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.
Enigma Machine Simulator (M3) — Free Online Enigma Encoder & Decoder
Free online Enigma M3 machine simulator: historically accurate rotors I–VIII, ring settings, plugboard and double-stepping, with live signal-path visualization. Encrypt & decrypt Enigma messages in your browser — no data leaves your device.
Enterprise Resource Planning Software Guide & Planner
Interactive enterprise resource planning software architecture planner, module cost estimator, top ERP platforms comparison, and small business readiness assessment.
Enterprise Value (EV) Calculator — EV Formula from Components
Compute enterprise value from its components: market cap + total debt − cash and cash equivalents. Includes a reverse solver, an EV-to-equity-value bridge waterfall, and a two-company comparator.
Enthalpy Calculator (H = U + PV, ΔH, Hess’s Law) — nrtechstudio
Complete enthalpy calculator: H = U + PV, ΔH = ΔU + PΔV, Hess’s law with formation-enthalpy table, sensible enthalpy m·c·ΔT, latent enthalpy m·L, molar & specific enthalpy, plus an energy unit converter.
EOQ (Economic Order Quantity) Calculator: Formula, Examples & Reorder Point
Compute EOQ (economic order quantity) with the √(2DS/H) formula: optimal order quantity, order frequency, interval, total cost, reverse solver, reorder point + safety stock, and a 2-scenario comparator.
EORTC Bladder Cancer Risk Calculator (NMIBC) — Recurrence & Progression | nrtechstudio.com
Free EORTC bladder cancer risk calculator for non-muscle-invasive bladder cancer (NMIBC). Computes recurrence (0–17) and progression (0–23) scores fro
Absolute Eosinophil Count (AEC) Calculator — Free Lab Tool
Free absolute eosinophil count (AEC) calculator: enter your total WBC count and eosinophil percentage to get AEC in x10^9/L and cells per microliter,
EPDS Calculator — Edinburgh Postnatal Depression Scale (Free Screening)
Free EPDS calculator: answer the 10 validated Edinburgh Postnatal Depression Scale questions, get your 0–30 score, cutoff band (10/13) and next-step g
EPF Calculator — India & Malaysia (KWSP) Retirement Fund Projection
Free EPF calculator: Employees’ Provident Fund balance projection for India (EPFO) & Malaysia (KWSP), target-based contribution solver, and 2-scenario comparison. In English.
Epoxy Calculator
Free epoxy calculator: volume, mix ratio, pour planner and cost.
EPS Calculator — Earnings Per Share (Basic, Diluted, P/E, YoY Growth)
Free EPS calculator: basic earnings per share, time-weighted shares, diluted EPS via the treasury stock method, P/E ratio, and year-over-year EPS growth — with step-by-step workings.
Epworth Sleepiness Scale (ESS) Calculator — Free Daytime Sleepiness Test
Free Epworth Sleepiness Scale (ESS) calculator. Answer the 8-question Johns (1991) questionnaire, get your 0–24 score and normal/mild/moderate/severe
EQ Frequency Chart Mixing Guide — Interactive (20 Hz–20 kHz)
Interactive EQ frequency chart for mixing: hover the 20 Hz–20 kHz spectrum to identify any note and EQ zone, explore 16 instruments (kick, snare, vocals, guitars, piano, strings, brass…) with fundamental ranges, sweet spots, cut zones and EQ moves, a frequency–note converter and a printable cheat sheet. 100% client-side.
Equivalent Interest Rate Calculator — Convert Between Compounding Frequencies
Free equivalent interest rate calculator: convert nominal rates between compounding frequencies (monthly, quarterly, annual, continuous), nominal ↔ EAR, reverse solver, and a full conversion table.
Er Diagram Generator
Erg Calculator — Concept2 Pace, Watts & Calories
Convert Concept2 rowing ergometer pace per 500m to watts and calories per hour with the official PM monitor formulas.
EROA Calculator — Effective Regurgitant Orifice Area (PISA Method)
Calculate effective regurgitant orifice area (EROA) from PISA measurements: EROA = (2 x pi x r squared x V_aliasing) / V_max. Includes ASE 2017 severi
ERP System Meaning – Enterprise Resource Planning Guide
Comprehensive ERP system meaning guide with top ERP software, ERP for small business, ERP vendors, cloud-based ERP, and industry-specific ERP solutions.
Escape Velocity Calculator — vₑ = √(2GM/R)
Compute escape velocity for planets, moons, and stars: 3-way solver (v from M & R, R from v & M, M from v & R), verified Earth–Sun presets, light-speed fraction comparison, and orbit-vs-escape explanation.
ESLint Config Generator
High-performance interactive ESLint Flat Config and .eslintrc.json builder with TypeScript, React, Next.js, and 100% SEMrush keyword optimization.
ESLint Config (.eslintrc.js) Generator
Interactive .eslintrc.js config generator, JavaScript file linter, and rule builder supporting React, Node.js, and modern ECMAScript.
Estimated Average Glucose (eAG) Calculator — A1C to mg/dL & mmol/L Converter
Free estimated average glucose (eAG) calculator: convert HbA1c (%) to eAG in mg/dL and mmol/L with the Nathan 2008 (ADAG) equation, plus reference tab
2026 Estimated Tax Calculator — 1040-ES Quarterly Payments & Safe Harbor
Compute 2026 quarterly estimated tax (1040-ES): 90%/110% safe harbor, 15.3% SE tax, due dates & penalty estimate. Education, not tax advice.
Endotracheal Tube (ETT) Size Calculator — Pediatric, Neonatal & Adult
Estimate endotracheal tube (ETT) size by age and weight: Cole formula for children (uncuffed age/4+4, cuffed age/4+3), NRP neonatal weight table, adul
EU to US Shoe Size Converter — Men, Women & Kids Charts | nrtechstudio
Free EU to US shoe size converter for men, women and kids. Two-way conversion bridged by foot length (Mondopoint), plus printable US/EU/UK size charts from ISO/TS 19407 tables. 100% client-side.
EV Charging Cost Calculator — Cost to Charge by Model, Home vs Public, vs Gas
Free EV charging cost calculator with a 65-model vehicle database (Tesla, Ford, Hyundai, Kia, Rivian…): cost per 100 mi/km, home vs public DC fast vs free workplace charging mix, charging-loss math, EV vs gasoline savings, and trip + charge-time estimators. 100% client-side.
eV to MeV Converter | Electronvolt to Megaelectronvolt Calculator
Free ev to mev calculator: convert electronvolts (eV) to megaelectronvolts (MeV) and back. Also converts keV, GeV, joules, photon wavelength and frequency. 1 MeV = 1,000,000 eV.
EV/Sales Ratio Calculator — Enterprise Value to Sales
Free EV/Sales ratio calculator: compute the enterprise value multiple on annual sales, reverse solver (implied EV & implied revenue), 2-company comparator, plus FAQ. 100% client-side.
EVA Foam Thickness & Density Picker for Cosplay Armor | eva-foam-lab
Pick the right EVA foam thickness (2-10mm) and density (38-80 kg/m3) for every cosplay armor piece: helmet, chestplate, bracers, sword, shield. Free sheet estimator, Worbla vs EVA helper, heat-shaping guide.
Evaporation Rate Calculator — Water (Rohwer) & Concrete (ACI 308) | nrtechstudio.com
Free evaporation rate calculator: Rohwer open-water model in mm/day and liters/day, plus ACI 308 concrete evaporation in kg/m²/h with plastic-shrinkage cracking risk warning. Metric/imperial units, formulas, worked example, reference tables.
Exact Value of Trig Functions Calculator — sin, cos, tan in Radical Form
Find exact values of sin, cos, tan, csc, sec, cot as radicals and fractions (√2/2, 1/2, √3) for 48 special angles, with decimals and a unit-circle diagram.
Excel To Json
Excess Electrons Calculator — n = Q/e (2-Way Solver)
Compute excess or deficit electrons from net electric charge (n = Q/e) and vice versa. Exact SI 2019 elementary charge, charge unit conversion, verified worked examples. 100% client-side.
Pregnancy Weight Gain Calculator — IOM Guidelines
Check whether your pregnancy weight gain is on track with the IOM 2009 guidelines: BMI-based targets, weekly rates, 40-week projections, and twin adju
Exclusive Pumping Schedule Calculator — EP Mom Planner | nrtechstudio
Generate an exclusive pumping (EP) schedule, check daily milk output against your baby's estimated needs (150 ml/kg/day), plan weaning, and reference
Exercise Room Size Calculator — 7-Mode Home Gym Space Planner
How much space for a treadmill, bike, rower, or power rack? Free 7-mode calculator plans treadmill zones, cardio spacing, and full home gym rooms.
Exhaust Diameter Calculator — Find the Right Exhaust Pipe Size | nrtechstudio
Free exhaust diameter calculator: find the right exhaust pipe size from engine displacement, max RPM and volumetric efficiency — or from horsepower. Single/dual exhaust, standard pipe sizes, HP vs diameter chart & FAQ.
EXIF Viewer — View Remove Photo Metadata Online (Free, Private)
Free online EXIF viewer: see all camera, exposure & GPS metadata in any photo, check your privacy risk score, and remove EXIF data before sharing. 100% client-side — photos never leave your browser.
Exit Rate Calculator: Compute Page Exit Rate & Compare with Bounce Rate
Free exit rate calculator: compute webpage exit rate (exits ÷ pageviews), compare exit rate vs bounce rate, descriptive internal categorization, and investigation questions when exit rate is high.
Expected Return Calculator — Scenarios, CAPM & Portfolio
Compute investment expected return: probability-weighted scenarios, CAPM model (beta & risk premium), portfolio expected return up to 10 assets, and 2-asset portfolio risk. Educational estimate, not investment advice.
Exponent Solver Calculator — Solve for Exponent or Base with Steps
Free exponent solver calculator: solve for the exponent (a^x = b), solve for the base (x^a = b), solve a^(bx+c) = d, and evaluate fractional & negative exponents — with step-by-step work and answer verification.
Exponential & Logarithmic Equations Calculator Suite
Advanced exponential logarithmic equations calculator, exponential to logarithmic form calculator, log scientific calculator, and recurring decimals as fractions calculator.
Exposure Calculator — EV Triangle Solver, Astro, ND Filter & Shutter Angle
Free exposure calculator: EV triangle solver (lock two settings, solve the third), astrophotography 500 & NPF rules, ND filter long-exposure calculator with bulb timer, shutter-angle converter for video, exposure compensation & HDR bracketing, lux/foot-candle/EV light meter. 100% client-side.
Extract Email Address From Contact Record – Email Extractor & Finder
Email finder by name, email extractor extension, extract email address from contact record, how can i search an email address, email search by email address, how to search an email address, find email address search, find email accounts by name, mac address database, can you lookup email addresses, how to find peoples email addresses, search an email, fb email extractor, download email extractor, email id search by name, get information from email address, find email information, look up email addresses by name, email addresses lookup, best email extractor software, twitter email scraper, email address scanner, dns tool box.
Face Shape Calculator — Find Your Face Shape Free
Free face shape calculator: enter forehead, cheekbone, jawline and face length measurements to find your face shape (oval, round, square, heart, diamo
Factor of Safety (FoS) Calculator — Compute FoS, Allowable Load & Margin of Safety
Free factor of safety calculator: FoS = failure load ÷ working load, two-way solver (FoS from strength/load, or allowable load from target FoS), margin of safety, typical-value table, and metric–imperial unit conversion. 100% client-side.
Fagerström Test for Nicotine Dependence (FTND) Calculator — 6-Question Score 0–10 | nrtechstudio
Free Fagerström Test for Nicotine Dependence (FTND) calculator. Answer 6 questions, get your 0–10 nicotine dependence score, per-item breakdown, inter
Fake Address Generator — Sample Location Gen
Free fake address generator: fictional sample addresses for testing in US, UK & Indonesian formats. Export single-line, JSON or CSV, 100% in your browser.
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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.