Data Transfer Time Calculator
Estimate how long a download or upload takes from the file size and connection speed.
Estimate download and upload time
The Data Transfer Time Calculator tells you how long a file will take to download or upload, based on its size and your connection speed. Enter the size and speed in whatever units you have, and get an instant estimate in days, hours, minutes, and seconds. It runs entirely in your browser.
The bits vs bytes catch
The single most common mistake in transfer-time math is mixing up bits and bytes. Internet speeds are quoted in bits per second (Mbps), while file sizes are in bytes (MB). Since one byte is eight bits, a 100 Mbps connection downloads at only about 12.5 MB per second. This calculator handles the conversion for you, so the estimate is correct whichever units you pick.
How to use it
- Enter the file size and choose KB, MB, GB, or TB.
- Enter your speed and choose the unit (Mbps, MB/s, etc.).
- Read the estimated transfer time.
Why it's an estimate
Real-world transfers rarely hit the theoretical maximum. Overhead from network protocols, server limits, Wi-Fi interference, congestion, and disk speed all reduce throughput. As a rule of thumb, actual speeds are often 10–30% below the quoted figure. Treat the result as a best-case estimate and expect real transfers to take a little longer.
Quick reference
| File | At 100 Mbps |
|---|---|
| 1 GB | ~80 seconds |
| 5 GB movie | ~7 minutes |
| 50 GB game | ~70 minutes |
Common uses
- Estimating how long a big download will take before you start.
- Comparing internet plans by real-world transfer times.
- Planning backups and large file uploads.
- Understanding the difference between Mbps and MB/s.
Private and free
All calculations run in your browser — nothing is uploaded. The tool is completely free with no sign-up.
Frequently asked questions
Why is my real download slower than this?
The estimate is best-case. Protocol overhead, server limits, Wi-Fi, and congestion typically reduce real speeds by 10–30%.
What's the difference between Mbps and MB/s?
Mbps is megabits per second; MB/s is megabytes per second. One byte is 8 bits, so 100 Mbps is about 12.5 MB/s.
Does it handle different units?
Yes. Choose KB/MB/GB/TB for size and Mbps/Gbps/MB/s for speed; the tool converts correctly.
Is it free?
Yes, completely free with no sign-up, running entirely in your browser.