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.
Organization Schema Markup Generator
Interactive Schema.org Organization, Logo, and Brand JSON-LD generator with Google Knowledge Panel preview and sameAs social linking.
Orifice Flow Calculator — Orifice Plate Flow Rate, Cd & Orifice Size Solver
Free orifice flow calculator: flow rate through an orifice plate from Q = Cd·A·√(2·ΔP/ρ), plus reverse solvers for orifice size, pressure drop and discharge coefficient Cd, Cd vs beta-ratio table, gas density tool and Torricelli free-jet mode. Results in m³/s, L/s, GPM, CFM. 100% in-browser.
Ounces to Cups Converter: Fluid Ounces and Dry Ounces to Cups
Convert ounces to cups both ways. Fluid ounces to US, metric and imperial cups (8 fl oz = 1 US cup exactly), plus dry ounces to cups with ingredient densities (flour, sugar, butter, honey, oil, cocoa). Exact definitions, tables, worked examples.
Ounces to Grams Converter: oz to g Calculator
Convert ounces to grams and grams to ounces with the exact international definition (1 oz = 28.349523125 g). Includes troy ounces for precious metals, kg and lb equivalents, a conversion table, and worked examples.
Ounces to Pounds Converter: oz to lb
Convert ounces to pounds and pounds to ounces instantly. 16 oz = 1 lb exact, with gram and kilogram equivalents, precision 0-10 decimals, quick table and worked examples.
Outdoor Kitchen Size Calculator — Grill Zone, Counter, Seating & Pergola
Plan your outdoor kitchen size: grill zone, counter run, sink, fridge, bar seating, pizza oven, clearances and pergola dimensions — free calculator.
Outdoor Storage Box Size Calculator — 7 Ways to Size, Fit & Build a Deck Box
Free outdoor storage box size calculator with 7 modes: size a deck box in gallons from your items, check whether an item fits the interior, plan weatherproofing, compute bench seating capacity, generate a lumber/materials takeoff, check placement wind load and deck weight, and estimate buy-vs-build cost. Runs 100% in the browser.
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
Oven to Air Fryer Conversion Calculator: Temperature and Time Converter - nrtechstudio.com
Free oven to air fryer conversion calculator. Convert any conventional oven recipe to air fryer settings with the standard rule: 25°F less and 20% less time. Includes reverse mode, food presets, reference table, and worked examples.
Overtime Tax Calculator – Hourly Wage, Salary & Tip Pay
Overtime tax calculator, earnings calculator hourly, hourly to yearly pay calculator, job income calculator, daily salary calculator, hourly vs salary calculator, tip tax calculator, day rate calculator salary, hourly to salary conversion calculator, payroll tax calculator hourly, gross pay calculator hourly, online hourly rate calculator, pay calculator day rate.
Ovulation Calculator — Fertile Window & Ovulation Day Estimator
Free ovulation calculator: enter your last period date and cycle length to estimate ovulation day, your 6-day fertile window, and your next 3 periods. Transparent calendar-method formula, 3-month calendar, no signup.
Oxygenation Index Calculator — OI Formula & ECMO Thresholds | nrtechstudio
Free oxygenation index (OI) calculator: OI = (FiO2 x MAP x 100) / PaO2 with FiO2 fraction/percent toggle, PaO2 mmHg/kPa, OSI alternative, target-OI in
P-Score Calculator & Probability Distribution Table
Interactive p-score calculator, p-value from z-score, area of shaded region calculator, and normal distribution table.
Pack Years Calculator — Smoking History in Pack-Years
Free pack years calculator: convert cigarettes per day and years smoked into pack-years, with multiple smoking periods, lifetime cigarette totals, exposure bands, and educational lung-cancer screening context. 100% client-side, no signup.
Package.json Generator
Interactive tool to create package json, make package json, and generating package json configuration files for Node.js, npm, yarn, pnpm, and Bun projects.
Packing List Generator — Smart Travel Packing Checklist | nrtechstudio.com
Free packing list generator: build a custom travel packing checklist by trip type, days, season and destination. Item-per-day quantities, baggage weight estimate, printable checklist. 100% private, no signup.
Padua Score Calculator — VTE Risk in Hospitalized Medical Patients | nrtechstudio
Free Padua Prediction Score calculator: 11 weighted risk factors for venous thromboembolism in hospitalized medical patients, live score 0-20, low/hig
Paint Calculator — How Much Paint Do I Need? (Multi-Room, Primer Cost)
Free paint calculator: how much paint you need for any room, ceiling, trim, doors, cabinets or fence. Multi-room project mode, primer logic, metric/imperial, can optimizer and cost estimator. 100% private, runs in your browser.
House Painting Cost Calculator — Interior, Exterior, Cabinets, Deck | Painting Cost Lab
Estimate your house painting project cost room-by-room: interior, exterior, kitchen cabinets, deck and fence. Prep-level, regional labor and DIY-vs-pro comparison. Free, private, no signup.
Palindrome Checker — Test Words & Phrases Online
Free online palindrome checker: test words and phrases with options to ignore case, spaces, and punctuation, plus a longest palindromic substring finder. 100% client-side.
Pantry Size Calculator — Walk-In & Reach-In Planner (7 Modes)
Free pantry size calculator with 7 modes: walk-in and reach-in sizers, shelf spacing, storage capacity, door clearance, household planner and converte
Paracetamol Dosage Calculator (Acetaminophen 500 mg & 325 mg)
Educational paracetamol (acetaminophen / Tylenol) dose estimator: adult Extra Strength 500 mg caplet and Regular Strength 325 mg tablet schedules, 24-
Paraglider Size Lab — Wing Size Calculator, Reserve Sizer & Wing Loading (EN)
Free interactive paraglider sizing lab: find your wing size from all-up weight using real manufacturer weight ranges (Ozone, Gin, Advance, Nova, Skywalk, BGD, Niviuk, Dudek), border-case advisor, wing loading calculator, paramotor mode, speed/mini-wing sizer, reserve parachute sizer and tandem weight-limit checker.
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
Parallel Inductors Calculator — Leq, Mutual M, Energy & Reactance | nrtechstudio
Free parallel inductor calculator: equivalent inductance 1/Leq = sum(1/Li) for up to 8 inductors, series with mutual inductance M = k*sqrt(L1*L2) and
Parallel Resistor Calculator — Rt, Current Division, Power & E12/E24 Picker
Free parallel resistor calculator: equivalent resistance for 2–8 resistors, current division per branch (Ii = It·Rt/Ri), power dissipation (P = V²/R), and an E12/E24 standard-value picker. 100% client-side.
Parkland Formula Calculator — 24-Hour Burn Fluid Resuscitation
Parkland formula (Baxter) calculator: calculate fluid needs for the first 24 hours of burn resuscitation — 4 mL × kg × %TBSA, 8-hour / 16-hour split, mL/hour rate, urine output target, child mode + rule of nines & Lund-Browder helper. Educational, not medical advice.
Parse JSON in SQL Generator
Interactive SQL query generator for querying and extracting JSON columns in MySQL, PostgreSQL, SQLite, and SQL Server.
Particle Velocity Calculator — Vibration PPV, Stokes Settling, Terminal & Wave
Calculate particle velocity 4 ways: USBM blasting ground-vibration peak particle velocity (PPV), Stokes settling velocity, general terminal velocity (drag iteration), and wave particle velocity v=2πfA. SI + imperial, 100% client-side.
Party Budget Planner — Birthday, Graduation, Cookout & Event Budget Calculator
Free party budget planner for birthdays, graduations, cookouts and game days: per-category budget builder, quantity-linked food & drink costing, guest-count scaler, budget-cap reverse mode and planned-vs-actual tracker. 100% client-side, no signup.
Party Drink Calculator — How Much Beer, Wine, Spirits, Punch, Soda & Ice for a Party
Free party drink calculator: plan exactly how much alcohol, punch, soda, water and ice your party needs. 6-mode lab — pace-based alcohol planner, punch batch scaler, soft-drink planner, ice calculator, keg planner and cost estimator. 100% client-side, no signup.
Party Food Calculator — How Much Food Per Person for a Party (8-Mode Lab)
Free party food quantity calculator: per-person food estimator, pizza calculator, pulled pork BBQ shrinkage, taco bar ingredients, appetizers per hour, catering portions, event presets and a shopping list + cost estimator. 100% client-side, no signup.
Passphrase Generator — Free Diceware Passphrase Generator (EFF Wordlist, Real Entropy)
Free diceware passphrase generator: memorable, high-entropy passphrases from the EFF wordlist (7776 words), picked with a bias-free CSPRNG. Real entropy calculation, crack-time estimates, physical-dice mode. 100% client-side — nothing leaves your browser.
Password Entropy Calculator — Bits of Entropy + Crack Time Estimates
Free password entropy calculator: measure password strength in bits (L × log2(N)), get honest crack-time estimates across 4 attack scenarios, charset presets, diceware passphrase entropy, and worked examples. 100% client-side — your password never leaves your device.
Password Leak Check
Check the security strength of your passwords locally.
Password Strength Checker — How Secure Is My Password?
Free password strength checker: instant 0–100 score with label, crack-time estimates across 3 attack scenarios, keyboard-walk and common-password detection (including leetspeak variants), specific improvement tips, and a transparent score breakdown. 100% client-side — your password never leaves your browser.
Patent Cost Lab — USPTO Patent Cost Calculator (2025 Fees) | nrtechstudio.com
Free USPTO patent cost calculator: 2025 fee schedule × large/small/micro entity, provisional vs utility comparator, maintenance fees, 20-year total cost, attorney ranges, and PCT international route estimator. Educational estimates — not legal advice.
Patio Size Calculator — 7 Ways to Size Your Patio
Patio size calculator: 7 modes — size by guests, check a size, furniture fit, fire pit zone, multi-zone layout, paver count, yard fit. Free, client-si
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.
Paver Calculator: How Many Pavers Do I Need? (Base, Sand & Cost)
Paver calculator: how many pavers do I need? Field + soldier-course border, base gravel, bedding & polymeric sand, pallets, cuts and full project
Paycheck Calculator & Net Salary Tax Suite
High-precision Paycheck Calculator, Net Salary Take-Home, W-2 & 1099 Self-Employed Tax Engine.
PayPal Fee & Payout Calculator
Free online PayPal fee calculator to compute merchant transaction deductions, international rates, and exact invoice totals to receive a desired net amount.
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.
Peak Flow Calculator — Predicted PEF, Asthma Zones & Diurnal Variability
Free peak flow calculator: predicted PEF from age, sex and height (Nunn & Gregg 1989), asthma action-plan zones from your personal best, diurnal varia
Peak to Peak Voltage Calculator
Convert peak-to-peak voltage (Vpp) to peak voltage (Vpeak) and RMS voltage (Vrms) for sine, square, and triangle waveforms, with DC offset and frequency/period tools.
Pearl Index Calculator — Measure Contraceptive Effectiveness
Free Pearl Index calculator: enter pregnancies and exposure to compute the Pearl Index (pregnancies per 100 woman-years). Includes perfect-use vs typi
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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.