Free Converters Tools & Calculators
Browse 349+ free interactive converters calculators, estimators, and utilities. 100% free, private, and runs directly in your browser without signup.
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.
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.
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
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
Octal to IP Converter
Enterprise-grade Octal to IPv4 converter, IP address deobfuscator, and SSRF security analyzer 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.
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.
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.
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
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
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
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.
Percent to Ratio Calculator: Convert % to Ratio, Ratio to % and Slope Grade
Free percent to ratio calculator with exact integer math. Convert percent to ratio (25% to 1:3), ratio to percent (1:3 to 25%), and slope percent to ratio grade (10% to 1:10). Includes common percent table 1 to 99 and worked examples.
Percent to Total Calculator: Find the Total, Part, or Percent - nrtechstudio
Free percent to total calculator: X is P% of the total, find the total (e.g. 45 is 30% -> 150). Also solves P% of total and X of total as percent. Exact fractions, show-your-work steps, 100% client-side.
Period to Frequency Calculator | T = 1/f, Angular Frequency and Wavelength
Free two-way period to frequency calculator: f = 1/T and T = 1/f with s, ms, us, ns and Hz, kHz, MHz, GHz units, plus angular frequency (omega = 2 pi f) and vacuum wavelength (lambda = c/f). 100% client-side.
P/E2 Ratio Calculator — Progesterone to Estradiol Ratio + Unit Converter
Calculate your progesterone-to-estradiol (P/E2) ratio with automatic unit conversion (ng/mL ↔ nmol/L, pg/mL ↔ pmol/L). IVF trigger-day and mid-luteal
Pint to Pound Converter: Volume to Weight via Density
Convert pints to pounds and pounds to pints using density. Supports US liquid pint, US dry pint, and imperial pint with presets for water, milk, oil, honey, flour, and sugar.
Pixels Inches Conversion – DPI, PPI & Print Resolution
Pixels inches conversion, translate pixels into inches, px inches conversion, converter px, in to px conversion, dpi to px conversion.
Pool Salt Calculator
Pool salt calculator: how much salt to add to a saltwater pool in lb, kg and 40-lb bags, salt level check, salt cell sizing guidance and cost estimator.
Pool Size Calculator — 7 Ways to Size Your Swimming Pool
Free pool size calculator with 7 modes: family, lap, compact and kids sizing, depth planner, deck space, setbacks and yard-fit check. 100% client-side
Potting Bench Size Calculator — Height, Width, Materials, Sink & Cost | nrtechstudio.com
Potting bench size calculator: height matched to you, width from pots and soil bags, shelf storage, sink cutout, lumber list, balcony version and cost
Pounds to Grams Converter (lb to g) - Exact 453.59237
Convert pounds to grams and grams to pounds with the exact definition: 1 lb = 453.59237 g. Free two-way lb to g calculator with precision control, conversion table, and worked examples.
Basic Present Value Calculator — Single Lump-Sum PV
Free present value calculator (basic): discount one future lump sum to today's money with PV = FV/(1+r)^n, discount factor, and year-by-year schedule.
Present Value of Cash Flows Calculator — PV of Uneven Streams
Free present value of cash flows calculator: discount an uneven stream of future cash flows to today's dollars, with a per-period PV table.
Price Per Liter to Price Per Gallon Calculator
Convert fuel price per liter to price per US gallon and imperial gallon, compare two fuel prices, and calculate fuel cost per 100 km or 100 miles. Free calculator.
Price Per Sqft Calculator — $/Sq Ft, Compare & Convert
Free price per sqft calculator: $/sq ft from price and area,
Projector Throw Distance Calculator & Screen Size Planner (Model-Agnostic) | Projector Throw Lab
Free model-agnostic projector throw calculator: throw ratio, throw distance, screen size, short-throw & UST mode, zoom-range visualizer, screen-size converter, and brightness sanity check. 100% client-side.
PSI Conversion Calculator (PSI to Bar, kPa, MPa, ATM)
Free psi conversion calculator. Convert psi to bar, kPa, MPa, ksi, atm, inHg, mmHg, torr, psf and kg/cm2, both directions. Exact constant: 1 psi = 6,894.757293168 Pa. Includes conversion charts, worked examples and FAQ.
PSI to GPM Calculator: Orifice Flow from Pressure Drop
Free PSI to GPM calculator. Convert pressure drop (PSI) to water flow rate (GPM) through an orifice or nozzle: GPM = 29.81 x Cd x d^2 x sqrt(dP). Includes reverse mode, discharge coefficients, orifice table, worked examples and FAQ.
PSIG to PSIA Conversion Calculator
Convert psig to psia and back. psia = psig + 14.6959. Enter your actual barometric pressure for precision, plus vacuum (psiv) conversion, worked examples, and 16 FAQs.
PT to PX Converter & EM to Pixels Studio
Interactive pt to px converter, 1em to px, 1 em in px, and convert em to pixels CSS typography unit tool.
Punycode Converter — Unicode ↔ Punycode (IDN) with Homograph Phishing Detector
Free online Punycode converter: Unicode to Punycode and Punycode to Unicode per RFC 3492, full domain & URL mode, batch conversion, plus an IDN homograph phishing detector. 100% client-side — nothing leaves your browser.
Python Pad String with Spaces & YAML Parser
Interactive developer tool for Python string padding, YAML parser, YAML formatter online, JSON to YAML converter, and HTML escape utilities.
Quarts to Pounds Converter (qt to lb via Density)
Convert quarts to pounds and pounds to quarts with density. US liquid, US dry, and imperial quarts. Presets for water, milk, oil, honey, flour, sugar plus custom density.
Lettering Text Generator & Random Number Generator 1-150
Free online lettering text generator, script text generator, and random number generator 1-150. Convert text into cool Unicode fonts, cursive script, block text, and pick random numbers.
Random RGB Gen
Engineering-grade Random RGB Color Generator, Color Palette Randomizer, Hex Code Chooser, and Scheme Creator.
Relative Humidity Calculator — RH from Temperature & Dew Point
Free relative humidity calculator: compute RH from air temperature and dew point (Magnus formula), from absolute humidity, invert to find the dew poin
Reverse Text Generator & Upside Down Flip
Free high-performance reverse text generator, backwards text maker, and upside down text converter.
RMS to Watts Converter — Vrms to Watts Calculator (Audio & AC Power)
Convert RMS voltage to watts: P = Vrms²/R for speakers and resistive loads, P = Vrms × Irms × PF for AC circuits, plus reverse solve (find R or Vrms from watts) and audio power presets.
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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.