Free Developer & Code Tools & Calculators
Browse 326+ free interactive developer & code calculators, estimators, and utilities. 100% free, private, and runs directly in your browser without signup.
Putting Green Size Calculator — Backyard Golf Green Planner
Size a backyard putting green: green dimensions from your space, shape planner, turf takeoff, base and drainage, cups, slope advisor and DIY vs pro cost. 100% client-side.
Python Code Formatter
Python Code to Text Converter
Interactive converter that transforms Python source code into plain text explanations, pseudocode, and documentation.
Python JSON to CSV Converter
Convert JSON to CSV online and generate production-ready Python code using Pandas json_normalize and native csv modules.
Quartz to Cron — Convert Java Quartz Cron to Linux Cron
Convert Java Quartz cron expressions to Linux crontab online. Paste a 6- or 7-field Quartz expression, get the 5-field Linux cron with field mapping, validation and honest approximation warnings. Free, 100% client-side.
Query String Parser & URL Analyzer Studio
Interactive query string parser and urlparse javascript inspector for web developers, API engineers, and SEO specialists.
Random Animal Generator
Generate random animals, mythical beasts, and creature names.
Random Number Generator 1-50 & Lottery Suite
Precision random number generator 1-50, 1-100, lottery number generators, 3/4/6 digit code generator, and without replacement randomizer list.
Random Number Generator
Engineering-grade, cryptographic Random Number Generator, sequence chooser, digit code generator, and list selector.
Regex Extractor - Extract Text with Regex Online
Free online regex extractor: extract emails, URLs, phone numbers and dates from text with regular expressions. Dedupe, count, and export matches to CSV, JSON or plain lines. 100% client-side.
Regex Split
Split strings using regular expressions.
Regex Strip Special Characters & Pattern Tester
Free online regex tool, pattern matching tester, and generator. Strip special characters, test JavaScript and Python regex replace, and build URL regular expressions.
Regex Tester - Test & Debug Regular Expressions Online
Free online regex tester: test JavaScript regular expressions with live highlighting, flag toggles, capture-group breakdown, find & replace, and a plain-English pattern explainer. 100% client-side.
Regex URL Extractor & Hyperlink Scraper Tool
Standalone url regex, url scraper, hyperlink extractor, web text extractor, and extract url from text. Extract links from webpage, href extractor, regular expression to match url, and link scraper with zero AI slop.
Requirements.txt Generator — Build pip requirements.txt Online (Free)
Free online requirements.txt generator: pick Python packages, set version pins, add extras, markers and pip options.
Response JSON Generator
Interactive mock API JSON response generator supporting JSend, JSON:API, RFC 7807, and standard REST HTTP status payloads.
Rich Text Converter
Interactive Rich Text converter between WYSIWYG HTML, Markdown, BBCode, Plain Text, and Slack markdown.
Rotational Kinetic Energy Calculator: 1/2 I omega^2, 8 Inertia Shapes, RPM Solver | nrtechstudio.com
Free rotational kinetic energy calculator: E = 1/2 I omega^2 with an 8-shape moment of inertia library (cylinder, sphere, rod, hoop, point mass), rad/
RSS Feed Generator — Create RSS 2.0 XML
Free RSS feed generator — create valid RSS 2.0 XML online with live preview, validation, and one-click download.
RV Loan Calculator — Payment, Amortization & Affordability
Free RV loan calculator: monthly payment, yearly amortization schedule, affordability (DTI) check, and side-by-side scenario comparison. 100% client-side.
Sales Commission Calculator — Tiered, Accelerator & OTE | nrtechstudio
Free sales commission calculator: graduated & retroactive tiers, accelerators, kickers, quota attainment, splits, clawbacks, draws and OTE. See every step of the math. 100% client-side — your numbers never leave your browser.
Sample YAML File Generator, Formatter & Validator
Free online sample YAML file generator, YAML formatter online, validator, and fixer. Explore YAML examples, Docker/K8s templates, syntax guides, and learn how to write a YAML file.
Tool - See JSON Online Viewer, Formatter & Validator
High-speed online JSON viewer, JSON decoder, tree inspector, UTF-8 validator, and JSON to string code generator.
Shade Sail Size Calculator
Free shade sail size calculator: sail dimensions, attachment layout, post heights, hypar twist, hardware takeoff, shade % and cost for 3- or 4-point sails.
Shaft Size Calculator (Shaft Size) — Power to Diameter, DIN 6885 Keyway, Critical Speed
Free shaft size calculator: motor power (kW/HP) + RPM becomes torque then minimum diameter, DIN 6885 keyway, metric/inch standard shaft sizes, and critical speed. 100% client-side.
Shell Escape — Quote Strings Safely for Bash, CMD & PowerShell
Shell escape tool: safely quote strings for bash, sh, cmd & PowerShell. Single-quote, backslash & double-quote modes, char-by-char view. 100% client-side.
Shell Unescape — Strip Quoting Back to Raw Text
Shell unescape tool: strip bash, sh, cmd & PowerShell quoting back to raw text. Auto-detect mode, 5 unescape modes, argv split view. 100% client-side.
Signal-to-Noise Ratio (SNR) Calculator — Power, Voltage, Friis Cascade, ENOB & Shannon
Free SNR calculator: calculate signal-to-noise ratio from power (W/mW/dBm) or voltage, cascade degradation, ENOB, and Shannon capacity. 100% client-side.
Skateboard Size Calculator — Deck Width, Truck & Wheel Size Finder
Free skateboard size calculator: deck width from shoe size, age and riding style, truck size matcher, wheel size guide and kids sizing chart.
Snowboard Length Calculator — Board Size, Waist Width & Stance Finder
Free snowboard length calculator: board size from weight, skill and riding style, waist width from boot size, stance width and angles, kids sizing, camber vs rocker guide and flex rating.
Sql Converter
SQL String Escape — Online SQL Escape Tool
Free online SQL string escape tool: MySQL backslash mode, PostgreSQL/ANSI and SQL Server quote-doubling, per-character transformation table, worked examples. 100% client-side.
SQL FOR XML PATH Generator
Interactive T-SQL query generator for SQL Server string concatenation and XML data modeling using FOR XML PATH('').
SQL Generator
Interactive visual SQL query and DDL statement generator supporting MySQL, PostgreSQL, SQLite, and SQL Server.
SQL Linter - Free Online SQL Query Checker & Anti-Pattern Detector
Free online SQL linter: paste any query and get instant heuristic checks for SELECT *, missing WHERE on UPDATE/DELETE, implicit JOINs, trailing commas, keyword casing, N+1 patterns and more. 100% client-side.
Sql Query Formatter
SQL Query Sample Library & Builder
Interactive SQL query sample library and template builder covering Joins, CTEs, Window Functions, and Upserts across PostgreSQL, MySQL, SQL Server, and SQLite.
Sql To Json
Convert SQL Insert statements to a JSON array.
SQL to MongoDB Converter
Free SQL to MongoDB converter: SELECT, WHERE, GROUP BY, INSERT, UPDATE, DELETE to Mongo shell, Mongoose and PyMongo. 100% client-side.
SQL Type Cast Generator
Interactive SQL CAST, CONVERT & TRY_CAST query builder across SQL Server, PostgreSQL, MySQL, Oracle, and SQLite.
SQL String Unescape — Online SQL Unescape Tool
Free online SQL string unescape tool: reverse MySQL backslash escapes, PostgreSQL '' doubling and E'' strings, SQL Server quote-doubling. Auto-detect dialect, double-escape warnings, round-trip verification. 100%% client-side.
Staircase Calculator — Riser, Stringer, Code & Cost
Free staircase calculator: solve risers and treads, plan straight/L/U runs, lay out stringers, check IRC code, take off materials and estimate cost. 100% client-side.
Stock Average Calculator
Free stock average calculator: average cost per share across lots, average-down planner, break-even price and unrealized P/L.
String to Base64URL Encoder
Standalone one-way string-to-Base64URL encoder. UTF-8 aware, padding toggle, per-chunk byte mapping, batch mode. 100% client-side.
String Padding Tool
Professional String Padding Tool Online, Left/Right/Center Text Formatter, and Zero-Pad Generator with 100% SEMrush keyword optimization.
SVG Optimizer — Minify SVG Code Online
Free online SVG optimizer: minify SVG code, remove metadata and bloat, round path precision, with live preview and before/after size comparison. 100% client-side.
SVG Placeholder — Generate Custom SVG Placeholder Images
Free online SVG placeholder generator: custom dimensions, solid or gradient background, custom text, border radius and grid/diagonal patterns. Copy SVG code, data URI, HTML or CSS snippet, or download the .svg file. 100% client-side.
SVG to Base64 — Encode SVG as Data URI
Free online SVG to Base64 converter: paste SVG code and get a Base64 or URL-encoded data URI, CSS background-image snippet, live preview and download. 100% client-side.
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How to Use the Tools Directory
Every tool is a single interactive page: enter your inputs, get instant results, no account needed. Use the search box (shortcut: press /) to jump straight to a tool, or browse categories when you are exploring. Each card links to the tool's permanent URL, which you can bookmark or share.
Because all computation happens in your browser, the tools are fast, private, and free forever. If a result looks wrong, use the one-click report control on the tool page so it can be fixed.
Tool Categories at a Glance
| Category | What you will find | Example tasks |
|---|---|---|
| Developer | Encoders, formatters, regex, network tools | Format JSON, test regex, subnet a network |
| Finance | Tax, loans, salary, investing | Estimate tax brackets, amortize a loan |
| Home improvement | Estimators, measurements, materials | Size a wire, estimate paint or flooring |
| Health & fitness | Body metrics, nutrition, workouts | Track BMI, plan calories, score fitness tests |
| Math & science | Converters, geometry, statistics | Convert units, solve triangles |
| Text | Counters, sorters, generators | Count words, alphabetize a list |
| Color | Pickers, converters, checkers | Convert HEX to RGB, check contrast |
| Everyday life | Cooking, travel, automotive, pets | Convert recipes, plan fuel costs |
Popular Tasks and Where to Start
| I want to... | Start with | Why |
|---|---|---|
| Convert between number bases | Binary Converter | Step-by-step base conversion with charts |
| Validate and format data | JSON Formatter | Pretty-print and check JSON instantly |
| Count words for an essay | Word Counter | Words, characters, reading time |
| Check password strength | Password Strength Meter | Entropy-based strength scoring |
| Grade text readability | Readability Score | Flesch-Kincaid and grade levels |
| Audit color contrast | Accessibility Checker | WCAG contrast ratios in one click |
Tools Directory FAQ
What is the NRTechStudio tools directory?
It is a free catalog of more than 2,700 interactive web tools: calculators, converters, generators, and checkers for developers, finance, home improvement, health, education, and everyday tasks.
Are all the tools really free?
Yes. Every tool in the directory is free to use with no sign-up, no trial, and no paywall. They run entirely in your browser.
Do I need to create an account?
No. There are no accounts, logins, or subscriptions. Open a tool and use it immediately.
Is my data private when I use these tools?
Yes. The tools are 100% client-side: your inputs are processed by JavaScript in your own browser and never sent to a server.
How do I find the right tool?
Use the search box at the top of the directory (press / to focus it), or browse by category. Every tool card shows a short description of what it computes.
Do the tools work on mobile?
Yes. The directory and the tools use responsive layouts that adapt to phones, tablets, and desktops.
How many tools are there?
The directory holds more than 2,700 tools and grows regularly as new calculators and converters are published.
Can I request a new tool?
Yes. Each tool page has a report/feedback control you can use to request features or new tools; requests help prioritize what gets built next.
Are the tools accurate?
Calculators use published formulas and reference data (tax tables, NEC ampacity, standard conversions). Each tool page documents its method, and issues can be reported in one click for a fix.
Do tools work offline?
Once a tool page has loaded, most tools keep working without a connection because the logic is client-side JavaScript. The directory search needs the page loaded first.
What categories are covered?
Developer utilities, finance and tax, home improvement, health and fitness, math and science, text tools, color tools, networking, education, and everyday life calculators, among others.
Can I bookmark or share a tool?
Yes. Every tool has its own permanent URL under nrtechstudio.com/tools/, which you can bookmark or share directly.
Is there an API for these tools?
The tools are interactive web pages, not API endpoints. The underlying math is plain JavaScript you can inspect in the page source.
Why do some tools show ratings?
Ratings aggregate user feedback to surface the most trusted tools and flag pages that need fixes or better explanations.
How often are new tools added?
New tools are published on a continuous pipeline, prioritized by measured search demand and by user requests from the feedback controls.
Who builds these tools?
NRTechStudio, an independent tools studio focused on free, private, client-side utilities that respect user privacy.