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Bandwidth Calculator

Estimated Download Time

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Understanding Bandwidth & Download Time

Bandwidth measures how much data your internet connection can transfer per second. Download time depends on two factors: file size (in GB/MB) and your internet speed (in Mbps or Gbps). The key confusion? Bits vs. Bytes.

Internet speeds are advertised in megabits per second (Mbps), but file sizes are shown in megabytes (MB). Since 1 byte = 8 bits, a 100 Mbps connection downloads at roughly 12.5 MB/s (divide by 8). That's why your "100 Mbps fiber" doesn't download a 100MB file in 1 second—it takes about 8 seconds.

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Expert Tip: Real-World Speeds
Your actual download speed is usually 70-80% of advertised speeds due to network overhead (packet headers, error correction) and server limitations. A 100 Mbps plan typically delivers 70-80 Mbps in practice. Use wired Ethernet instead of Wi-Fi for maximum speed—Wi-Fi adds 15-30% overhead depending on interference and router quality.

Common Mistakes When Estimating Download Time

  • Confusing Mbps with MBps: Remember, 100 Mbps ≠ 100 MB/s. Divide by 8 to convert.
  • Ignoring Network Overhead: TCP/IP adds ~20% overhead, so you never get 100% of theoretical speed.
  • Forgetting Server Limitations: Even with 1 Gbps internet, a slow server may only upload files at 10 MB/s.
  • Wi-Fi vs. Wired: Wi-Fi 5 (802.11ac) tops out around 400-600 Mbps real-world, even if your plan is 1 Gbps.
  • Multiple Devices: Bandwidth is shared. If 3 devices use a 100 Mbps connection, each gets ~33 Mbps.

Bandwidth Requirements by Use Case

  • HD Streaming (1080p): 5 Mbps per stream (Netflix, YouTube)
  • 4K Streaming: 25 Mbps per stream (Netflix 4K = 25 Mbps, YouTube 4K = 20 Mbps)
  • Online Gaming: 3-6 Mbps (latency matters more than speed)
  • Video Calls (Zoom/Teams): 1-4 Mbps per participant
  • Large File Downloads (100GB game): At 100 Mbps → ~2 hours; at 1 Gbps → ~15 minutes
AS
Reviewed by Alex Stevenson, Network Engineer
Updated November 26, 2025

Frequently Asked Questions

How do I calculate download time?

Download time = File Size ÷ Internet Speed. For example, a 10GB file at 100Mbps takes about 13 minutes. Remember to convert units properly: 1 byte = 8 bits, so 100Mbps = 12.5MB/s.

What's the difference between Mbps and MBps?

Mbps (megabits per second) measures internet speed, while MBps (megabytes per second) measures download speed. 1 MBps = 8 Mbps. ISPs advertise in Mbps, but downloads show MBps.

Why is my actual download slower than my internet speed?

Real-world downloads are typically 70-80% of advertised speeds due to network overhead, server limitations, Wi-Fi interference, and multiple devices sharing bandwidth. Wired connections are usually faster than Wi-Fi.

How much bandwidth do I need for 4K streaming?

4K streaming requires 25-50 Mbps per stream. Netflix recommends 25Mbps for 4K, while YouTube suggests 20Mbps. Add 10-20 Mbps per additional user for smooth performance.

Is 100 Mbps fast internet?

Yes, 100 Mbps is considered fast for most households. It supports 4K streaming on 2-3 devices, online gaming, and large file downloads. A 5GB game downloads in about 7 minutes at 100Mbps.