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.
Calorie Density Calculator: Calories per Gram of Any Food | nrtechstudio.com
Free calorie density calculator: enter calories and weight to get calories per gram, the Volumetrics category (very low, low, medium, high), compare t
Calories Burned Calculator — MET-Based Activity Calorie Burn
Free calories burned calculator: pick an activity, enter your weight and duration, and get an estimate via MET values from the 2011 Compendium of Physical Activities. Compare two activities side by side or plan a multi-activity session.
Calories Burned Hiking Calculator — Elevation, Pack Weight & Terrain
Estimate calories burned hiking from body weight, pack weight, distance, elevation gain, duration and terrain. Uses the published Pandolf (1977) metab
Calorimetry Calculator (q = m·c·ΔT) & Mixture Temperature — nrtechstudio.com
Free calorimetry calculator: compute heat q = m·c·ΔT (4 variables), thermal equilibrium temperature of 2–3 bodies (heat-exchange principle), and heating-time estimates from power. 100% client-side.
Camp Stove Fuel Calculator — How Much Fuel for Backpacking (Free)
Free camp stove fuel calculator: how much fuel to bring backpacking. Canister (isobutane), alcohol, Esbit, white gas & wood stoves — wind, altitude, simmering, snow-melting, partial-canister checker & 100g vs 230g vs 450g recommender. 100% client-side, no signup.
Canadian Mortgage Calculator — Semi-Annual Compounding, B-20 Stress Test
Canadian mortgage calculator with correct semi-annual posted-rate conversion, rate converter, Canada vs US comparator, and OSFI B-20 stress test. Educational estimate, not financial advice.
Candela to Lux Converter — Inverse-Square Law Calculator | nrtechstudio
Free candela to lux converter with the inverse-square law: convert candela ↔ lux at any distance, candela ↔ lumens via beam angle, and lux ↔ lumens via area. Worked examples, formulas, and honest limitations. 100% client-side.
Candle Cost Calculator — COGS & Pricing Suite for Candle Makers
Free candle cost calculator: build your true cost per candle from purchase prices, add labor & overhead, price by margin, markup, wholesale 2x / retail 4x, estimate platform fees and find your break-even. 14 currencies. 100% client-side, no signup.
Candle Fragrance Load Calculator & Wax Suite — Fragrance Oil, Wax Amount, Batch Planner
Free candle fragrance & wax calculator suite: fragrance load calculator (% of wax vs % of finished batch), wax amount from container volume, wax-type database (soy, paraffin, beeswax, coconut max loads), batch scaler, reverse planner, g↔ml converter, wax melt lab, and melt/pour/cure reference tables. Metric + imperial. 100% client-side.
Cap Rate & Cash-on-Cash Return Calculator for Rental Property
Compute cap rate, cash-on-cash return, and rental property NOI in one tool. Educational estimate — not investment advice.
Capacitive Reactance Calculator (Xc) — Solver, Series/Parallel & RC Impedance
Free capacitive reactance calculator: compute Xc = 1/(2πfC), 3-variable solver (Xc/f/C), series & parallel capacitors, and series RC impedance + phase angle. 100% offline.
Capacitive Transformerless Power Supply Calculator — Capacitive Dropper
Size the series X2 capacitor (Xc dropper) for a transformerless power supply: required C, zener current, inrush resistor, and bleeder. 100% client-side. WARNING: not isolated from mains.
Capacitor Energy Storage Calculator — E = 1/2 CV^2 (Joules, Wh, Charge) | nrtechstudio.com
Free capacitor energy calculator: enter capacitance & voltage to get the energy stored in joules and watt-hours plus the charge in coulombs. Reverse solvers find C or V from a target energy, with a battery comparison and high-voltage safety notes. 100% client-side, no sign-up.
Capacitor Size Calculator for Motors — Start & Run Capacitors
Free motor capacitor size calculator: find recommended start capacitor (µF) and run capacitor (µF) by motor HP/kW, voltage and phase. Includes run capacitor uf chart per HP, start capacitor sizing, and safe replacement guidance.
Capital Gains Yield Calculator — Stock Price Return + Dividends
Compute capital gains yield (P1-P0)/P0, dividend yield, and total stock return. With visual breakdown and annualization from the holding period.
Car Affordability Calculator — How Much Car Can I Afford?
Free car affordability calculator: enter your income and it works backwards to the maximum car price you can afford, with the 20/4/10 rule, ownership costs, and total cost of ownership.
Car Crash Force Calculator — Impact Force, G-Force & Crash Energy | nrtechstudio.com
Free car crash force calculator: enter vehicle mass, speed and crumple-zone stopping distance to get impact force (N, kN), deceleration in g-force, kinetic energy dissipated and equivalent drop height. Pure physics, 100% in-browser.
Car Depreciation Calculator — Estimate Your Car's Future Value
Free car depreciation calculator: estimate your car's value year by year for up to 10 years using typical depreciation curves. Choose a vehicle category preset (luxury, sedan, SUV, truck) or set your own annual rates.
Car Interest Calculator — Total Interest Cost, Rate & Term Comparison
Free car interest calculator: total interest on a car loan, year-by-year interest breakdown, and side-by-side comparison of rate, term, and down-payment scenarios. 100% client-side.
Car Jump Distance Calculator — Ramp Projectile Physics & Stunts
Compute car jump distance from a ramp (projectile motion): speed, ramp angle, launch height. Plus inverse solver: speed needed for a target distance. 100% client-side.
Car Loan Calculator — Monthly Payment, Total Interest & Amortization Schedule
Free car loan calculator: estimate your monthly auto loan payment from price, down payment, trade-in, sales tax, fees, APR and term. See total interest, total cost, year-by-year and monthly amortization schedule, and compare up to 3 loan scenarios side by side.
Car Loan EMI Calculator India — EMI, Flat vs Reducing Rate & Prepayment
Free car loan EMI calculator for India. On-road price (ex-showroom + RTO + insurance), down payment, reducing-balance rate, tenure 12–84 months → monthly EMI in ₹ with lakh formatting, flat-vs-reducing converter, prepayment simulator, amortization schedule + CSV. 100% client-side.
Car Maintenance Schedule Generator — Service Due Calculator by Mileage
Free car maintenance schedule generator: enter your odometer and get exactly what service is due now, what's next, predicted dates, typical intervals (normal vs severe), EV/diesel/hybrid modes, and editable cost estimates. 100% client-side, no signup.
Car Refinance Calculator — Comparator, Break-Even, and Term Trap
Car refinance calculator: compare old vs new payments, compute refinance cost break-even, net savings, and the term-extension trap.
Carb Calculator — How Many Carbs Per Day?
Free carb calculator: convert your calorie target to daily carb grams (by %, g/kg, or grams), see net carbs, per-meal breakdown, low-carb and keto thresholds. Educational tool.
Carburetor CFM Calculator — Size Your Carb Right | nrtechstudio.com
Free carburetor CFM calculator: enter engine displacement (CID or cc), max RPM and volumetric efficiency to get required CFM. Includes small block & big block sizing chart, 2-barrel vs 4-barrel conversion, and tips to avoid an oversized carb. 100% in-browser, no sign-up.
Cardiac Index Calculator — CI = CO / BSA
Free cardiac index calculator: enter cardiac output plus weight and height to get BSA (DuBois or Mosteller) and cardiac index in L/min/m², with normal
Cargo.toml Generator — Create & Make Rust Manifest Online
Free online Cargo.toml generator: package metadata, dependencies, features, target cfg, profiles and workspace for Rust projects.
Carnot Efficiency Calculator — Theoretical Limit of Heat Engines
Free Carnot efficiency calculator: η = 1 − Tc/Th (absolute Kelvin temperature). Compute the maximum efficiency, the required hot-reservoir temperature, or the allowed cold-reservoir temperature. Gasoline engine & steam power plant presets.
Carpet Calculator — How Much Carpet Do I Need? (Roll, Seam & Stairs)
Free carpet calculator: find exactly how much carpet you need. Roll-width optimizer (12ft/15ft/4m/5m), seam planner, stairs mode, pattern repeat matching, waste %, cost estimator. Metric + imperial + gaj.
Carport Size Calculator — Find the Right Carport Dimensions
Free carport size calculator with 7 modes: vehicles-to-size sizer, capacity checker, standard size charts, door clearance, height check and fit valida
Cartesian to Polar Converter — Two-Way (x,y) ↔ (r,θ) Conversion | nrtechstudio.com
Free two-way Cartesian to Polar converter: convert (x,y) to (r,θ) with r=√(x²+y²) and quadrant-aware θ=atan2(y,x), or (r,θ) back to (x,y). Includes an interactive vector diagram, calculation steps, and worked examples.
Case Converter — UPPERCASE, lowercase, Title Case, camelCase, snake_case & More
Free online case converter: type once and get UPPERCASE, lowercase, Title Case, Sentence case, camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE, aLtErNaTiNg and InVeRsE instantly. 100% in-browser, private, no sign-up.
Cash Back vs Low Interest Calculator — Which Saves More?
Compare cashback/rebate + market-rate offers vs low/0% promo-rate offers for auto financing. Calculate total cost, find the break-even rebate, and view the sensitivity table.
Cash Conversion Cycle Calculator (CCC = DIO + DSO − DPO)
Free cash conversion cycle calculator: enter inventory, receivables, payables, COGS and revenue to get CCC, DIO, DSO and DPO with benchmarks, a what-if simulator and a cash-flow timeline. 100% client-side.
Cash Flow to Debt Ratio Calculator — Measure Debt-Paying Ability from Cash Flow
Calculate the cash flow to debt ratio: operating cash flow (OCF) or free cash flow (FCF) divided by total debt. Interpretation bands, what-if simulation for reducing debt / raising cash flow, examples, and FAQ.
Cash Ratio Calculator — Cash Liquidity Ratio
Calculate the cash ratio (cash + cash equivalents ÷ current liabilities), compare against quick ratio & current ratio, run what-if simulations, and interpret general guidance bands. 100% in the browser.
Cat Benadryl Dosage Calculator by Weight — Diphenhydramine mg, mL & Tablet Guide
Free cat Benadryl dosage calculator: enter your cat
Cat BMI Calculator — Feline Body Condition Score (BCS 1–9)
Free cat BMI calculator: estimate your cat
Cat Calorie Calculator — Daily kcal Needs for Cats | nrtechstudio.com
Free cat calorie calculator: find your cat
Cat Chocolate Toxicity Calculator — Theobromine Dose by Cat Weight | nrtechstudio
Free cat chocolate toxicity calculator: enter your cat's weight and the type and amount of chocolate to estimate the theobromine dose in mg/kg, with risk zones and emergency guidance. Estimate only —
Cat Pregnancy Calculator — Due Date, Week-by-Week Timeline & Labor Signs
Free cat pregnancy calculator: enter the mating date and get a 63–65 day due-date window, a week-by-week feline gestation timeline, signs of labor, a kittening checklist, and calendar reminders. 100%
Cat Quality of Life Calculator — HHHHHMM Scale for Cats
Free cat quality of life calculator using the HHHHHMM scale (Hurt, Hunger, Hydration, Hygiene, Happiness, Mobility, More good days), adapted for cats: hiding, grooming, litter box use. Score 1-10 per
Catculator: Cat Age Calculator — Cat Years to Human Years
Free Catculator: convert cat years to human years (and back) with month-level precision. Year 1 = 15, year 2 = 24, then +4/year. Life stages, interactive age chart, birthday countdown. 100% client-side.
Tool - Custom ERP Software & ROI Architecture Estimator
Interactive enterprise resource planning (ERP) calculator, custom ERP development cost estimator, and cloud-based ERP solutions architecture planner.
Software Development & Enterprise Engineering Estimator
Interactive software development cost & scope estimator, tech stack architecture planner, enterprise application development roadmap builder, and team velocity calculator.
Catenary Curve Calculator — Cable Sag, Length & Tension | nrtechstudio
Catenary curve calculator y = a·cosh(x/a): compute parameter a, cable length, sag, and horizontal tension T₀ = w·a from span + sag or span + cable length. Newton solver, SVG plot, point table.
Cattle Per Acre Calculator: Stocking Rate, Carrying Capacity & AUM | nrtechstudio
Free cattle stocking rate calculator: enter acres, forage yield, cow weight and grazing days to get carrying capacity (cows per acre), acres per cow, and total AUM.
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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.