Internet Speed Calculator
Connection speed is quoted in megabits per second, but file sizes are usually in gigabytes — mixing bits and bytes is exactly why a '100 Mbps' connection doesn't download a '100 MB' file in one second.
Inputs
Result
6.42 minutes
385 seconds at 100 Mbps
How the internet speed calculator works
Download time (seconds) = (file size in GB × 8 × 1,024) ÷ speed in Mbps.
The ×8 converts gigabytes to gigabits (since connection speed is measured in bits, not bytes); ×1,024 converts gigabits to megabits.
Worked example: 4.7 GB file (a standard DVD image), 100 Mbps connection
- Seconds = (4.7 × 8 × 1,024) ÷ 100 = 38,502.4 ÷ 100 = 385.024 seconds.
- In minutes: 385.024 ÷ 60 ≈ 6.42 minutes.
Common mistakes to avoid
Confusing megabits (Mbps) with megabytes (MB) per second
Internet speeds are marketed in megabits per second, but file sizes are shown in megabytes — 1 byte equals 8 bits, so a '100 Mbps' connection downloads at roughly 12.5 megabytes per second, not 100.
Expecting to actually achieve the full advertised speed
Advertised speed is typically a maximum under ideal conditions — real download speed is often reduced by network congestion, Wi-Fi signal quality, server-side limits, and other simultaneous usage on the connection.
Frequently asked questions
Why does '100 Mbps' feel much slower than 100 megabytes per second?
Because Mbps measures megabits, not megabytes — divide by 8 to get the theoretical maximum megabytes per second, so 100 Mbps translates to roughly 12.5 MB/s at best.
Why might my actual download be slower than this calculation predicts?
This is a theoretical best-case figure — real speeds are affected by network congestion, the specific server's upload capacity, Wi-Fi conditions, and other devices sharing the same connection simultaneously.
How is GB different from GiB in this context?
This calculator uses 1,024 as the conversion factor (binary/GiB convention) rather than 1,000 (decimal/GB convention) — the difference is small but not zero for very large files.
What speed do I actually need for smooth video streaming?
This varies by resolution — standard definition typically needs a few Mbps, while 4K streaming commonly recommends 25 Mbps or more, according to most major streaming services' own guidance.
Related calculators
Electricity Bill Calculator
Monthly electricity cost from appliance usage.
Screen Time Calculator
How much of your life goes to screens.
Password Strength Calculator
Entropy and estimated crack time for a password.
Binary Converter
Convert decimal numbers to binary and back.
File Transfer Time Calculator
How long a download or upload will take.