Mbps vs. MB/s: Why Your 100 Mbps Internet Only Downloads at 12.5 MB/s

The number on your internet bill — 300 Mbps, 500 Mbps, 1 Gig — measures throughput in megabits per second. The number you watch when a game downloads or a 4K movie saves to your drive appears in megabytes per second. They differ by a factor of eight, and the confusion costs consumers money and time.

A megabit is one million binary digits. A megabyte is eight million of them — eight bits to a byte, the standard unit that represents a single character of text. Internet service providers have advertised in bits since the dial-up era because the numbers look bigger. Storage manufacturers, cloud services, and operating systems report in bytes because that matches how files are actually sized.

The Federal Communications Commission raised its broadband benchmark to 100 Mbps down and 20 Mbps up in 2024, quadrupling the 2015 standard of 25/3. Ookla’s Speedtest Intelligence put the U.S. median at 307 Mbps down and 63 Mbps up as of August 2026. But a 300 Mbps plan delivers roughly 37.5 MB/s in ideal conditions — enough to pull a 50 GB game in about 22 minutes, assuming no overhead, no congestion, and a wired connection.

Real-world throughput rarely matches the marketed rate. Wi-Fi 6E and Wi-Fi 7 routers can sustain multi-gigabit links locally, but interference, distance, and device limitations shave 30 to 50 percent off the wired headline speed. Ethernet remains the only way to see the full provisioned rate. Meanwhile, latency — the round-trip time for a single packet — matters more than raw bandwidth for video calls and gaming, yet it rarely appears in marketing.

Data caps reintroduce the bits-versus-bytes trap. A 1.2 terabyte monthly cap equals 1,200,000 megabytes, or 9.6 trillion bits. Streaming 4K HDR at 25 Mbps consumes about 11.25 GB per hour; a household hitting the cap would need roughly 107 hours of peak-quality viewing. Providers count against the cap in bytes, but sell the tier in bits.

Cloud backup and sync services — Backblaze, Dropbox, OneDrive — report upload speeds in MB/s. On a 20 Mbps upstream plan, the theoretical ceiling is 2.5 MB/s. Encryption overhead and protocol chatter typically cut that to 1.8–2.0 MB/s. A 200 GB initial backup would take 28 to 31 hours of uninterrupted upload.

The conversion is immutable: divide megabits by eight for megabytes, multiply megabytes by eight for megabits. No firmware update, no router upgrade, and no negotiation with support can change it. The FCC’s next broadband review, expected in 2027, may incorporate latency and consistency metrics alongside the bits-based speed floor.