Generates a QR code for the given text, returned as a base64-encoded PNG data URL, computed entirely locally with no external service call.

Tests a regular expression pattern against a string, guarded against catastrophic backtracking (ReDoS) by running the match in an isolated worker thread with a hard 500ms timeout that fails closed.

Rental property investment calculator. Full multi-year deal analysis for a rental property deal: mortgage, per-category rent/expense growth, a sale scenario, IRR, and cumulative totals over the holding period, alongside the first-year NOI/cap-rate/cash-on-cash snapshot.

Savings rate calculator. Divides the gap between monthly take-home income and spending by income to produce your personal savings rate as a percentage.

Compares two semantic version strings and reports which is greater, lesser, or equal, using the standard semver comparison rules.

Solves a system of linear equations (Ax = b) using the ml-matrix library's LU decomposition (LuDecomposition), with a near-singularity guard beyond the library's exact-singular check, for systems up to 20x20.

Descriptive statistics summary (mean, median, variance, standard deviation, and 25th/75th/90th percentiles via linear interpolation, matching R and numpy's default "type=7" method) over a numeric array of up to 10,000 elements.

Tesla savings calculator. Compares annual electricity cost for a Tesla 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.

Unit conversion for length, mass, volume, and temperature using exact conversion factors (temperature uses the correct affine formulas, not simple multiplication).

Scientific unit conversion for pressure, energy, and molarity using exact conversion factors.

Upwork freelancer fee calculator. Applies a documented tiered marginal service-fee schedule (20%/10%/5% at $500/$10,000 cumulative per-client lifetime billing thresholds) to compute take-home pay on an invoice, correctly splitting fees across a tier boundary like a tax bracket. Platform fee policies can change; verify current rates before relying on this for financial decisions.

URL decoder API. Decodes percent-encoded URL text back to plain text.

URL encoder API. Percent-encodes text for safe use in a URL query string or path segment, handling reserved-character rules LLMs often get wrong by hand.

Windfall impact on FIRE timeline calculator. Runs the FIRE net-worth simulation twice — with and without a one-time lump sum added at a given year — and reports how many years the windfall shaves off your time to financial independence.