Block to Megabyte

Modern hard drives (2011+) and SSDs use 4,096-byte (4 KiB) physical sectors — known as "Advanced Format" or AF. Legacy drives used 512-byte sectors. Filesystems (NTFS, ext4, APFS) typically use 4 KiB logical block sizes to match physical sectors, which avoids the performance penalty of misaligned writes. Enterprise SSDs may use larger block sizes (16 KiB or more) for better parallelism.

Cloud block storage services (AWS EBS, Azure Managed Disks, GCP Persistent Disk) use I/O block sizes typically of 4 KiB or 16 KiB. Performance is measured in IOPS (I/O operations per second) and throughput (MB/s) — both depend on block size. A throughput-optimized workload (sequential video) benefits from large blocks; an IOPS-optimized workload (database random reads) uses small blocks.

Filesystems allocate disk space in whole blocks. On a system with 4 KiB blocks, every file — no matter how small — occupies at least 4,096 bytes. A directory of 10,000 small configuration files (each 100 bytes of content) uses 40 MB of disk space (10,000 × 4,096 bytes) rather than 1 MB (10,000 × 100 bytes). This is called "block slack" or "internal fragmentation".

Disk blocks (filesystem blocks) are typically 512 bytes to 4 KiB. Database blocks (database pages) are the unit of I/O for a database engine — typically 8 KiB (PostgreSQL, SQL Server), 16 KiB (MySQL InnoDB), or 32 KiB (Oracle, configurable). Database blocks usually align to multiples of disk blocks for efficiency. Reading one database page may involve reading 2–8 disk blocks.

RAID stripe size (or chunk size) is the amount of data written to each drive before moving to the next drive in the array — typically 64 KiB to 512 KiB. It should be set to match your workload: sequential large-file workloads benefit from larger stripe sizes; random small-block workloads benefit from stripe sizes closer to the filesystem block size. Mismatched stripe and block sizes cause write amplification and reduce RAID performance.

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.