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.
JSON Unstringify & Stringify Online Tool
Interactive JSON unstringify online tool, JSON unescape parser, beautifier, and multi-language object serializer for Java, Python, and JavaScript.
JSON Value Extractor — Extract All Primitive Values
Extract every primitive value from JSON online free: strings, numbers, booleans, nulls. Type filters, JSONPath locations, unique, sort, CSV/JSON export. 100% client-side.
Article Schema Generator
High-performance Article Schema Generator and structured data markup generator for Schema.org JSON-LD Article, BlogPosting, NewsArticle, and Google News schema.
Jsonpath Tester
Mock JWT Generator
Interactive Mock JWT Generator, Test JWT Token Creator, and Dummy JWT Signer with 100% SEMrush keyword optimization.
JWT Token Node.js – jsonwebtoken Implementation & Inspector
JWT token node js, json web token, json web token example, jwt token structure, jwt js, jwt javascript, json web token java, inspect json web token online, view jwt payload and header.
Kubernetes YAML Validator & Lint Tool
Free online Kubernetes YAML validator and YAML lint tool to check Kubernetes manifests for syntax errors, schema conformance, and security best practices.
Levothyroxine Dosage Calculator — Starting Dose by Weight, Tablet Combos & Missed Dose Guide | nrtechstudio.com
Levothyroxine dosage reference: starting dose estimator by weight (label ~1.6 mcg/kg/day), elderly/cardiac and pregnancy adjustments, commercial table
Ligation Calculator — Vector:Insert ng for DNA Cloning | nrtechstudio.com
Free ligation calculator for molecular biology: convert vector ng and kb sizes into exact ng of insert for any molar ratio (1:1, 3:1, 5:1, custom). Double-digest two-insert mode, vector-only control planner, reaction scale-up, ng to pmol/fmol converter. 100% client-side and private.
Line Number Adder
Professional Text Line Numbering Tool, Code Gutter Formatter, and Line Counter with 100% SEMrush keyword optimization.
Link Verification & URL Safety Checker
Free online link verification and hyperlink checker tool. Verify URL safety, validate links, check valid website addresses, and inspect site validity instantly.
LRINEC Score Calculator — Necrotizing Fasciitis Risk (Wong 2004)
Free LRINEC score calculator (Laboratory Risk Indicator for Necrotizing Fasciitis, Wong et al. 2004): 6 lab criteria, risk bands, and lab unit convers
MAC Address Formatter & Editor
Professional MAC address editor, normalizer, and batch formatter tool supporting Cisco, Windows, Linux, and EUI-48 formats.
Markdown Table Generator — CSV/Excel to Markdown Tables (Free, Discord Mode)
Free markdown table generator: paste CSV, Excel or Google Sheets data and get clean GitHub-flavored markdown tables with alignment control, pipe escaping, line breaks, merge cells (HTML mode) and a Discord table mode. 100% private, in your browser.
Maximum Drawdown Calculator — Peak-to-Trough, Duration & Recovery
Compute maximum drawdown (MDD) from a portfolio value series or per-period returns. Includes drawdown duration, a 2-strategy comparator, and a recovery-gain solver. Free, 100% in-browser.
Markdown AST Parser - Free Online Markdown Syntax Tree Explorer
Free Markdown AST parser — turn Markdown into an abstract syntax tree online. Collapsible tree view, exact line:col node positions, raw JSON with highlighting, GFM tables & task lists. 100% client-side.
Markdown Linter Online — Check Markdown Style Rules
Free online Markdown linter. Heuristic client-side checks for 15 markdownlint-style rules (MD001-MD047): headings, trailing spaces, blank lines, lists, code fences, line length. No uploads, no signup.
Markdown to BBCode Converter
Free Markdown to BBCode converter — convert Markdown to BBCode online with live preview. Headings, bold, italic, links, images, lists, tables, code and quotes for phpBB, vBulletin, MyBB and SMF forums. 100% client-side.
Markdown to JSX Converter - Free Online React Component Generator
Free Markdown to JSX converter — turn Markdown into React components online with live editor, syntax map, copy & download .jsx. 100% client-side.
Melatonin Dosage Guide Calculator — How Much Melatonin Should I Take?
Melatonin dosage guide calculator: adult dose ranges (start low 0.5–1 mg, typically up to 5 mg), timing tips (30–60 min before bed), jet lag schedule,
MIME Type Lookup
Free MIME type lookup: enter a file extension to get its MIME type, or reverse-search a MIME type to find matching extensions. 354 types, one-click copy, 100% client-side.
Modular Scale Calculator — Typography Scale Generator
Free modular scale calculator: build harmonious typography scales from any base size and ratio, with live preview and CSS variable export. 100% client-side.
Net Operating Working Capital (NOWC) Calculator — Net Operating Working Capital
Compute net operating working capital (NOWC) from balance-sheet components or from total current assets and current liabilities. With a two-company comparator and a NOWC target solver.
Nginx Config Linter & Syntax Checker Online
Free online nginx config linter. Validate nginx.conf syntax, catch typos, bad nesting, and risky patterns in your browser.
Nginx Redirect Generator — Free 301/302 Redirect Builder
Free nginx redirect generator. Build copy-paste 301/302 rules: return 301, rewrite permanent, https, www, domain moves, with per-line explanations and loop checks.
NPSH Calculator — Net Positive Suction Head, Margin & Cavitation Check | nrtechstudio
Free NPSH calculator: compute NPSHa from atmospheric pressure, vapor pressure, static suction head and friction loss; check NPSH margin vs NPSHr with
Number Base Converter - Binary, Octal, Decimal, Hex, Base 2-36
Free number base converter with live-synced binary/octal/decimal/hex boxes, any base 2-36,
Online Sql Compiler
Operating Asset Turnover (OAT) Calculator — Operating Asset Turnover
Calculate operating asset turnover (OAT): net sales divided by average operating assets. With turnover days, component mode from total assets, two-company comparator, and target solver. Free and fully runs in the browser.
Java org.json Code Generator
Interactive Java org.json snippet generator for JSONObject, JSONArray, XML conversion, and Maven dependency configuration.
Outdoor Wood Furnace Size Calculator — BTU, Firebox, Burn Time & EPA Guide
Outdoor wood furnace size calculator: BTU sizing by climate zone, firebox, burn time, water capacity, wood vs propane/oil cost, and EPA setback guidan
Parallel Capacitor Calculator — Series, Parallel & Combination + Code Finder
Free capacitor calculator: parallel (Ceq = ΣC), series (1/Ceq = Σ1/C) with per-capacitor voltage division, series-parallel combination solver with exp
Parse JSON in SQL Generator
Interactive SQL query generator for querying and extracting JSON columns in MySQL, PostgreSQL, SQLite, and SQL Server.
Patio Umbrella Size Calculator — Table, Base Weight & Cost Planner
Free patio umbrella size calculator: match canopy to your table and seating area, size the base weight, compare mounts and shapes, estimate cost.
PCB Impedance Calculator — Microstrip & Stripline Z0 + Reverse Width Solver
Free PCB impedance calculator: single-ended microstrip Z0, symmetric stripline Z0, and a reverse solver that finds the trace width for a target impedance (50 Ω, 75 Ω...). 100% client-side, with show-your-work formulas and worked examples.
PCB Trace Current Calculator (IPC-2221) — Max Current & Required Width
Free IPC-2221 PCB trace current calculator. Find max current for a trace width (external or internal layer, any copper weight), or the required trace width for your target current. Includes IPC-2221 formula, worked examples, current-capacity chart and FAQ.
PCB Trace Resistance Calculator — R=ρL/A, Copper Weight (oz), Voltage Drop | nrtechstudio
Free PCB trace resistance calculator: R = ρL/A from trace width, length and copper weight (0.5–4 oz). Temperature correction, voltage drop at given current, sheet resistance, and reverse width/length solver. 100% client-side.
Pediatric GFR Calculator (Schwartz Formula) | nrtechstudio.com
Free pediatric eGFR calculator using the 2009 bedside Schwartz formula (eGFR = 0.413 x height / serum creatinine) for children, plus the original Schw
Pergola Size Calculator — Posts, Beams, Rafters, Shade %, Materials & Cost
Pergola size calculator: size by function and guests, post/beam spacing, rafter shade %, material takeoff, cost for lumber/cedar/aluminum + standard s
Phone Number Formatter Online
Free online phone number formatter, telephone number formatting tool, and proper phone number format generator. Format mobile phone number format, E.164, and JS code.
PHP Linter Online — Check PHP Syntax & Code Issues
Free online PHP linter. Heuristic client-side checks for missing semicolons, unbalanced brackets, short open tags, deprecated mysql_* calls, eval() risks and style issues. No uploads, no signup.
Pi Attenuator Calculator — Pi & T RF Attenuator Resistor Values
Design Pi and T resistive attenuators: enter attenuation in dB and impedance in ohms to get exact resistor values, nearest E12/E24 standard values, and actual built attenuation.
Podcast RSS Generator — Apple Podcasts Feed XML
Generate Apple Podcasts RSS feed XML with iTunes tags.
pom.xml Generator
High-performance interactive Apache Maven POM.xml Generator, project file builder, and Maven archetype CLI synthesizer with 100% SEMrush keyword optimization.
Prandtl Number Calculator — Pr = μ·c_p/k Solver, Fluid Table & Boundary-Layer Guide
Free Prandtl number calculator: Pr = μ·c_p/k in 4 solve directions (SI + imperial units), 11-fluid Prandtl table with temperature interpolation, and c
Product Schema Markup Generator
Interactive Product & Offer Schema.org JSON-LD structured data builder for Google Shopping and e-commerce rich results.
PCB Propagation Delay Calculator — Trace Length to Time, Skew Matcher
Free PCB signal propagation delay calculator: convert trace length to flight time (ps/ns), delay budget to max length, match skew for DDR-style buses, and estimate via delay. Stripline and microstrip (Hammerstad-Jensen), 100% client-side.
PowerShell to Bash Converter — Heuristic Line-by-Line Mapping
Convert PowerShell to bash free: line-by-line mapping (Write-Host, Get-ChildItem, Select-String, if, foreach) with honest unmapped flags. 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.