MODOO — Free Browser-Based Tools

About MODOO

MODOO is a collection of small, focused tools that run entirely in your browser. Every calculator and editor on this site is a single static HTML page — no sign-up, no account, no data uploaded anywhere.

The site is built and hosted on Cloudflare Pages' free tier. Because computation happens locally, there are no server costs and nothing about your inputs ever leaves your device. Results disappear when you close the tab unless a specific tool offers local-only storage.

How to Use This Page

• Browse the tool cards above and click one to open it.
• Search by name or description. Press / or Ctrl+K (⌘K on Mac) to jump to the search box.

Available Tools

• PRD Editor — write product requirements documents in Markdown with a live, editable preview. Supports tables, task lists, code blocks with syntax highlighting, and Mermaid diagrams.
• Interest Calculator — savings, recurring deposits, loans (amortizing / equal-principal / interest-only), and simple vs. compound comparisons.
• Salary Calculator — estimate U.S. take-home pay using 2024 federal brackets, a user-supplied state rate, FICA, and pre-tax deductions.
• Retirement Calculator — project a nest egg to retirement, check how long savings last in drawdown, solve for the monthly contribution that hits a goal, and stress-test a safe withdrawal rate.
• Mortgage Calculator — full PITI monthly payment with taxes, insurance, HOA, and PMI; year-by-year amortization (with optional extra payments); affordability check from income; refinance break-even.
• Investment Calculator — future value of lump-sum + periodic contributions, required-return solver, time-to-goal solver, and side-by-side scenario comparison.
• Sales Tax Calculator — add tax to a price, reverse-extract tax from a total, sum a multi-item invoice, and look up state base sales tax rates.
• BMI Calculator — Body Mass Index in metric or imperial units, healthy weight range, US-Navy body fat estimate, and ideal-weight formula comparison.
• Tip Calculator — compute a tip, split a bill across people, reverse-engineer the pre-tip amount, or round up to a clean total.
• Percentage Calculator — four common percentage operations: X% of Y, A is what % of B, percent change, and reverse markup/markdown.
• Pregnancy Calculator — due date from LMP/conception/IVF, current gestational week, and milestone schedule.
• Debt Payoff Calculator — multi-debt schedule using snowball or avalanche; side-by-side comparison and extra-payment impact.
• Time Zone Converter — world clock for multiple cities, convert a specific moment across zones, and a 24-hour meeting-planner grid.
• Calorie & TDEE Calculator — BMR (Mifflin-St Jeor / Harris-Benedict / Katch-McArdle), TDEE by activity level, calorie targets for several goals, and a macro split.
• Income Tax Calculator — 2024 U.S. federal brackets with standard or itemized deduction, self-employment tax (Schedule SE), capital gains, and refund/owed snapshot.
• Inflation Calculator — convert dollars between any two years using BLS CPI-U (1913–2024), project future purchasing power, and view CPI history.
• Unit Converter — length, weight, temperature, area, volume, speed, time, and data units (decimal & binary).
• Age & Date Calculator — exact age in years/months/days, difference between any two dates, date arithmetic, and weekday counts.
• Scientific Calculator — full scientific calculator with trig (degrees/radians), logs, factorials, parentheses; programmer mode (DEC/HEX/OCT/BIN, bitwise); equation solver for linear, quadratic, and cubic polynomials.
• JSON Formatter — beautify, minify, validate (with error location), and explore JSON as an expandable tree.
• Word Counter — words, characters, sentences, paragraphs, reading/speaking time, and keyword density analysis.
• Pomodoro Timer — 25/5 focus sessions with audio and browser notifications, daily stats, customizable durations.
• QR Code Generator — URLs, Wi-Fi credentials, vCard contacts, email/SMS; PNG and SVG download.
• Base64 Converter — UTF-8 safe encode/decode plus File-to-Data-URI conversion; URL-safe variant supported.
• URL Encoder/Decoder — percent-encode/decode with encodeURI vs encodeURIComponent, plus full URL parsing with query parameters.
• Regex Tester — live JavaScript regex match highlighting, capture groups, replace, and a library of common patterns.
• UUID Generator — cryptographic v4 UUIDs, bulk up to 1000, and decode existing UUIDs to inspect version and timestamp.
• To-Do List — daily tasks with priorities, filters, and inline editing; everything stored in your browser.
• Habit Tracker — daily check-ins, streak counting, and a GitHub-style 12-week heatmap.
• Stopwatch & Timer — millisecond-precision stopwatch with laps, and a countdown timer with audio alarm.
• Random Picker — pick from a list, generate random numbers, flip coins, roll polyhedral dice, and shuffle lists. Cryptographically random.

Privacy & Data

MODOO does not run a backend. We have no analytics, no cookies for tracking, and no way to see what you type. The only data stored locally is optional per-tool defaults that a tool may save in your browser. You can wipe everything by clearing site data in your browser. External scripts loaded from cdn.jsdelivr.net (used by the PRD Editor for Markdown rendering) are subject to that CDN's privacy policy.

Frequently Asked Questions

Is MODOO free?

Yes — completely free with no sign-up. The hosting cost is covered by Cloudflare Pages' free tier.

Can I trust the calculator results?

Each tool is a planning aid, not a contract or official advice. Tax tools follow published government rates and brackets but cannot capture every credit, deduction, or local rule. For binding decisions, consult a professional or the official source.

Is a Korean version available?

Yes — visit modoo.example.kr for the Korean edition. The Korean Salary Calculator uses Korean four-major-insurance and income-tax brackets instead of U.S. tax logic.

Can I suggest a new tool?

Candidate pool includes an auto-loan calculator, tip calculator, income-tax calculator, BMI & calorie calculators, annual-leave calculator, hourly-time tracker, and a bill-splitting calculator. New tools are added when there's a clear use case and the math fits a browser-only model.

References

• Cloudflare Pages — free static-site hosting. pages.cloudflare.com
• CommonMark specification (used by the PRD Editor). commonmark.org
• Mermaid diagram syntax. mermaid.js.org

Educational content on this page is original prose written for MODOO. Material referenced from Wikipedia (linked inside individual tools) is used under the CC BY-SA 4.0 license.