Deterministic arithmetic for systems and network work: subnets, RAID capacity, transfer time, bitrate and file size, uptime, pixels, TCP throughput, backups.
The sums behind systems and network work, done exactly and shown in the open: how an IPv4 or IPv6 block splits into subnets; how much of a RAID array you can actually use and how many disks it survives; how long a transfer takes at a given speed; what a bitrate turns into on disk; what an availability figure allows in downtime; how a bandwidth-delay product limits TCP; what a backup schedule will consume. Decimal and binary units (MB and MiB) are never conflated — every page says which one it is using.
Usable capacity, overhead, efficiency and fault tolerance of a RAID 0, 1, 5, 6 or 10 array from disk count and size — in decimal TB as sold and TiB as shown.
You get: The usable space in TB and TiB, how much goes to redundancy, how many disks may fail, and every level compared at the same disks.
Open RAID CapacityFile size from bitrate and duration, the bitrate that fits a target size, or how long a card or disk records — video plus audio, GB and GiB both shown.
You get: The size of a recording or encode, the video bitrate a size budget allows after audio, the recording time a capacity gives, and the bytes per hour at that rate.
Open Video Bitrate & File SizeAspect ratio of any pixel size reduced to its simplest form, the nearest named ratio, megapixels, a proportional resize, and print size at a given dpi.
You get: The ratio as 16:9 and 1.7778:1, megapixels and orientation, the missing side when you resize, the print size in inches and cm, and common ratios at your width.
Open Aspect Ratio & PixelsStorage a full + incremental backup schedule needs for a retention window, from data size, daily change, full interval and your compression ratio, plus growth.
You get: The backup capacity now and after growth, what is written each week, and the number and size of fulls and incrementals kept — every rate yours, none assumed.
Open Backup Storage & RetentionDowntime allowed per day, week, month and year for an availability figure, the availability a measured outage gives, and the uptime of chained components.
You get: The permitted outage for any number of nines, an availability percent from downtime over a period, and the series or parallel availability of dependent services.
Open Uptime & SLAHow long a file takes at a given link speed, the speed needed to finish in time, or how much moves in a given time — bits and bytes, MB and MiB kept apart.
You get: The transfer time as hours, minutes and seconds, the payload rate in MB/s and MiB/s, and the same file on common link speeds side by side, with the overhead you enter.
Open Download & Transfer TimeIPv4 and IPv6 subnet from an address and prefix: network, broadcast, mask, wildcard, host range, usable hosts, binary view, and a split into smaller subnets.
You get: The network and broadcast addresses, first and last host, host count, mask and wildcard for any CIDR, the address in binary with the split marked, and the list of subnets when you carve it up.
Open Subnet CalculatorBytes in flight on a link from bandwidth and round-trip time, the TCP window that fills it, and the throughput one stream reaches with the window you have.
You get: The bandwidth-delay product in bytes and KiB, the window a single TCP connection needs, the throughput it gets with a given window, and the 64 KiB ceiling without window scaling.
Open Bandwidth-Delay Product