Alcohol spending and opportunity-cost calculator. Sums home and going-out drinking costs plus associated rideshare costs into monthly and yearly totals, then projects what that redirected spending could grow into if invested instead, using the future-value-of-an-annuity formula.

Sunrise, sunset, solar noon, day length, and moon phase for a given latitude/longitude/date, computed via the suncalc library (standard solar/lunar position algorithms) — precise astronomical math an LLM cannot reliably compute mentally.

Barista FIRE calculator. Simulates net worth growth through a full-time-saving phase and then a reduced-target phase funded partly by part-time/side income after quitting full-time work, until full financial independence is reached.

Base64 decoder API. Decodes a base64 string back to UTF-8 text instantly and correctly, avoiding the padding and charset errors LLMs make when decoding base64 by hand.

Base64 encoder API. Encodes UTF-8 text to base64 instantly and correctly — skip burning agent tokens hand-computing base64, which LLMs frequently get wrong on padding and edge cases.

Arbitrary-precision integer arithmetic (add, subtract, multiply, power) beyond IEEE-754 float precision, using native BigInt. Operands are passed as digit strings so precision is never lost in transit. For power, the combined magnitude (base digit count x exponent) is capped at 50000 to bound response size, in addition to the per-operand digit cap and exponent cap.

Cap rate calculator for real estate investing. Runs a full multi-year deal analysis (per-category rent/expense growth, a sale scenario, IRR) and headlines the capitalization rate: first-year NOI divided by purchase price.

Cash-on-cash return calculator for real estate investing. Runs a full multi-year deal analysis (per-category rent/expense growth, a sale scenario, IRR) and headlines the first-year cash-on-cash return: operating cash flow divided by invested cash.

Periodic table element lookup by symbol or atomic number, returning name, atomic mass, and category. Covers the most commonly referenced elements.

Coast FIRE calculator. Computes the lump sum needed today, invested with zero further contributions, to grow into your full retirement number by your target retirement age, plus (given an ongoing monthly contribution) a year-by-year projection of when your actual trajectory crosses that lump sum.

Converts a color between hex, rgb, and hsl representations using exact arithmetic.

Compound interest calculator. Projects the ending value of an investment given a starting principal, monthly contributions, and an annual interest rate, compounded monthly over a chosen number of years.

Computes the next N run times for a standard 5-field cron expression, avoiding the mental cron-schedule simulation an LLM often gets subtly wrong.

Line-based diff between two strings using the Myers diff algorithm (via the diff/jsdiff library), returning a list of equal/add/remove operations.

Electric car savings calculator. Compares annual electricity cost against annual gas cost for a comparable gas vehicle, accounting for free-charging usage, and computes break-even years, cost per full charge, and gas-price-equivalent effective MPG.

Emergency fund calculator. Multiplies monthly essential expenses by a chosen runway length (in months) to compute a target emergency savings amount.

Safe arithmetic expression evaluator. Parses and evaluates expressions with +, -, *, /, ^, and parentheses using a bounded-recursion parser (no eval/Function), avoiding the arithmetic slips an LLM makes on long expressions.

Fat FIRE calculator. Same year-by-year compound-growth simulation as the standard FIRE calculator, framed for a higher, more lifestyle-preserving retirement spending target.

FIRE (Financial Independence, Retire Early) calculator. Projects year-by-year net worth growth to determine how many years until your portfolio can sustainably fund retirement spending at a given safe withdrawal rate — precise compound-growth simulation an LLM cannot reliably run mentally. incomeGrowthRate is deflated by inflationRate internally. Past retirementAge the simulation draws down retirementAnnualSpending with no further income.

Gas mileage savings calculator. Compares annual fuel cost between two gas-powered vehicles based on miles driven, gas price, and each vehicle's MPG, and computes the break-even point for any price premium of the more efficient vehicle.

Checksummed-identifier-format generator API. Generates a structurally valid isbn, upc, vin, or imei, each computed with its real check-digit algorithm. vin and imei take no arguments. Accepts optional locale (default en_US).

True-random-date generator API. Generates a bounded random date via one of: anytime, past, future, between, betweens, recent, soon, birthdate. between/betweens require "from" and "to" date strings. Accepts optional locale (default en_US). Date args must parse to a valid date with year 1000-9999.

Checksummed-financial-identifier generator API. Generates a structurally valid iban, bic, creditCardNumber, bitcoinAddress, litecoinAddress, ethereumAddress, or routingNumber, each computed with its real checksum algorithm (mod-97, Luhn, EIP-55, etc.). Accepts optional locale (default en_US).

True-random-geo-coordinate generator API. Generates a bounded random latitude, longitude, or a coordinate near a given origin (via one of: latitude, longitude, nearbyGPSCoordinate). Accepts optional locale (default en_US). Numeric args are capped to +/-1e15; precision is capped to 0-20; origin must be a [latitude, longitude] pair.

Network-format generator API. Generates a valid ipv4/ipv6 address (optionally within a CIDR block or named network range) or a well-formed JWT string (via one of: ipv4, ipv6, jwt). Accepts optional locale (default en_US). jwt header/payload objects are capped to 2000 serialized characters.

True-random-number generator API. Generates a bounded random number via one of: int, float, binary, octal, hex, bigInt (returned as a string), romanNumeral. Accepts optional locale (default en_US). Numeric args (min, max, multipleOf) are capped to +/-1e15; fractionDigits is capped to 0-20.

Secure password generator API. Generates a cryptographically random password — true randomness an LLM cannot produce on its own. Accepts optional length (8-128), per-character-class toggles (uppercase/lowercase/numbers/symbols) with guaranteed inclusion, and a pronounceable easy-to-say mode.

Slug generator API. Converts any text into a clean, URL-safe slug (lowercase, hyphen-separated, unicode-aware), handling punctuation and accented-character edge cases a naive regex misses.

True-random-string generator API. Generates a bounded random string via one of: alpha, alphanumeric, binary, octal, hexadecimal, numeric, sample, uuid, ulid, nanoid, symbol. Accepts optional locale (default en_US). length/count-style args are capped to 0-1000.

UUID generator API. Generates a random RFC 4122 version 4 UUID using a cryptographically secure source — not the pseudo-random, collision-prone IDs an LLM would invent. No input required.

Live currency exchange rate API. Returns the current exchange rate between any two ISO 4217 currency codes (e.g. USD to EUR) — live external data an LLM cannot know on its own.

Live cryptocurrency price API. Returns the current market price (in USD) of any cryptocurrency by ticker symbol (BTC, ETH, DOGE, etc.) — live market data an LLM cannot know on its own.

Live weather API. Returns real-time weather conditions, temperature, feels-like temperature, humidity, wind speed, precipitation, and UV index for any city worldwide — live external data an LLM cannot know on its own. Supports metric/imperial units, 74 languages, and optional 3-day forecast and sun/moon astronomy data.

MD5 hash generator API. Computes the MD5 hex digest of any text. Deterministic and instant — an LLM cannot reliably compute real cryptographic hashes on its own.

SHA-256 hash generator API. Computes the SHA-256 hex digest of any text. Deterministic and instant — an LLM cannot reliably compute real cryptographic hashes on its own.

House hacking calculator. Nets rental income from other units/rooms against your mortgage payment and expenses, then adds back the equity you build via principal paydown and the market rent you avoid paying elsewhere, to compute the true monthly net-worth impact of living in and renting out part of a property.

HSA (Health Savings Account) growth calculator. Projects year-by-year account balance from a starting value, annual contributions, annual expense withdrawals, and an annual return rate.

Hybrid vs gas savings calculator. Compares annual fuel cost between a hybrid and a conventional gas vehicle based on miles driven, gas price, and each vehicle's MPG, and computes the break-even point for the hybrid's price premium.

Email validation API. Checks whether a string is a syntactically valid email address using the same production-grade validation library trusted across the Node.js ecosystem, catching edge cases a quick regex misses. Returns true or false.

Deterministic primality test using the Miller-Rabin algorithm with a witness set proven deterministic for all integers below 3.3x10^24, safely covering the full JavaScript safe-integer range.

URL validation API. Checks whether a string is a syntactically valid URL, catching malformed schemes, hosts, and encoding edge cases a naive check misses. Returns true or false.

Decodes (does not verify) a JWT by base64url-decoding its header and payload segments. Signature validity is never checked — do not use this to authenticate a token.

Keeping up with inflation calculator. Computes the pre-tax raise needed under two scenarios — keeping the same dollar amount saved, or maintaining the same savings rate — after inflation raises your spending and a marginal tax rate reduces the raise itself.

Loan payment calculator. Computes the fixed monthly payment for a standard amortizing loan and returns the full month-by-month principal/interest/balance schedule — exact amortization math an LLM cannot reliably compute by hand for hundreds of periods.

Matrix operations: multiply, transpose, determinant, and invert, for matrices up to 20x20. Uses the ml-matrix library's LU decomposition (LuDecomposition) for determinant and inversion, with a numerical near-singularity guard beyond the library's exact-singular check.

15-year vs 30-year mortgage comparison calculator. Computes monthly payment and total interest for both loan terms on the same purchase price and down payment, and reports the payment and lifetime-interest tradeoff between them.

Lookup of standard physical constants (speed of light, gravitational constant, Planck constant, elementary charge, Avogadro number, Boltzmann constant, gas constant, electron mass) with exact published CODATA values.

Portfolio rebalancing calculator. Given current holdings and target allocation percentages, computes the dollar gap per asset and the monthly buy/sell inflow needed to reach the target allocation over a chosen rebalancing period.

Prime factorization of an integer via trial division, returning the full list of prime factors (with repetition).

Purchase impact on FIRE timeline calculator. Runs the FIRE net-worth simulation twice — with and without a one-time purchase amount deducted at a given year — and reports how many years that purchase delays financial independence, quantifying its true opportunity cost.