Free Online Tools for Everything You Do
Browse 2,706+ free interactive tools - home improvement estimators, pet calculators, cooking converters, automotive tools, finance planners, fitness calculators, developer utilities and more. No sign-up. 100% private. Runs entirely in your browser.
Inverse Square Law Calculator
Free inverse square law calculator: solve I1/I2 = (d2/d1)^2 for intensity or distance. Presets for light (lux), sound (dB SPL, 20*log10), gravity, and radiation, plus a doubling-distance table. 100% c
Inverting Buck-Boost Converter Calculator — Duty Cycle, Inductor & Output Ripple | nrtechstudio.com
Free inverting buck-boost converter calculator: duty cycle, inductor ripple current, output ripple voltage, CCM/DCM boundary (L_min), peak-current inductor rating and L/C component selection for negative-rail DC-DC designs.
Investment Fees Comparison Calculator — See What Fees Really Cost
Compare investment fee scenarios side by side: initial investment + annual contributions, gross return, and up to 3 fee levels. See future value with vs without fees, fee drag in dollars and percent, and break-even alpha.
Investment Inflation Calculator — Real Return After Inflation | nrtechstudio.com
Investment inflation calculator: find your real return after inflation and project nominal vs inflation-adjusted growth. Free, instant, no signup.
Invisible Text Generator — Zero-Width Characters, Hidden Messages & Detector
Free invisible text generator. Copy zero-width characters (U+200B, U+200C, U+200D), hide secret messages, inspect codepoints. 100% client-side.
IP to Decimal — Convert IPv4 Address to Decimal
Convert any IPv4 address to its decimal integer with the full step-by-step calculation shown. Free online IP to decimal converter with batch mode, binary/hex views, validation and worked examples. 100% client-side.
IP to Hex Converter — IPv4 to Hexadecimal
Convert IPv4 to hex free: dotted hex (C0.A8.01.01), 0xC0A80101, 32-bit decimal and binary, per-octet math steps, plus batch mode.
IP to Octal Converter
Free IP to octal converter — convert an IPv4 address to octal (dotted + 32-bit) with per-octet steps, batch mode, and validation.
Ipv4 To Binary
Convert an IP address to its binary representation.
IPv4 to IPv6 Converter — Mapped, 6to4, Teredo, ISATAP & NAT64
Convert IPv4 to IPv6 free: mapped, 6to4, Teredo, ISATAP & NAT64 addresses in full, compressed and mixed notation, plus reverse IPv6-to-IPv4 and batch mode.
IPv6 Compressor — RFC 5952 Shortest Form, Steps & Batch
Compress an expanded IPv6 address to the shortest RFC 5952 canonical form free: per-segment compression steps, longest-zero-run detection, tie-breaking, address validation, batch mode, copy and CSV/TXT download.
IPv6 Expander — RFC 4291 Full Form, Steps & Batch
Expand a compressed IPv6 address to the full 8-group RFC 4291 form free: per-segment expansion steps, strict address validation, batch mode, copy and CSV/TXT download.
IPv6 Subnet Calculator — CIDR Ranges, Splitter & Reverse DNS
Free IPv6 subnet calculator: network address, full range, /64 & /48 counts, subnet splitter, binary view and reverse DNS for any prefix. 100% client-side.
IQ Percentile Calculator — IQ to Percentile, Percentile to IQ, Classification Table
Free IQ percentile calculator: convert IQ score to percentile (Wechsler SD 15, Stanford-Binet SD 16, Cattell SD 24), percentile back to IQ, z-score, r
IRA Calculator — Traditional vs Roth IRA Growth Projector (2026 Limits)
Free IRA calculator: project Traditional vs Roth IRA growth side by side with 2026 IRS contribution limits ($7,500 / $8,600 catch-up), RMD age 73 flag, and early-withdrawal penalty notes. 100% private, runs in your browser.
Is It a Right Triangle? — Right Triangle Checker Calculator
Enter any 3 side lengths to check whether they form a right triangle. Verifies a²+b²=c² with float tolerance, classifies acute / right / obtuse, and computes angles, area (Heron) and perimeter with a live diagram.
Isentropic Flow Calculator — Mach Number, Pressure, Temperature & Area Ratios | nrtechstudio.com
Free isentropic flow calculator: enter Mach number to get T0/T, p0/p, density ratio, A/A* area ratio, Mach angle and Prandtl-Meyer angle — or solve the inverse (Mach from A/A*, T0/T, p0/p) with subsonic/supersonic branches. Interactive isentropic flow table, choked-flow guide. 100% in-browser, no sign-up.
Isosceles Triangle Calculator — Side, Angle, Area & Perimeter Solver | nrtechstudio.com
Free isosceles triangle calculator and solver. Enter two equal sides + base, side + apex angle, base + base angle, or height + base to get all sides, both angles, height, area, and perimeter — with a live diagram and worked examples.
IVF Cost Lab — IVF Total Cost Estimator (7-in-1 Suite)
Free IVF total cost estimator: per-cycle cost ranges, state insurance-mandate checker (23 jurisdictions), add-on menu (ICSI, PGT, freezing), multi-cycle planner, financing comparator, clinic quote comparison, and medication estimator. 100% client-side, no signup.
IVF Due Date Calculator — EDD by Transfer, Retrieval & FET Date
Free IVF due date calculator: estimate your due date from embryo transfer date (day 3 / day 5 / day 6), egg retrieval date, or frozen embryo transfer (FET) date. Get gestational age, trimester, milestones and equivalent LMP. 100% client-side, no signup.
IVIG Dose Calculator — Total Dose, Infusion Volume & Titration Schedule
Free IVIG dose calculator: estimate total immunoglobulin dose (g), daily dose, infusion volume for 5% or 10% products, and a titrated infusion schedule by weight (kg/lb). Educational estimate only — not medical advice.
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.
Java Escape — Escape & Unescape Java Strings Online
Free online Java string escape tool. Escape quotes, backslashes, newlines, tabs and Unicode into valid Java string literals (JLS §3.10.6), or unescape Java literals back to text. 100% client-side.
Java to JSON Converter
Convert Java Class and POJO model definitions into valid mock JSON objects instantly with Jackson, Gson, and Lombok support.
JavaScript Beautify – JS, YAML & Markdown Formatter
Yaml formatter, javascript beautify, yaml 格式化, formatter js, javascript style, markdown generator, markdown examples, url formatter, notepad json formatter, markdown link image, pretty format json, markdown text editor, yaml file formatter, markdown indent image, markdown javascript, online formatter js, js 格式 化, online formatter javascript, markdown file type, what is markdown editor, javascript prettify online, javascript beauty, markdown website, markdown show image, javascript markdown renderer, markdown rendered, yaml creator, markdown inline images, js 格式化, online yaml viewer.
JavaScript Code Editor, Web Sandbox & Next.js vs React Guide
Free in-browser JavaScript code editor and web playground. Run JavaScript scripts, test HTML/CSS/JS, execute console outputs, inspect Next.js vs React architectures, and access modern boilerplates.
JavaScript JSON Serializer & Parser
Interactive JavaScript JSON.parse vs JSON.stringify testing playground, safe deserializer, and Node.js code generator.
JavaScript Map to JSON Serializer
Interactive converter and code generator for serializing ES6 Maps, Sets, and BigInt to JSON and back.
JavaScript Next & Next.js Online Editor
Free online JS code editor, JavaScript Next playground, and Next.js releases tracker. Test ES2024 features and inspect Next.js logo assets.
JavaScript Pretty Print JSON & Beautifier
Interactive JSON validator, JavaScript JSON formatter, Java POJO generator, and HTML code beautifier tool.
JavaScript Replace Replace – String Replace & Split Tool
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Jensen's Alpha Calculator — Portfolio α vs CAPM
Calculate portfolio Jensen's alpha: α = Rp − [Rf + β(Rm − Rf)], CAPM expected return, 4-way reverse solver, and two-manager comparator. With substitution steps and descriptive interpretation.
Jet Lag Calculator — Recovery Days & Day-by-Day Adaptation Plan
Free jet lag calculator: enter two cities and your flight to get the time difference, jet lag severity, recovery days estimate, a day-by-day adaptation plan (light, sleep, melatonin timing) and an in-flight sleep optimizer. 100% client-side, no signup.
Job Offer Comparison Calculator — Total Compensation Compared | nrtechstudio.com
Free job offer comparison calculator: compare up to 3 job offers side by side on total compensation — base salary, bonus, RSU equity vesting, 401(k) match, PTO value, health premiums, taxes, and remote vs onsite costs. 100% client-side, no signup.
Job Posting Schema Generator
Interactive Google for Jobs compliant Schema.org JobPosting structured data generator with remote work and salary support.
Joule Heating Calculator - P = I2R Power, Energy and Temperature Rise
Free Joule heating calculator: solve P = I2R = V2/R = VI for power, current, voltage or resistance, compute heating energy over time, and estimate temperature rise. 100% client-side.
Joule to Kcal & Energy Units Converter
Free online Joule to Kcal calculator and energy conversion tool. Convert joules to calories, cal to joules, kJ to kcal, and explore step-by-step energy conversion formulas.
Joules to Kilojoules Converter (J to kJ)
Free joules to kilojoules converter. Convert J to kJ and kJ to J instantly, plus the full energy unit ladder (MJ, cal, kcal, Wh, eV), formulas, quick tables and FAQs.
Free JPG to PDF Converter — Combine Multiple JPGs Into One PDF
Free JPG to PDF converter: combine multiple JPG/JPEG images into one PDF, 100% in your browser. Reorder pages, A4/Letter/fit-to-image, margins, quality control. No upload, no watermark, no signup.
JPG to PNG Converter — Free, No Upload, 100% In-Browser
Convert JPG to PNG free right in your browser. Multi-file batch, resize, before/after preview with honest size comparison. No server upload, no watermark.
JQ Format JSON & Query Playground
Interactive online JQ query evaluator, JSON formatter, and filter expression tester.
JS Char Code Generator
High-performance bidirectional JavaScript CharCode converter, charCodeAt and String.fromCharCode online tool with UTF-16/UTF-32 and ASCII table analysis.
JavaScript JSONPath Evaluator
Interactive JSONPath query evaluator, expression tester, and JavaScript code generator.
JS Linter — Check JavaScript Code Online
Free online JavaScript linter. Heuristic client-side JS code checker: var vs let/const, == vs ===, missing semicolons, console.log leftovers, debugger, eval, unbalanced braces. No uploads.
JS Minifier — Minify JavaScript Online Free
Free online JS minifier — minify JavaScript code, compress JS, strip comments and whitespace, reduce file size. Includes JS beautifier, syntax validator and console.log detector. 100% client-side.
JS Object to CSS Converter - React Inline Styles to CSS
Convert JS style objects to CSS: React inline styles or Emotion/JSS objects become kebab-case CSS with automatic px units, &:hover and @media support.
JavaScript Formatter & Beautifier Online
Free online JavaScript formatter and JS code beautifier. Format JS code, javascript formatting online, JS code formatter, javascript code formatter, javascript beautification, javascript code beautifier, javascript formatting, js code beautify, format js code online.
JavaScript & JSON Unescape Tool & String Decoder
Standalone professional JavaScript unescape tool, JSON unescape utility, and JS string decoder. Escape characters JS, javascript escape string, and unescape JS strings online with zero AI slop.
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Try a different keyword like "calculator", "planner", "converter" - or pick a category above.
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.