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.
Vanity Size Calculator — Single & Double Sink Widths, Height & Depth
Vanity size calculator: single and double sink widths, standard height and depth, IRC clearance checks, and mirror pairing — inches and centimeters, f
Vapor Pressure Deficit (VPD) Calculator — kPa, Leaf VPD & Grow Chart
Free vapor pressure deficit calculator: air & leaf VPD in kPa from temperature and humidity (Tetens equation), growth-stage zones (seedling, veg, flower), dew point, target humidity, and a full VPD ch
VAT Number Validator
Free EU VAT number format validator with real check-digit math (ISO 7064, Luhn, MOD 97, elfproef) for 31 countries. 100% client-side.
VBAC Risk Score Calculator (Grobman 2007 & 2021) — Probability of Successful Vaginal Birth After Cesarean — NR Tech Studio
VBAC success probability calculator using the Grobman 2007 model and the 2021 race-free update (SMFM): age, BMI, vaginal/VBAC birth history, recurring cesarean indication, chronic hypertension. With per-factor explanations, risk categories, VBAC vs repeat cesarean comparison, contraindication checklist, and FAQ. Educational tool — not medical advice.
vCard Parser — Parse vCard to JSON Online
Free online vCard parser: paste vCard text or upload a .vcf file to parse it into structured JSON. vCard 3.0 & 4.0, multi-contact, 100% client-side.
Vector Norm Calculator — L1, L2, L∞ Norms, Unit Vector, Distance & Angle | NR Tech Studio
Free vector norm calculator: compute L1 (Manhattan), L2 (Euclidean), L∞ (max) norms, unit vector, vector distance, dot product, and angle between vectors. 100% client-side, no server.
Vegan Carbon Footprint Calculator — Diet CO2e vs Omnivore, Vegetarian, Pescatarian
Free vegan carbon footprint calculator: enter your weekly plant-food consumption and see your diet
Vegetable Yield Calculator — Harvest Estimate per Plant & Bed Size
Estimate your vegetable garden harvest: yield-per-plant ranges for 22 common vegetables, plants-from-bed-size, totals in lb and kg, plus a succession planting guide.
Relativistic Velocity Addition Calculator - Einstein Formula | nrtechstudio
Free relativistic velocity addition calculator: Einstein's 1D and 2D formulas u = (v+u')/(1+vu'/c^2), inverse solver, and rapidity phi = artanh(u/c).
Velocity Calculator — v, Δx, t, Average & Unit Conversion
Generic velocity calculator: solve v from Δx and Δt, distance from v and t, time from Δx and v, multi-segment average velocity, and m/s, km/h, mph, ft/s, knot, fraction-of-c conversion. Pure constant-velocity motion.
Vet Cost Estimator — Dog & Cat Vet Bill Calculator (2026) | nrtechstudio.com
Free vet cost estimator: estimate routine, emergency, surgery & chronic care costs for dogs and cats, compare pet insurance vs self-pay, and project lifetime vet bills. US 2026 estimates.
Video Bandwidth Calculator & Streaming Bitrate Studio
Interactive video bandwidth calculator, streaming bitrate calculator, and streaming video bandwidth calculator for broadcasters and creators.
Video Bitrate Calculator — YouTube, Twitch & Facebook Bitrate Settings
Free video bitrate calculator: optimal H.264/H.265/AV1 bitrates for YouTube, Twitch & Facebook (240p–8K, 24–120 fps), upload headroom checks and per-hour file sizes.
Video & WhatsApp Link Generator
Free online video link generator, WhatsApp short link maker, and hyperlink tool. Convert URL to hyperlink, create web links, and generate embed codes.
Video Schema Markup Generator
Interactive Schema.org VideoObject JSON-LD generator with ISO 8601 duration calculator and Google Video SERP preview.
Video File Size Calculator & Bitrate Storage Calculator
Standalone video file size calculator, video size calculator, video bit rate calculator, streaming video bitrate calculator, and storage calculator for video. Estimate video size by bitrate and duration with zero AI slop.
Viewport Calculator
Enterprise-grade responsive viewport calculator, CSS clamp() fluid typography generator, and screen resolution analyzer with 100% SEMrush keyword optimization.
Villain Name Generator – Stage Name & Dark Persona Studio
Villain name generator, stage name generator, dark name generator, create a stage name generator, 5 letter name generator.
Virtual Temperature Calculator (Tv) — Meteorology
Meteorology virtual temperature calculator: Tv = T(1 + 0.61q). Compute Tv from relative humidity, dew point, specific humidity, or mixing ratio — plus moist vs dry air density comparison. 100% client-side.
Predicted Vital Capacity (VC) Calculator — Baldwin, ECSC & NHANES III
Calculate predicted vital capacity (VC) from height, age, and sex using three verified reference equations: Baldwin 1948, ECSC 1993, and NHANES III 1999. Includes % predicted, LLN, interpretation, reference tables, and a trend logger.
VLDL & Friedewald Lipid Panel Calculator — VLDL, LDL, Non-HDL + Ratios
VLDL & Friedewald lipid panel calculator: compute VLDL, LDL (Friedewald), non-HDL, and TG/HDL, total/HDL, LDL/HDL ratios from total cholesterol, HDL, and triglycerides. mg/dL↔mmol/L toggle, TG≥400 validity flag, NCEP ATP III target table, and FAQ.
VO2 Max Calculator — 5 Test Methods Compared (Cooper, Rockport, VDOT)
Free VO2 max calculator with 5 methods side-by-side: Cooper 12-min run test, 1.5-mile run, Rockport 1-mile walk test, Uth heart-rate ratio & Jack Daniels VDOT. ACSM fitness classification by age and gender. 100% client-side, no signup.
Vocabulary Quiz Maker — Free Printable Matching, Multiple Choice & Fill-in-the-Blank Quiz Generator
Free vocabulary quiz maker for teachers: paste a word list and instantly generate printable matching, multiple choice (with smart distractors) and fill-in-the-blank quizzes with automatic answer keys. No sign-up, 100% in your browser.
Voltage Calculator — Ohm's Law, Voltage Divider, LED Resistor & Wire Drop
Free voltage calculator: solve Ohm's law for any 2 of V, I, R, P (6 combinations), design voltage dividers (forward, reverse, loaded), size LED resistors with E12 values, and estimate DC wire voltage drop.
Voltage Converter — Volts, mV, kV, dBmV, Divider & Drop Calculator | nrtechstudio
Free voltage & electric potential converter: V, mV, µV, kV, MV, statvolt, abvolt — plus voltage divider solver, Ohm
Voltage Drop Calculator — Wire & Cable (NEC 3% / 5%)
Free wire voltage drop calculator: Vd = 2·K·I·L/cmil for DC & single-phase, √3·K·I·L/cmil for 3-phase. NEC 3%/5% verdicts, AWG 8–22 table, max-length and minimum-wire-size reverse solvers.
Voltage Regulation Calculator (%VR) — No-Load vs Full-Load | nrtechstudio
Free voltage regulation calculator: compute %VR = (V_no-load − V_full-load)/V_full-load × 100, solve the inverse (find V_full-load or V_no-load from %
Volts to eV Converter — Charge-State Calculator
Convert volts to electronvolts (eV) with charge state z: E(eV) = V × z. Reverse eV to volts, plus joules. For electrons, He²⁺, Al¹³⁺ and heavy ions.
Volts to Joules Calculator | Electrical Energy from Voltage
Convert volts to joules: E = V x I x t (power times time), E = V x Q for batteries (mAh to joules), and capacitor energy 1/2 CV squared. Free calculator with kJ and Wh results.
Volts to Ohms Calculator — Ohm's Law Lab (V=IR Solver, Divider, Power Rating)
Free volts to ohms calculator: solve R from V and I, full Ohm
Volume Calculator Cylinder & Circle Suite
High-precision Cylinder Volume, Circle Area, Circumference, Diameter, and Mass Density Converter.
Volume Converter - Liters, Gallons, mL, Cups, Cubic Feet & More
Free volume converter: liters to gallons, mL, cups, fl oz, cubic feet and more. Live two-way results, batch mode, exact US/UK gallon factors. 100% client-side.
Volume Formula Cylinder Calculator & Diameter Studio
Interactive volume formula cylinder calculator and cylinder diameter calculator with 3D visualization and liquid volume conversions.
Volume of a Triangular Prism Calculator — Free Online
Free volume of a triangular prism calculator: enter the triangle base (base × height, or 3 sides via Heron's formula) plus the prism length to get volume, surface area, a labeled diagram, and step-by-step working.
Sphere Volume & Circumference Calculator
Free volume sphere calculation tool, radius of sphere calculator, and circumference of a sphere calculator with 3D interactive preview.
Volume to Density Calculator — 3-Way ρ/m/V Solver, Material Table & Mixtures
Free volume to density calculator: 3-way solver for density, mass, and volume (ρ = m/V), volume from box/cylinder/sphere dimensions, 30-material density table, two-material mixture density, and specific gravity. 100% in-browser.
VSWR (Voltage Standing Wave Ratio) Calculator — nrtechstudio.com
Free VSWR calculator: compute voltage standing wave ratio from reflection coefficient, forward/reflected power, return loss, reflected power %, mismatch loss, and impedance. Complete with reference tables & formulas.
Pregnancy VTE Risk Calculator (RCOG 37a) — Antenatal & Postnatal
Venous thromboembolism (VTE) risk assessment in pregnancy per RCOG Green-top Guideline No. 37a: antenatal & postnatal risk factor checklist, automatic stratification, weight-based LMWH dose table, and FAQ. Educational tool, not medical advice.
WebVTT to SRT Converter & Subtitle Tool
Standalone professional VTT to SRT converter, online SRT to VTT converter, and WebVTT to SubRip subtitle converter. Convert VTT to TXT, convert VTT to Word, and vtt转srt with zero AI slop.
W2 vs 1099 Calculator — True Hourly Rate Comparison (2026)
Compare a W-2 salary to a 1099 contractor rate honestly: true hourly rates, self-employment tax (15.3% = 12.4% + 2.9%), benefits, PTO, billable hours, and the break-even 1099 rate. Free, private, no signup.
WhatsApp Link Generator Online
Free WhatsApp link generator, WhatsApp link maker, and WhatsApp chat link generator. Create click to chat WhatsApp link (wa.me), link api whatsapp, and QR code.
Wage Garnishment Calculator
Free 2026 wage garnishment calculator: creditor, student loan, child support and IRS levy limits in all 50 states, with federal and state rules.
Wage Growth Calculator
High-performance Wage Growth, Compound Interest, Investment & Real Inflation Calculator.
Wage to Salary Calculator & Hourly Converter
Interactive wage to salary calculator, monthly salary to hourly pay calculator, overtime wages, and pay period breakdown.
Wainscoting Layout Calculator — Beadboard, Raised Panel, Picture Frame & Chair Rail | nrtechstudio.com
Free wainscoting layout calculator for 4 styles — beadboard paneling, raised-panel, picture-frame molding, and chair rail + baseboard. Enter wall length, get equalized panel widths, stile positions, a to-scale diagram, and a material shopping list. 100% client-side.
Waist-Hip Ratio (WHR) Calculator — WHO Risk Classification
Free WHR calculator: compute your waist-hip ratio (cm/in), see the WHO risk classification for men and women, cutoff tables, correct measuring guide, and WHR vs BMI comparison. 100% in your browser.
Walkway Size Calculator: Width, Pavers, Concrete, Gravel & Cost | nrtechstudio.com
Walkway size calculator: width by use case, paver count, concrete volume, gravel path, stepping stones, slope/steps, and cost. 7 free modes.
Wallpaper Calculator — How Many Rolls Do You Need? | nrtechstudio.com
Free wallpaper calculator with pattern-repeat math: strips per roll, straight vs half-drop match, window/door deduction, wall diagram, single vs double roll cost. Metric + imperial.
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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.