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.
Net Worth Calculator & Tracker — Free, No Signup | nrtechstudio
Free net worth calculator with detailed asset & debt breakdown, private local tracker with month-over-month trends, percentile-by-age benchmark, and a 5-year what-if projector. No signup — your data never leaves your browser.
New York Overtime Pay Calculator — 1.5× for Hours Over 40
Calculate New York overtime pay: 1.5× the regular rate for hours over 40/week + check your rate against the NYC $17.00, Long Island & Westchester $17.00, and rest of NY $16.00 minimum wages (verified Oct 9, 2026). Hourly mode, salary→weekly mode, comparator, FAQ. Free.
Newborn Hyperbilirubinemia Assessment — Bhutani Nomogram Calculator | nrtechstudio
Free newborn hyperbilirubinemia risk assessment: plot total serum bilirubin by age in hours on the Bhutani nomogram (40th/75th/95th percentiles), get
Newline to Comma Converter
Fast client-side line break to comma tool, text delimiter replacer, and SQL IN clause generator.
Newton to Joules Calculator: Force x Distance to Energy (3 Modes)
Convert newtons to joules honestly: energy = force x distance. 3 modes: force+distance to energy, energy+distance to force, energy+force to distance. Free, no signup.
Newton's Law of Cooling Calculator — T(t), Cooling Coefficient k & Time to Target
Free Newton's law of cooling calculator: T(t) = Ts + (T0 − Ts)·e^(−k·t). Predict temperature after a time, fit the cooling coefficient k from two meas
Next.js Template & Starter Generator
Interactive Next.js starter template generator for SaaS apps, landing pages, ecommerce storefronts, and blog CMS templates.
Next.js vs React Comparison & Decision Tool
Interactive decision matrix comparing Next.js vs React, analyzing difference between react and nextjs, versions, and framework features.
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.
Nickels to Dollars Calculator | US Coin Converter
Convert nickels to dollars and dollars to nickels instantly. 1 nickel = $0.05 exactly. Includes every US coin, mixed-coin totals, bank roll values, and a change breakdown.
Nightstand Size Calculator — Height, Width & Depth for Your Bed
Nightstand size guide: match height to your mattress, width to your bed size, plus depth and gap rules. Free calculator, imperial + metric.
NIH Stroke Scale (NIHSS) Calculator — 15-Item Scorer, 0–42 Severity Bands & UN Handling | nrtechstudio
Free NIH Stroke Scale calculator (NINDS, Brott & Adams 1989): interactive 15-item NIHSS scorer with examination instructions per item, total 0–42,
Nitrox Calculator & Planning Lab — MOD, EAD, Best Mix, ppO2, CNS%, OTU
Free nitrox diving calculator suite: MOD calculator, EAD, best mix, ppO2 at depth, CNS% oxygen toxicity clock, OTU tracking, nitrox blending math and NDL estimator. 100% client-side.
Nm to ft lb Converter: Newton Meters to Foot Pounds Torque
Convert newton meters (Nm) to foot pounds (ft lb) and back, live. Exact SI factor 1 ft lb = 1.3558179483314004 Nm. Multi-unit torque panel, quick tables, worked examples.
Nanometer to Meter Converter (nm to m)
Free nm to m converter: convert nanometers to meters instantly, both directions, plus micrometer, millimeter and kilometer. Exact definition 1 nm = 1e-9 m, with show-your-work steps, quick table and FAQs.
NNT Calculator — Number Needed to Treat (Laupacis 1988)
Free NNT calculator: compute number needed to treat (NNT) and number needed to harm (NNH) from control and experimental event rates, with ARR, RRR, 95
Noise Figure Calculator — dB ↔ Linear, Friis Cascade & Noise Temperature | nrtechstudio.com
Free noise figure calculator: convert NF between dB and linear, compute cascaded noise figure with the Friis formula (up to 6 stages, per-stage contri
NOPAT Calculator — Net Operating Profit After Tax
NOPAT calculator (net operating profit after tax): compute NOPAT from EBIT × (1−tax rate) or from revenue−COGS−expense components, compare 2 companies, and simulate NOPAT targets. 100% free in your browser.
Normal Distribution Calculator – Standard Score & Probability
Normal distribution calculator, standard score calculator, z score into percentile, z score cal, p from z score, z score range, standard distribution calculator, z star calculator, standard normal cdf calculator, calculate percentile from mean and standard deviation calculator.
Normal Force Calculator — Flat, Inclined Plane & Elevator
Free normal force calculator: compute N = m·g (flat plane), N = m·g·cos θ (inclined plane), angled push/pull force, and N = m·(g+a) in an accelerating elevator. SVG force diagram, worked steps, kg/g/lb and N/kN/lbf units. 100% client-side.
Net Promoter Score (NPS) Calculator — Calculate NPS 0–10
Free Net Promoter Score (NPS) calculator: compute NPS from 0–10 survey scores, compare two periods, and simulate what's needed to reach a target NPS. 100% runs in the browser.
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
NSFR Calculator (Net Stable Funding Ratio)
Basel III NSFR (net stable funding ratio) calculator: compute the net stable funding ratio from ASF/RSF components, view standard factor tables, compare 2 banks, and simulate the 100% NSFR target.
Nth Root Calculator — Cube Root, Fourth Root, Fifth Root & Any n
Free nth root calculator: square root, cube root, fourth root, fifth root or any custom n. Shows step-by-step work, detects perfect powers exactly, and handles negative numbers honestly.
Number Base Converter — Binary, Octal, Decimal, Hex & Any Base (2–36) | nrtechstudio.com
Free number base converter: binary, octal, decimal, hexadecimal and any base 2–36 with step-by-step solutions. Bitwise calculator, two
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,
Number Density Calculator | nrtechstudio.com
Free number density calculator: n = N/V, n = p/(kB·T) for ideal gases (Pa/kPa/bar/atm/psi/torr, °C/K/°F), or n = Z·ρ·NA/M from mass density. Loschmidt
Number List Generator
Free online number list generator. Generate list of numbers, number sequence generator, create number list, list of numbers from 1 to 100, generate consecutive numbers, number range generator, zero padded number list.
Tool - Number of Days Between Two Dates Calculator
High-precision date duration calculator to compute calendar days, business days, workdays, weekends, date addition, age, and milestone spans between any two dates.
Weeks Between Now & End of Year – Date & Calendar Calculator
Number of weeks between now and end of year, add subtract dates, compute days between two dates, days from today calculator, time till calculator, weeks since calculator, compute number of days between two dates, day calculator from date to date, days left calculator, date subtraction calculator, subtract 2 dates, dating days calculator, calendar calculator between dates, date to date calendar calculator, countdown by weeks, date to date month calculator, how much time between dates, how many weekdays between, calculation between 2 dates, calendar calculator number of days, date gap calculator, count number of days from date, date calculator calculator, days calculator without weekends, time difference calculator between two dates, minus days calculator, calendaring calculator.
Nursery Size Calculator — 7 Ways to Plan the Perfect Nursery Room
Nursery size calculator: crib footprint + 36-inch clearance, 10x10 room rule, glider recline space, changing table zones and toddler-bed growth plan.
Nusselt Number Calculator — Dittus–Boelter, Flat Plate & Nu = hL/k Solver
Free Nusselt number calculator: Nu = h·L/k in 4 solve directions, Dittus–Boelter turbulent pipe correlation (Nu = 0.023·Re^0.8·Pr^n) with h back-calcu
Oblique Shock Calculator — θ–β–M Solver, Weak & Strong Shock, θ_max Chart | nrtechstudio.com
Free oblique shock calculator: solve the θ–β–M relation for shock angle β from Mach number and deflection angle, get weak and strong shock solutions,
Occupancy Rate Calculator — Hotel, Boarding House & Property
Calculate occupancy rate for hotels, boarding houses, and apartments: basic occupancy, room nights and RevPAR, two-period comparator, and occupancy target solver.
Octal to IP Converter
Enterprise-grade Octal to IPv4 converter, IP address deobfuscator, and SSRF security analyzer with 100% SEMrush keyword optimization.
Office Moving Cost Calculator — Commercial Move Estimator (per Sq Ft, per Employee, Downtime)
Free office moving cost calculator: estimate commercial moves per square foot ($1–$5/sq ft), per employee ($50–$250), downtime cost ($200–$400/employee/day), IT & after-hours premiums, and office size presets. Planning ranges, not quotes.
Omega-3 for Dogs Calculator — EPA+DHA Dose by Weight, Source Compare & Cost
Free omega-3 (EPA+DHA) calculator for dogs: estimated daily dose range by weight, product label decoder, fish oil vs krill vs algal comparison, monthly cost, and vet-verified safety limits. Estimate o
One Rep Max Calculator (1RM) — 7 Formulas Compared Side-by-Side
Free online one rep max calculator (1RM calculator) that runs 7 proven formulas — Epley, Brzycki, Lombardi, O'Conner, Wathan, Lander, Mayhew — side-by-side with agreement analysis, %1RM table, and a warmup set calculator. 100% client-side, no signup.
Online Sql Compiler
Open Channel Flow Calculator — Manning Equation (Rectangular, Trapezoidal, Triangular, Circular)
Free open channel flow calculator using Manning's equation. Rectangular, trapezoidal, triangular & circular channels, normal depth solver, Froude number, and a Manning's n roughness table.
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.
Operating Cash Flow (OCF) Calculator — Calculate Operating Cash Flow
Free operating cash flow (OCF) calculator: compute operating cash flow via the indirect method from net income, working capital, margin, and OCF target solver.
OPML Generator
Professional OPML 2.0 Subscription List Generator, RSS OPML Feed Builder, and Podcast Outline Creator with 100% SEMrush keyword optimization.
Optical Density Calculator — OD ↔ Transmittance, Beer–Lambert, ND Filters
Free optical density calculator: convert OD ↔ transmittance, solve the Beer–Lambert law (A = ε·c·l) 4 ways, and total OD of stacked ND filters. 100% runs in the browser.
Orbital Period Calculator — Kepler's Third Law, LEO/GEO & Altitude Solver
Free orbital period calculator: T = 2π√(a³/μ) with presets for the Sun, Earth, Moon, Mars and Jupiter. Solve period from semi-major axis or altitude,
Orbital Velocity Calculator — v = √(μ/r), Vis-Viva & First Cosmic Velocity
Free orbital velocity calculator: v = √(μ/r) for circular orbits, vis-viva v = √(μ(2/r − 1/a)) for elliptical orbits, velocity from altitude with esca
Java org.json Code Generator
Interactive Java org.json snippet generator for JSONObject, JSONArray, XML conversion, and Maven dependency configuration.
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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.