How download time is calculated
Download time is just size divided by speed, once both are in the same units. The catch is that file sizes are measured in bytes and internet speeds in bits. A byte is 8 bits, so a "300 meg" plan moves at most 37.5 megabytes each second.
The formula
MB/s = Mbps ÷ 8
Example: a 100 GB game on 300 Mbps
| Step | Result |
|---|---|
| Size in bits: 100 × 10⁹ × 8 | 800 billion bits |
| Theoretical: 800 × 10⁹ ÷ 300 × 10⁶ | 44 min 27 s |
| At 90% efficiency | 49 min 23 s |
| Speed in MB/s: 300 × 0.9 ÷ 8 | 33.8 MB/s |
Typical download times for 100 GB
| Speed | Theoretical |
|---|---|
| 25 Mbps | 8 h 53 min |
| 100 Mbps | 2 h 13 min |
| 300 Mbps | 44 min |
| 500 Mbps | 27 min |
| 1 Gbps | 13 min |
Speeding up big downloads
- Use Ethernet. A cable is almost always faster and steadier than Wi-Fi, especially for consoles.
- Pause other traffic. Streaming and cloud backups on other devices share the same connection.
- Check your drive. On fast fiber, an old hard drive can be slower than the connection while a game installs.
Frequently asked questions
Why is my download in MB/s slower than my Mbps speed?
Internet speeds are sold in megabits per second (Mbps), while download apps show megabytes per second (MB/s). There are 8 bits in a byte, so a 300 Mbps plan downloads at most about 37.5 MB/s. That's normal, not a fault.
How long does a 100 GB game take to download?
At 100 Mbps, about 2 hours 13 minutes in theory and around 2.5 hours in practice. At 300 Mbps, about 45 minutes in theory; at 1 Gbps, about 13 minutes, though game servers and your storage drive can limit it.
What does the efficiency setting mean?
Real downloads lose some speed to network protocol overhead, Wi-Fi signal, other devices sharing the connection and the server's own limits. 85 to 90% of the plan speed is typical on a good wired connection; Wi-Fi is often lower.
Is a GB 1,000 MB or 1,024 MB?
Network speeds and download stores almost always use decimal units, so this calculator treats 1 GB as 1,000 MB. Windows reports file sizes in binary units (1 GB = 1,024 MB), which is why a file can look slightly bigger in a store than in File Explorer.
How do I check my real internet speed?
Run a speed test from a computer connected by Ethernet, with other devices paused. Use the download result for downloads and the upload result for backups and uploads, which are usually much slower on cable and DSL plans.
Rates and figures last checked October 2026.
This calculator gives estimates for planning. Check current rates and product labels before you buy, list or file.