Petabit to Megabyte

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.

A JPEG photo from a modern smartphone is typically 3–8 MB depending on resolution and compression settings. A RAW format photo from a DSLR or mirrorless camera is 20–50 MB per shot. A PNG screenshot at full HD (1920×1080) is about 1–3 MB; a compressed JPEG screenshot may be under 200 kB.

Video data usage depends heavily on quality: SD video uses roughly 700 MB per hour; HD (1080p) uses 1.5–3 GB per hour; 4K uses 7–20 GB per hour. These are byte-based measurements. In terms of bitrate: SD ≈ 1.5 Mbps, HD ≈ 5–8 Mbps, 4K ≈ 15–25 Mbps — where the "b" is bits, requiring division by 8 to convert to MB/s.

Compression algorithms like ZIP, GZIP, and ZSTD find and eliminate redundancy in data. Typical ratios vary dramatically by file type: plain text compresses to 20–30% of original size (a 10 MB log file becomes 2–3 MB); source code compresses to 25–35%; office documents (DOCX, XLSX) are already ZIP-compressed internally, so re-compressing gains little. JPEG, MP3, and H.264 video are already lossy-compressed and typically shrink by less than 5% with ZIP. A 100 MB folder of mixed files typically compresses to 40–60 MB. The key principle: compression removes statistical redundancy, so already-compressed or random data cannot be reduced further.

MB (megabyte) = 1,000,000 bytes (SI decimal). MiB (mebibyte) = 1,048,576 bytes (IEC binary). The difference is about 4.9%. Windows historically displayed storage in binary units but labelled them as "MB" — confusingly. Since Windows Vista, Microsoft has used the binary calculation consistently. macOS switched to SI decimal units in OS X 10.6 Snow Leopard (2009), matching the way hard drive manufacturers measure capacity.

Approximate data consumption per hour: web browsing = 60–100 MB, social media scrolling = 100–300 MB, music streaming (Spotify standard) = 40–50 MB, video calls (Zoom standard quality) = 300–500 MB, YouTube HD = 1,500–3,000 MB. These are rough averages and vary by content, settings, and network conditions.