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.
Caulk Calculator — Tubes, Coverage and Cost Estimator | nrtechstudio.com
Estimate caulk and sealant tubes, coverage per package, backer rod size and project cost from joint dimensions.
CC to Grams Converter: Volume to Mass Calculator with Density Table
Free online cc to grams converter and grams to cc converter. Enter a volume in cc, pick a substance density (water, flour, sugar, oil, honey, milk) or enter custom g/cc. Formula, conversion chart, and FAQ included.
cc to ml Converter: 1 cc = 1 ml Exact Conversion with Syringe Dosing Guide
Free cc to ml converter. 1 cc = 1 ml exactly. Convert cc to ml, ml to cc, liters, teaspoons, tablespoons, fluid ounces and cups, with syringe dosing examples and medical FAQs.
CCF to Therms Converter: Convert Natural Gas CCF to Therms
Free CCF to therms converter for natural gas bills. Convert CCF to therms (and back) with an adjustable conversion factor, estimate your gas bill, and convert to BTU, kWh, and MCF.
CD Calculator (Certificate of Deposit): Yield, Penalties & Ladder
Free CD calculator: compute certificate of deposit maturity value, early withdrawal penalties, compare 2 CDs, and build a 3/6/9/12-month CD ladder. 100% in the browser.
CDAI Calculator — Crohn's Disease Activity Index (Best 1976)
Free CDAI calculator: compute the Crohn's Disease Activity Index from the 8 weighted components of Best et al. (1976) — 7-day diary, extraintestinal c
Ceiling Fan Size Calculator — Blade Span, Downrod & CFM Sizer
What size ceiling fan for your room? Free blade-span chart by sq ft, downrod length, CFM efficiency & AC savings calculator — 7 modes in one tool.
Cell Dilution Calculator — C₁V₁=C₂V₂, Dilution Factor & Serial Planner
Free cell dilution calculator: compute stock volume with C1V1=C2V2, dilution factor, and plan exact serial dilutions step-by-step. 100% client-side, no data leaves your browser.
Cell Phone Plan Calculator — Compare Plans, Fees & Family Costs
Compare cell phone plans: carrier costs, taxes and fees by state, per-line family pricing, and buy-vs-carrier device math. Free tool.
Celsius to Fahrenheit Converter: °C to °F Calculator with Table and Formula - nrtechstudio.com
Free Celsius to Fahrenheit converter with a two-way calculator, conversion formula, quick reference table from -40 to 100°C, and common temperatures like body temperature and oven settings.
Centigrade to Celsius Converter: Same Scale, History and Chart
Centigrade to Celsius calculator: centigrade and Celsius are the same scale, so conversion is instant. Includes the 1948 history, conversion formulas to Fahrenheit and Kelvin, and a full centigrade to Celsius conversion chart.
Centimeter Converter: cm to Inches, Feet, Meters and More
Free centimeters to inches calculator and cm converter hub. Convert cm to inches, feet, meters, millimeters, kilometers, yards, and miles instantly. Includes quick conversion tables, TV screen size cm to inches, and height cm to feet charts.
Centor Score Calculator — McIsaac Modified Centor Score for Strep Pharyngitis
Free Centor score calculator with the McIsaac age modification: 4 clinical criteria (fever ≥38°C, no cough, tonsillar exudate, tender anterior cervica
Centrifugal Force Calculator - F = mv²/r Solver, RPM & g-Force
Free centrifugal force calculator: solve F = m·v²/r = m·ω²·r for force, mass, speed, or radius. Supports N/kN/lbf, RPM, rad/s, plus max safe RPM mode and g-force. 100% client-side.
Centrifuge Speed Calculator - RPM to RCF (×g) Converter
Free centrifuge speed calculator: convert RPM to RCF (×g), find the RPM for a target ×g, or solve for rotor radius. Uses RCF = 1.118×10⁻⁵ × r(cm) × RPM².
Cephalexin for Cats Dosage Calculator by Weight — mg Range Estimator, mL & FAQ
Free cephalexin for cats dosage calculator: enter your cat
Cephalexin for Dogs Dosage Calculator by Weight — mg Range Estimator, mL, Chewable Combos & FAQ
Free cephalexin for dogs dosage calculator: enter your dog
Cerebral Perfusion Pressure (CPP) Calculator — MAP − ICP | NR Tech Studio
Free cerebral perfusion pressure calculator: enter SBP, DBP and ICP to compute MAP and CPP (CPP = MAP − ICP), with BTF-based interpretation bands. Edu
CHA2DS2-VASc Score Calculator — AFib Stroke Risk Estimator (Educational) — NR Tech Studio
Free CHA2DS2-VASc calculator: estimate stroke risk in atrial fibrillation from 8 clinical factors, with live score, breakdown, interpretation table, and worked examples. Educational tool — not medical advice.
Chandelier Size Calculator — Diameter, Height & Hang Rules
What size chandelier for your room? Free 7-mode sizer: room diameter, dining table rules, hang height, chain drop, two-story foyer, island & lumens.
Character Frequency Counter — Analyze Character & Letter Frequency Online
Free character frequency counter. Count character occurrences, see letter frequency percentages, top words, and character distribution charts. 100% client-side.
UTF-8 Character Encoder & Text Sanitizer
Free online UTF-8 character encoder, Unicode inspector, and special characters remover. Convert unicode characters, remove special characters from string, and inspect byte encodings.
Character Count Counter – Word Tracker & Text Analyzer
Character count counter, character count tool, word count shortcut, text character counter, word occurrence count, char length counter, word count tracker, text length counter, ai word counter, string length checker, sentence character counter, average word length calculator, reading time calculator word count.
Character Name Generator Based on Personality & AI Fantasy Studio
Interactive character name generator based on personality and ai name generator fantasy for writers and RPG creators.
Characteristic Polynomial Calculator - 2×2 & 3×3 Matrices | nrtechstudio
Free characteristic polynomial calculator for 2×2 and 3×3 matrices. Computes det(A − λI), trace, determinant, and eigenvalues (roots of the characteristic equation) with step-by-step working.
Electric Charge Converter — Coulomb, mAh, Wh, Capacitor & Coulomb's Law | nrtechstudio
Free electric charge converter: coulombs to mAh/Ah, mAh↔Wh battery calculator, capacitor charge & energy (Q=CV, E=½CV²), RC time constant, Coulomb
Charles's Law Calculator - V₁/T₁ = V₂/T₂ Solver (Free)
Free Charles's law calculator: solve V₁/T₁ = V₂/T₂ for any missing variable. Volume in m³, L, mL or ft³; temperature in °C, °F or K (auto-converted to kelvin). Instant results with full unit conversio
Cheese Aging Calculator — How Long to Age Cheese (Free Planner)
Free cheese aging calculator: pick a style (cheddar, gouda, parmesan, brie, blue, swiss, camembert, monterey jack), choose an aging tier, and get your ready date, temperature & humidity targets, and a flavor timeline. 100% client-side, no signup.
Cheese Yield Calculator — How Much Milk to Make Cheese (Van Slyke)
Free cheese yield calculator: find out how much milk you need to make cheese — or how much cheese your milk makes. Van Slyke formula, cow/goat/sheep/buffalo milk presets, 19 cheese styles, both directions, metric & imperial.
Chess ELO Calculator — FIDE, USCF, Chess.com & Lichess Rating Change, Performance Rating, Target Planner
Free chess ELO calculator and rating suite: single-game ELO change (FIDE K=40/20/10, USCF, Chess.com, Lichess), tournament simulator, reverse target planner, FIDE performance rating (Rp = Ra + dp), initial rating for unrated players, win-probability explorer and honest rating converter with uncertainty intervals. 100% client-side.
Chi-Square Test Calculator — χ², p-Value, Cramér's V | NRTechStudio
Free chi-square test calculator: enter any r×c contingency table or goodness-of-fit data to get expected frequencies, χ² statistic, degrees of freedom, p-value, a significant-or-not verdict, Yates' correction for 2×2, and Cramér's V effect size.
Chicken Coop Calculator — Coop & Run Planner, Materials & Cost Estimator
Free chicken coop size calculator: coop + run space per bird (bantam, standard, heavy breeds, ducks), reverse capacity check, nesting box planner, roost & ventilation, flock starter, lumber materials takeoff and cost estimator. Metric/imperial. 100% private — runs in your browser.
Chicken Feed Calculator — Amount, Cost, Storage & Ration Mixer (Duck, Goat, Quail)
Free chicken feed calculator: daily feed per hen, flock feed planner, feed cost per month and per dozen eggs, bag planner, storage guide, and layer-mash + grain mixer. Duck, goat & quail included. 100% client-side.
Child BMI Calculator — CDC BMI-for-Age Percentile (Ages 2–20)
Free child BMI calculator: enter age, height and weight to get your child's BMI, CDC BMI-for-age percentile and weight category, plus parent guidance. Ages 2–20. Educational use.
Child Cost Calculator — USDA Cost of Raising a Child to 18 | nrtechstudio.com
Child cost calculator: estimate the cost of raising a child to 18 with USDA data — by income, age, region and family size, plus inflation projection.
Child-Pugh Score Calculator — Cirrhosis Severity (Class A/B/C)
Free Child-Pugh (Child-Turcotte-Pugh) score calculator. Enter bilirubin, albumin, INR, ascites and encephalopathy to get the 5–15 point total, Class A/B/C and published survival context. Educational tool — not medical advice.
Child Support Calculator — by State, Custody %, Canada & UK (Free Lab)
Free child support lab: US state estimator (income-shares, percentage & Melson models, TX/CA/WI/NY formulas), custody-time % calculator, shared-custody cross-credit, Canada federal tables (2025 & 2017), UK CMS formula, and arrears + interest estimator. 100% client-side.
Childcare Cost Calculator — Daycare vs Nanny vs Au Pair, Tax Savings & Break-Even Lab
Free childcare cost lab: compare daycare center vs home daycare vs nanny vs au pair side-by-side, estimate costs by state/ZIP, UK 30 free hours, Australia & Canada, Dependent Care FSA + Child and Dependent Care Tax Credit math, work-vs-stay-home break-even, and multi-child pricing. 100% client-side.
Chmod Calculator & Linux Permissions Tool
Free online Linux Chmod calculator to convert between numeric octal permissions (777, 755, 644) and symbolic rwx notation with instant command generation.
Cholesterol Units Converter — mg/dL ↔ mmol/L (Cholesterol & Triglycerides)
Free cholesterol units converter: convert total, LDL and HDL cholesterol between mg/dL and mmol/L (divide by 38.67) and triglycerides (divide by 88.57), with general reference ranges. 100% in-browser. Estimates only — not medical advice.
Chord Lab — Chord Construction Calculator, Inversions, Capo Transpose Tools
Free chord construction lab: type any chord (Cmaj7, F#m7b5, Bb13) to get correctly spelled notes, intervals, inversions, piano & guitar voicings with audio playback. Plus note frequencies, capo/transpose calculators, transposing-instrument converter, progression builder and fret-position calculator. 100% client-side.
Cider Making Calculator Suite — ABV, Chaptalization, Backsweetening, Priming Sugar & Stabilizer (Free)
Free cider making calculator suite: cider ABV calculator (standard + high-gravity ice cider formulas), chaptalization sugar to target ABV, backsweetening to target gravity, Campden/sulfite & potassium sorbate stabilizer dosing, bottle carbonation & priming sugar with per-bottle dosing, juice blending and dilution. 100% client-side, no signup.
Classical Cipher Lab — Caesar, ROT13 & Vigenère Decoder/Encoder Online
Free online classical cipher lab: ROT13/ROT5/ROT47 encoder-decoder, Caesar cipher encoder/decoder with 26-shift brute-force solver and frequency analysis, Vigenère encoder/decoder with key-length estimation and chi-square key recovery, plus an interactive tabula recta. 100% client-side — nothing ever leaves your browser.
Circle Area & Circumference Calculator
Engineering-grade Circle Area Calculator, Radius & Circumference Solver, Sector Angle Calc, and Circle Equation Tool.
Circle Formula & Geometry Calculator
Interactive circle formula calculator, circumference solver, area o f circle calculator, square footage of a circle, and exact in terms of pi output.
Circle Skirt Calculator — Waist Radius, Fabric Yardage & Pattern Diagram
Free circle skirt calculator: enter waist + skirt length to get the waist radius for full, 3/4, half or quarter circle skirts, fabric yardage for 45/60 in widths, and a labeled pattern diagram.
Uniform Circular Motion Calculator — v, ω, r, T, f, a_c | NR Tech Studio
Uniform circular motion kinematics calculator: solve for linear velocity (v), angular velocity (ω), radius (r), period (T), frequency (f), and centripetal acceleration (a_c). Supports RPM, km/h, cm, ms. 100% offline.
Circle Dimension Hub: Circumference to Radius, Diameter & Area Calculator
All-pairs circle dimension hub: enter circumference, diameter, radius, or area — the other three are computed automatically (C/D/r/A) + SVG diagram. Free, no server.
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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.