ISPs advertise in Mbps, downloads show MB/s. A 100 Mbps plan gives you just 12.5 MB/s. See the real number instantly.

Internet speeds are advertised in megabits per second (Mbps), but file sizes and download speeds are typically shown in megabytes per second (MB/s). 1 byte = 8 bits, so 1 MB/s = 8 Mbps.
This means a "100 Mbps" connection downloads at a maximum of 12.5 MB/s. A "1 Gbps" connection = 125 MB/s.
This conversion is essential for estimating download times, choosing an internet plan, and understanding the difference between advertised and actual speeds.
All calculations run locally in your browser — nothing is sent to any server.
1 byte = 8 bits. Therefore: Mbps ÷ 8 = MB/s, and MB/s × 8 = Mbps.
Example: 200 Mbps ÷ 8 = 25 MB/s. This is the theoretical maximum download speed.
Actual speeds are typically 70–90% of the advertised maximum due to protocol overhead, network congestion, and other factors.
| Feature | Megabit/s (Mbps) | Megabyte/s (MB/s) |
|---|---|---|
| Unit | Bits | Bytes |
| Ratio | 8 Mbps | = 1 MB/s |
| Used for | ISP speeds, bandwidth | File downloads, transfers |
| 100 Mbps | 100 Mbps | 12.5 MB/s |
| 1 Gbps | 1,000 Mbps | 125 MB/s |
100 Mbps = 12.5 MB/s. Divide by 8 because 1 byte = 8 bits. Most US ISP plans (Comcast 100 Mbps tier, AT&T Basic Fiber) give you exactly this theoretical maximum.
ISPs advertise in Mbps (bits), but your download manager shows MB/s (bytes). 100 Mbps = max 12.5 MB/s. Real-world speed is typically 70–90% of that due to protocol overhead, Wi-Fi interference, and server limitations.
1 GB = 1,000 MB. At 12.5 MB/s (100 Mbps): 1,000 ÷ 12.5 = 80 seconds theoretically. Realistically 90–120 seconds with overhead.
Netflix 4K Ultra HD requires 25 Mbps (3.1 MB/s). YouTube 4K needs 20 Mbps (2.5 MB/s). Disney+ 4K requires 25 Mbps. For a household with two 4K streams, plan for at least 50 Mbps.
Comcast's top residential plan is 1,200 Mbps (1.2 Gbps) download = 150 MB/s. Upload is typically 35 Mbps (4.4 MB/s) on cable. AT&T Fiber 5 Gbps is symmetrical — 625 MB/s both up and down.
A VPN adds 10–15% overhead for encryption (WireGuard) or up to 20% for older OpenVPN. On a 100 Mbps connection you can expect 85–90 Mbps effective throughput — about 10.6–11.3 MB/s instead of 12.5 MB/s.
AWS S3 multipart upload with a 100 Mbps uplink achieves roughly 10–12 MB/s in practice. For large dataset transfers (100 GB+), consider AWS Direct Connect or Snowball for speeds above your ISP limit.
Yes. All calculations run in your browser. No data is sent to any server.

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