# Developer & IT calculators

> IPv4 subnetting, bitwise and two's-complement arithmetic, IEEE-754 floats, cron schedules, Unix permissions, hashes, Base64 size, string similarity, LLM memory and token cost, bandwidth-delay product, audio file size, CSS units, semantic versions, colour contrast.

15 calculators. HTML index: https://tttkmbb.com/developer · JSON: https://tttkmbb.com/api/v1/calculators?category=developer

- [IP Subnet Calculator](https://tttkmbb.com/developer/subnet-calculator.md): Computes the network and broadcast addresses, subnet and wildcard masks, first and last host, usable and total addresses, address class and RFC 1918 private status for an IPv4 address in CIDR notation or with a dotted subnet mask, using 32-bit unsigned arithmetic. Tool: `calculate_subnet`.
- [Bitwise Operations Calculator](https://tttkmbb.com/developer/bitwise-operations.md): Applies AND, OR, XOR, NOT, left shift, logical right shift or arithmetic right shift to integers of a chosen width (8, 16 or 32 bits) and reports the result as signed two's complement, unsigned, binary and hexadecimal. Tool: `calculate_bitwise_operations`.
- [IEEE 754 Floating-Point Converter](https://tttkmbb.com/developer/ieee-754-float.md): Encodes a decimal number as an IEEE 754 binary32 (single) or binary64 (double) value and reports the sign, exponent and mantissa bit fields, the hexadecimal and binary representation, the exact value actually stored and the rounding error. Tool: `convert_ieee_754_float`.
- [Cron Schedule Calculator](https://tttkmbb.com/developer/cron-schedule.md): Parses a standard 5-field crontab expression (minute, hour, day of month, month, day of week with *, lists, ranges, steps and names) and lists the next run times in UTC after a start date and time, with a plain-English summary of the schedule. Tool: `calculate_cron_schedule`.
- [Unix Permissions Calculator](https://tttkmbb.com/developer/unix-permissions.md): Converts a Unix/Linux file mode between octal (755, 0644, 4755) and symbolic (rwxr-xr-x, -rw-r--r--, u=rwx,g=rx,o=rx) notation and explains the read/write/execute bits for owner, group and others plus the setuid, setgid and sticky bits. Tool: `convert_unix_permissions`.
- [Text Hash Calculator](https://tttkmbb.com/developer/text-hash.md): Computes the MD5 (RFC 1321), SHA-1 (RFC 3174), SHA-256 (FIPS 180-4) and CRC-32 (IEEE 802.3 polynomial) digests of a text encoded as UTF-8, plus its byte length; all algorithms are implemented in plain JavaScript. Tool: `calculate_text_hash`.
- [Base64 Size Calculator](https://tttkmbb.com/developer/base64-size.md): Computes the length of the Base64 encoding of a given number of bytes (4 characters per 3 bytes, padded with =), the 33 % overhead, the size with MIME/PEM line breaks and the length of a data: URI. Tool: `calculate_base64_size`.
- [String Similarity Calculator](https://tttkmbb.com/developer/string-similarity.md): Compares two strings with the Levenshtein edit distance and similarity, Jaro and Jaro–Winkler similarity, the bigram Sørensen–Dice coefficient, the Hamming distance (equal lengths only) and the longest common subsequence length. Tool: `calculate_string_similarity`.
- [LLM VRAM Calculator](https://tttkmbb.com/developer/llm-vram-estimate.md): Estimates the GPU memory needed to run a transformer language model for inference from its parameter count and bits per weight (weights), layer count, hidden size, context length and batch size (KV cache), plus a percentage overhead for activations and the CUDA context, and lists which common GPU sizes it fits. Tool: `estimate_llm_vram`.
- [LLM Token Cost Calculator](https://tttkmbb.com/developer/llm-token-cost.md): Computes the cost of large-language-model API calls from the number of input, cached-input and output tokens per request, the prices per million tokens supplied by the caller, and the number of requests. Tool: `calculate_llm_token_cost`.
- [Bandwidth-Delay Product Calculator](https://tttkmbb.com/developer/bandwidth-delay-product.md): Computes the bandwidth-delay product (bits in flight) of a network path from its bandwidth and round-trip time, the TCP receive window needed to fill it, and the throughput a given window size can achieve. Tool: `calculate_bandwidth_delay_product`.
- [Audio File Size Calculator](https://tttkmbb.com/developer/audio-file-size.md): Computes the size of an audio recording from its duration and either the PCM parameters (sample rate × bit depth × channels, as in WAV/AIFF/CD audio) or a constant compressed bitrate (MP3, AAC, Opus), in bytes, MB and MiB, plus the minutes that fit in one gigabyte. Tool: `calculate_audio_file_size`.
- [CSS Unit Converter](https://tttkmbb.com/developer/css-units.md): Converts a CSS length between px, rem, em, pt, pc, in, cm, mm and Q using the CSS reference pixel (96 px per inch, 1 pt = 1/72 in) and the root and parent font sizes for rem and em, and lists the value in every unit. Tool: `convert_css_units`.
- [Semantic Version Comparator](https://tttkmbb.com/developer/semver-compare.md): Parses two Semantic Versioning 2.0.0 strings, orders them by the specification's precedence rules (numeric core, then pre-release identifiers; build metadata ignored) and reports whether the second version satisfies the npm-style ^ (caret) and ~ (tilde) ranges of the first. Tool: `compare_semver_versions`.
- [Colour Contrast Checker](https://tttkmbb.com/developer/color-contrast.md): Computes the WCAG 2.1 contrast ratio between a foreground and a background colour from their relative luminance (sRGB linearised) and checks it against the AA and AAA thresholds for normal text, large text and non-text UI components. Tool: `calculate_color_contrast`.