Tools for Founder

21 hand-picked tools for Founder. Free, private, browser-based.

AI Eval Planner

Generate eval cases, pass criteria, and edge cases from an AI feature, risks, and user path.
Break-Even Calculator

How many units must you sell to stop losing money? Enter fixed costs, price, and variable cost per unit for break-even units, break-even revenue, and contribution margin — browser-only
Commission Calculator

Work out sales commission three ways — flat rate, progressive tiers, or reverse-solve the sales you need to hit an income target. Browser-only, shareable.
CSP Policy Auditor

Inspect Content-Security-Policy directives for unsafe sources, missing fallbacks, framing gaps, object-src, base-uri, and reporting coverage.
Date Difference Calculator

Days / weeks / months / years between two dates — plus business-days mode — browser-only
ENV Secret Scanner

Scan .env files, config snippets, and CI logs locally for likely API keys, tokens, private keys, JWTs, and database URLs.
Freelance Hourly Rate Calculator

Back into the hourly rate you must charge from your target salary, business expenses, billable hours, profit margin, and taxes — browser-only
HAR Performance Analyzer

Upload a Chrome DevTools HAR file and get a local performance, cache, host, asset, status, and security-header report.
HTTP Security Header Auditor

Audit raw response headers for HSTS, CSP, cookie flags, MIME sniffing, clickjacking, referrer, and permissions policy gaps.
LLM Pricing Calculator

Estimate daily and monthly LLM spend from tokens, request volume, and editable model prices.
Log Error Analyzer

Paste logs and group repeated errors, warnings, stack traces, HTTP statuses, endpoint patterns, and time ranges into a local incident report.
Markup & Margin Calculator

Cost ⇄ price ⇄ markup % ⇄ margin % — solve any two, see both rates side by side — 100% in your browser
OpenAPI Endpoint Auditor

Audit OpenAPI JSON or YAML for endpoint coverage, missing operation IDs, security gaps, and weak response documentation.
Package Lock Dependency Auditor

Inspect package-lock.json, pnpm-lock.yaml, or yarn.lock for duplicate versions, risky sources, prereleases, and missing integrity.
Percentage Calculator

5 common percentage calculations — "x% of y", "x is what% of y", percentage change, increase/decrease — instant, browser-only
Random Number Generator

Generate cryptographically-secure random integers — single or batch, with/without duplicates — browser-only
Rent vs Buy Calculator

See whether buying beats renting and investing the difference — net cost, terminal equity, and the break-even year, all in your browser
Robots.txt Auditor

Check robots.txt for user-agent groups, allow and disallow rules, sitemap declarations, crawl-delay, and unsupported directives.
Sales Tax Calculator

Add or remove US sales tax — split state + local rates, real 2024 state base rates on tap, browser-only
Timezone Converter

Convert any time between any two timezones — DST-aware, IANA database — browser-only
Unit Converter

Convert between length, weight, temperature, area, volume, speed, time — instant, browser-only