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.
EVA Foam Thickness & Density Picker for Cosplay Armor | eva-foam-lab
Pick the right EVA foam thickness (2-10mm) and density (38-80 kg/m3) for every cosplay armor piece: helmet, chestplate, bracers, sword, shield. Free sheet estimator, Worbla vs EVA helper, heat-shaping guide.
EXIF Viewer — View Remove Photo Metadata Online (Free, Private)
Free online EXIF viewer: see all camera, exposure & GPS metadata in any photo, check your privacy risk score, and remove EXIF data before sharing. 100% client-side — photos never leave your browser.
Extract Email Address From Contact Record – Email Extractor & Finder
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Face Shape Calculator — Find Your Face Shape Free
Free face shape calculator: enter forehead, cheekbone, jawline and face length measurements to find your face shape (oval, round, square, heart, diamo
FAQ Schema Markup Generator
Interactive FAQPage Schema.org JSON-LD generator with live Google SERP preview and validation.
Favicon Generator — Free Multi-Size ICO + PNG Maker (No Upload)
Free favicon generator that runs 100% in your browser: make a favicon from an image, text, emoji or initials. Exports 16x16, 32x32, 48x48, apple-touch-icon, 192 & 512px PNGs plus a real multi-size favicon.ico, HTML snippet and web manifest. No upload, no signup.
Find and Replace Online Text Tool
Free online find and replace tool with regex support. Text replacer, search and replace string utility, regex find and replace, and mass find and replace text with instant live preview.
Floor Lamp Size Calculator — Height, Arc, Torchiere & Shade Sizer | nrtechstudio.com
How tall should a floor lamp be? Free floor lamp size calculator: ceiling-fit height, arc lamp reach, torchiere & reading lamp sizer, shade proportion
Font Pairing Generator — Google Font Combinations
Free font pairing generator: curated Google Font combinations by style, live heading and body previews, and copy-paste embed code plus CSS.
FormData to JSON Converter
Convert URL-encoded form data, multipart/form-data, query strings, and HTML forms into structured JSON objects.
Fountain Pen Nib Size Converter: Brand-to-Brand Chart, mm Widths & Line Renderer
Free interactive fountain pen nib size converter: convert nib grades brand-to-brand (Japanese F ≈ Western EF), browse curated mm line-width charts for 12 brands, render true-scale line widths, and decode every nib grade. No sign-up, 100% client-side.
Fraction to Percent Converter (with Steps) — nrtechstudio
Free fraction to percent calculator with show-your-work steps. Convert fractions to percents and percents to simplified fractions, including mixed numbers. Repeating decimals flagged honestly. 100% client-side — your data never leaves your browser.
Frequency Converter — Hz, kHz, MHz, GHz, RPM, rad/s & Wave Calculator | nrtechstudio
Free frequency converter: Hz, kHz, MHz, GHz, THz, mHz, rpm, rad/s, deg/s two-way conversion, plus period, wavelength (vacuum/air/water/fiber/sound), angular frequency, motor sync speed, Nyquist & aliasing, and a radio-band finder. 100% client-side — data never leaves your browser.
Git Ignore Generator & Fixer Tool
Interactive .gitignore generator and troubleshooting assistant for git ignore not working, cache clearing, and rule syntax.
.gitignore Generator & File Template
Free online gitignore generator to create .gitignore files for Node.js, Python, Java, React, Laravel, .NET, Android, and Rust. Includes gitignore syntax reference, how to use gitignore, gitignore for directory and folder examples.
go.mod Generator
Free online go.mod generator: build a valid Go module file with module path, Go version, require (direct/indirect), replace, exclude, retract and toolchain directives — 100% client-side.
Gradient Color Combination & CSS Gradient Studio
Interactive gradient color combination generator, linear & radial gradient maker, 3-color mixer, CSS text gradient, and photo palette extractor.
CSS Gradient Generator & Maker
Professional multi-color CSS gradient maker, linear and radial gradient builder, dark gradient CSS generator, text font gradient, and mesh gradient tool online.
Graham Number Calculator — Value Investing Stock Valuation
Graham Number calculator: fair value from EPS and BVPS via √(22.5 × EPS × BVPS). Compare vs market price, reverse-solve a variable, compare two stocks.
CSS Grid Calculator — Column Widths & Layout Generator
Calculate CSS grid column widths in seconds — fixed & fluid 12-column layouts, gutter math, breakpoint presets & copy-ready CSS/Tailwind code. 100% client-side.
Guest Room Size Calculator — 7 Layout Modes for the Perfect Guest Bedroom
Free guest room size calculator: 7 layout modes for bed fit, walkway clearance, dresser, luggage zone, ensuite vs shared bath, closet and room planner
Hex to Base64URL Converter — Hexadecimal to URL-Safe Base64
Convert hex to base64url free: 0x prefix and spaced hex accepted, byte grouping shown, padding option, batch mode. 100% client-side.
Hex to IP Converter — Hexadecimal to IPv4 Address
Convert hex to IP free: 0xC0A80101, C0A80101, or dotted hex (C0.A8.01.01) to IPv4. Per-byte math steps, class/scope detection, batch mode.
HMAC Generator & Verifier — HMAC-SHA256 Online (Free, No Signup)
Free online HMAC generator & verifier: compute HMAC-SHA256, HMAC-SHA512, HMAC-SHA1, and HMAC-MD5 in your browser. Verify API signatures & webhooks. 100% client-side — your secret key never leaves your device.
Hockey Stick Length Calculator — Size, Flex, Lie & Cut-Down Guide
Free hockey stick length calculator: size by height, flex by weight, lie guidance, cut-down flex change.
Holding Period Return (HPR) Calculator — Formula, Annualized & Comparator
Calculate holding period return (HPR) from initial value, final value, and dividends/income. Includes annualized HPR, reverse solver, and a 2-investment comparator — free, 100% in your browser.
Horse Blanket Size & Type Lab — Measure, Size, Turnout vs Stable, Fill Guide | nrtechstudio.com
Free horse blanket size calculator: measure chest-to-tail to find blanket size, between-size rule, turnout vs stable vs sheet advisor by temperature, denier & fill (grams) guide, fit checker, inch/cm/EU conversion and layering planner.
HTML Anchor & OnClick Link Generator
Interactive HTML anchor generator, href builder, and onclick JavaScript event tester. Test live link behavior and copy clean code.
Htaccess Redirect Generator — 301/302/307 Redirects, RedirectMatch & RewriteRule
Free online htaccess redirect generator: 301/302/307/308 rules, RedirectMatch regex builder, www to non-www, HTTP to HTTPS and trailing-slash canonicalization, bulk rules, redirect loop validation. 100% client-side.
HTML Entity Encoder & Decoder - Escape/Unescape HTML Online
Free HTML entity encoder & decoder: convert special characters to named, decimal or hex HTML entities, decode entities back, with live mode and a click-to-insert entity reference table. 100% client-side.
HTML Entity Decoder — Decode HTML Entities to Text Online
Free one-way HTML entity decoder: turn named, decimal & hex HTML entities into characters in your browser. Per-entity mapping, honest invalid-entity errors, searchable 2,231-entity reference.
HTML Link Generator & Hyperlink Maker
Standalone professional HTML link generator, hyperlink maker, and URL link generator. Create a href tags easily, generate HTML anchor tags online, and build SEO-safe website links with zero AI slop.
Free Online HTML Linter — Check HTML Errors, Accessibility & Best Practices
Free online HTML linter: find missing alt text, duplicate IDs, deprecated tags, heading skips and 29 rules line by line. Private, in-browser, no signup.
HTML List Generator — Convert Text to UL, OL & DL
Free HTML list generator: convert text to <ul>, <ol> or <dl> markup with nested lists, custom bullets, numbering styles, start/reversed attributes, live preview, copy & download. 100% client-side.
Html Minifier
Minify HTML code to reduce file size.
Html Table Div
Convert <table> tags to CSS Grid <div> layouts.
HTML Table Generator — Free Online HTML Table Code Builder
Free HTML table generator: build tables in a spreadsheet-like grid, style them, and copy clean HTML, Bootstrap, Tailwind, or Markdown code. 100% client-side.
HTML to BBCode Converter
Free online HTML to BBCode converter — paste HTML markup and get forum-ready BBCode for phpBB, vBulletin, XenForo, SMF and MyBB with live preview. 100% client-side.
HTML to Markdown Converter
Free bidirectional HTML to Markdown converter. Convert HTML to Markdown online and Markdown to HTML with live preview, tables, code fences, copy and download. 100% client-side.
HTTP Headers Generator (Standalone)
Generate HTTP response headers online: HSTS, CSP, X-Frame-Options, Referrer-Policy, Permissions-Policy, caching and CORS with paste-ready output for Apache, Nginx and Express. 100% client-side.
HTTP Headers Parser (Standalone)
Parse raw HTTP headers into JSON, an explained table, validation and security analysis. 100% client-side.
HTTP Status Lookup — Every HTTP Status Code, Meaning & Fix
Free HTTP status code lookup: search 55+ HTTP status codes (200, 301, 404, 500…) by code or phrase, filter by category, see when each code happens, example scenarios and how to fix error codes. 100% client-side.
Hz to Radians Converter — Hz ↔ rad/s, RPM, deg/s Calculator | nrtechstudio
Free Hz to rad/s converter: convert hertz to radians per second (ω = 2πf) and back, plus RPM, rev/s, degrees/second, period, motor shaft speed, tip speed, and waveform angular frequency. 100% client-side.
IBAN Validator — Free IBAN Checker, Calculator & Generator (89 Countries)
Free IBAN validator suite: check any IBAN (MOD-97 + per-country format), parse BBAN structure for 89 countries, generate test IBANs, calculate IBAN from domestic account numbers, bulk-validate lists. 100% client-side — nothing leaves your browser.
Email Password Leak Checker & Security Lookup
Free online email password leak checker and breach lookup. Learn how to check the password leak online, identify email address vulnerabilities, verify compromised passwords, and run URL legit check safely.
Image To Json
Image to Markdown Converter
Standalone professional image-to-markdown generator. Convert an image URL to Markdown image syntax with alt text, title, linked-image, reference-style, batch gallery and HTML img fallback.
Standalone - Jacket Size Calculator
Jacket size calculator: turn chest or bust measurements into US, UK & EU jacket sizes, sleeve length, length code (S/R/L) and fit guidance.
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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.