Bits vs Bytes — The Key Difference
ISPs advertise speeds in bits per second (Mbps), but files are sized in bytes (MB, GB). Since 1 byte = 8 bits, a 100 Mbps connection downloads at a maximum of 12.5 MB/s — not 100 MB/s.
| Unit | Full Name | Equal To | Used For |
|---|---|---|---|
| Mbps | Megabits/sec | 1,000 Kbps | Internet speed advertising |
| MB/s | Megabytes/sec | 8 Mbps | Download manager display |
| Gbps | Gigabits/sec | 1,000 Mbps | Enterprise, fiber |
| GB/s | Gigabytes/sec | 8 Gbps | SSD, PCIe, RAM |
Download Time Formula
Time (seconds) = File Size (MB) × 8 ÷ Speed (Mbps)
Example: 4.7 GB on 50 Mbps = (4,700 × 8) ÷ 50 = 752 sec ≈ 12.5 min
Add 10–20% for TCP/IP overhead in real-world conditions.
Streaming Bandwidth Requirements
| Quality | Resolution | Minimum | Recommended |
|---|---|---|---|
| SD | 480p | 1.5 Mbps | 3 Mbps |
| HD | 720p | 3 Mbps | 5 Mbps |
| Full HD | 1080p | 5 Mbps | 10 Mbps |
| 4K Ultra HD | 2160p | 15 Mbps | 25 Mbps |
| Video Call (Zoom) | 720p | 1.5 Mbps ↑↓ | 3 Mbps ↑↓ |
| Online Gaming | — | 3 Mbps | 15+ Mbps |
Frequently Asked Questions
Why is my download speed slower than advertised?â–¼
ISPs advertise 'up to' maximum speeds. Real speeds are reduced by Wi-Fi signal loss (20–50%), network congestion during peak hours, protocol overhead (5–15%), and server-side throttling.
What is the difference between bandwidth and throughput?â–¼
Bandwidth is the theoretical maximum capacity of your connection. Throughput is the actual data successfully transferred per second — always less than bandwidth due to overhead and congestion.
How much bandwidth does a website need?â–¼
Estimate: Monthly Bandwidth = Page Views × Average Page Size × 1.5. Example: 50,000 views × 3 MB × 1.5 = 225 GB/month.
What is latency and how is it different from bandwidth?â–¼
Latency is the round-trip delay (ms) for data to reach a server and return. High bandwidth + high latency = fast downloads but laggy real-time apps. For gaming and calls, low latency matters more.