Megabit to Petabit

Divide Mbps by 8 to get megabytes per second (MB/s). A 100 Mbps connection = 12.5 MB/s. A 1 Gbps connection = 125 MB/s. This conversion is essential when comparing advertised internet speeds (always in Mbps) to actual file download speeds (shown in MB/s by browsers and download managers).

Netflix recommends 25 Mbps for 4K Ultra HD. Disney+ and Apple TV+ recommend 25 Mbps; YouTube recommends 20 Mbps for 4K. These are per-stream figures — a household streaming two 4K sources simultaneously needs roughly 50 Mbps of reliable throughput, plus headroom for other devices.

ISP speed ratings are theoretical maximums under ideal conditions. Real-world factors include network congestion, router quality, Wi-Fi interference, the server's upload speed, and protocol overhead. Additionally, browsers and download managers report speeds in MB/s (bytes), which is 8× smaller than the Mbps figure — a 100 Mbps plan showing 11 MB/s in a browser is performing normally.

One gigabit equals 1,000 megabits (SI decimal system). Gigabit broadband (1 Gbps) = 1,000 Mbps = 125 MB/s theoretical download speed. In the binary IEC system, one gibibit = 1,024 mebibits — but for internet speeds the SI decimal values are always used.

Fiber-to-the-home (FTTH) delivers symmetric speeds of 100–10,000 Mbps with consistent performance regardless of distance from the exchange. Cable (DOCSIS 3.1) offers 100–1,200 Mbps download but typically 10–50 Mbps upload, and throughput degrades during neighborhood peak hours due to shared bandwidth. DSL (VDSL2) maxes out at 50–100 Mbps download and drops sharply beyond 500 meters from the DSLAM cabinet. In practice, most cable users see 60–80% of advertised speeds; DSL users at distance may see under 50%. Fiber is the only technology that reliably delivers its rated megabit throughput.

One petabit = 10¹⁵ bits = 125 terabytes. To put it in perspective: the entire text content of all English Wikipedia articles is roughly 4 GB — so a petabit could hold about 31,000 copies of it. A petabit per second link could transfer all of Wikipedia's text content in about 32 microseconds.

As of 2024, no single commercial link carries 1 Pbps, but laboratory experiments have demonstrated fiber optic transmission exceeding 1 Pbps using dense wavelength-division multiplexing on a single fiber strand. Commercial submarine cables aggregate hundreds of terabits per second across many fibers and wavelengths, collectively reaching petabit-scale capacity per cable system.

A petabit (Pb) = 10¹⁵ bits. A petabyte (PB) = 10¹⁵ bytes = 8 petabits. Storage systems (data centers, archival systems) use petabytes for capacity; aggregate network throughput uses petabits per second. An exabyte-scale data center stores 1,000 petabytes; its internal network may carry multiple petabits per second of traffic.

Qubits and classical bits solve fundamentally different problems — qubits will not simply replace petabit-scale classical storage or networking. A quantum computer with 1,000 logical qubits can explore 2¹⁰⁰⁰ states simultaneously, but measuring those qubits collapses them to classical bits. Quantum networks will likely handle key distribution and entanglement sharing at kilobit-to-megabit rates, while classical infrastructure continues to move petabits of bulk data. The two technologies are complementary, not substitutional.

Submarine fiber optic cables are built by a handful of companies (SubCom, NEC, Alcatel Submarine Networks) and typically cost $200–500 million per system. A modern cable contains 12–24 fiber pairs, each carrying hundreds of wavelengths via dense wavelength-division multiplexing, reaching 400+ Tbps aggregate capacity per cable. Cables are designed to last 25 years on the ocean floor. When faults occur, specialised cable repair ships (fewer than 60 exist worldwide) locate breaks using optical time-domain reflectometry and splice repairs at sea — a process that can take days to weeks depending on depth and weather.