer plans.
What speed do I actually have?
Run any speed test at the time of transfer — advertised “up to” speeds are ceilings.