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.
AC Size Calculator — What Size Air Conditioner for Your Room? (BTU, Tons, kW, PK)
Free AC size calculator: enter room dimensions and get the right air conditioner size in BTU/hr, tons, kW and PK. Adjusts for climate zone, insulation, sun exposure, windows, ceiling height, occupants and kitchen heat.
Air Density Calculator — CIPM-2007 (kg/m³, Density Altitude) | nrtechstudio.com
Free air density calculator using the CIPM-2007 moist-air equation. Enter temperature, pressure & humidity → get density in kg/m³, g/m³, lb/ft³, density altitude & pressure altitude. 100% in-browser, no sign-up.
Air Force PT Calculator — USAF PFRA Score Calculator (2026 Standards)
Free USAF Physical Fitness Readiness Assessment (PFRA) score calculator. Enter push-ups, core, 2-mile run or HAMR, and waist-to-height ratio to estimate your score out of 100 by age group and gender. Unofficial training aid.
Air Pressure at Altitude Calculator (ISA Barometric Formula) — nrtechstudio.com
Free air pressure at altitude calculator using the layered ISA barometric formula. Enter altitude in m/ft (optional temperature) to get pressure in hPa, Pa, psi, inHg, mmHg, % of sea level, ISA temperature, boiling point of water, a 0–20,000 m standard atmosphere table, and reverse pressure→altitude mode. 100% client-side.
Air Purifier Room Size Calculator (CADR) — AHAM & EPA Sizing | nrtechstudio.com
What size air purifier do you need? Enter room size for the minimum smoke CADR via the AHAM 2/3 rule and EPA table, with ACH breakdown.
Airport Code Finder — Search 9,051 IATA/ICAO Codes by City, Name or Code
Free online airport code finder: instantly search 9,051 airports by IATA code, ICAO code, name, city or country. Get coordinates, elevation, distance between airports, and airports near you. 100% client-side, no signup.
Albumin/Globulin Ratio Calculator — A/G Ratio + Inverse Solver | nrtechstudio.com
Free A/G ratio calculator: albumin/globulin ratio from total protein and albumin, unit conversion g/dL to g/L, inverse solver for albumin or globulin
Alcohol Dilution Calculator (C1V1=C2V2) — ABV & Proof | nrtechstudio.com
Free alcohol dilution calculator: C1V1=C2V2 for spirits and homebrew. Enter start ABV, target ABV and volume — get water to add, final volume, ABV/Proof toggle and a what-if dilution table.
Alcohol Units Calculator — UK Units + Weekly Tracker (Free) | nrtechstudio
Free UK alcohol units calculator: units = volume (ml) × ABV ÷ 1000. UK drink presets (pint, wine, spirits), a 7-day tracker vs the 14-unit weekly guid
Aldrete Score Calculator — Post-Anesthesia Recovery & PACU Discharge Score | nrtechstudio.com
Free Aldrete score calculator: interactive 5-criterion postanesthetic recovery scoring (original colour and modified SpO2 versions), blood-pressure de
Aleve Dosage Scheduler & 24-Hour Tablet Counter (Naproxen 220 mg)
Educational Aleve (naproxen sodium 220 mg) dose scheduler: track tablets in 24 hours, see your earliest next dose per the OTC label, and compare Aleve
Allele Frequency Calculator (Hardy-Weinberg)
Free allele frequency calculator: enter genotype counts (AA, Aa, aa) to get p and q, expected Hardy-Weinberg genotype frequencies (p^2, 2pq, q^2), and a chi-square goodness-of-fit test (df=1) with p-v
Alphabetical Order Tool & List Sorter
Interactive online alphabetizer tool to alphabetize names, sort word lists, and generate MLA reference lists in alphabetical order.
Altitude Temperature Calculator — ISA Lapse Rate & 0–20 km Profile
Free altitude temperature calculator: ISA lapse-rate T = 15 − 6.5×h for 0–11 km, isothermal −56.5°C stratosphere to 20 km. Convert altitude→temperature, temperature→altitude, and plot the 0–20 km prof
Aluminum Weight Calculator — Sheet, Plate, Bar, Tube, Angle & Channel
Free aluminum weight calculator: compute weight from dimensions for sheet, plate, round bar, square bar, tube, angle, channel and hex bar. Alloys 6061, 5052, 7075, 1100. Metric + imperial (kg, lb).
American Flag Size & Proportions Calculator — Official US Flag Dimensions
Free American flag size and proportions calculator. Enter any one dimension — hoist, fly, union, stripe height, or star diameter — and get every official US flag measurement per Executive Order 10834, with a to-scale SVG preview and standard sizes chart.
Equal Principal Amortization Calculator — Fixed Principal Payment Schedule
Calculate an equal-principal (constant principal) amortization schedule: a fixed principal portion each period, declining payments, total interest, and a side-by-side comparison with a standard equal-payment (annuity) loan. Free, private, runs in your browser.
Interest-Only Loan Amortization Calculator
Interactive financial calculator generating complete amortization tables for interest-only loans, personal loans, and deferred payment loans.
Amoxicillin Pediatric Dosage Calculator (Educational Estimator) — nrtechstudio.com
Educational pediatric amoxicillin dose estimator by weight: mg per dose and mL per dose for common suspensions (125/5, 200/5, 250/5, 400/5), standard vs high-dose regimens. Not medical advice — final dosing by a doctor or pharmacist.
Amps to kW Calculator — DC, Single-Phase & 3-Phase Converter
Free amps to kW calculator: convert amps to kilowatts for DC, single-phase and three-phase (line-to-line / line-to-neutral) with power factor. Also kW to amps, amps to watts, amps to kVA, and a breaker-size chart. 100% client-side.
Amps to Milliamps (mA) Converter — A ↔ mA ↔ µA ↔ nA | nrtechstudio
Free amps to milliamps converter: convert A ↔ mA ↔ µA ↔ nA ↔ kA with scientific notation, plus battery runtime, car parasitic-drain, shunt resistor, and fuse-size calculators. 100% client-side, no signup.
Amps to Ohms Calculator — Convert Amps to Resistance (DC, AC, 3-Phase)
Free amps to ohms calculator: convert amps to resistance for DC, AC single-phase and 3-phase circuits, reverse ohms to amps, Ohm
Anagram Checker - Check If Two Words Are Anagrams + Solver
Free online anagram checker: test whether two words or phrases are anagrams (ignores case, spaces, punctuation), with sorted-letter comparison visuals and an anagram solver for short words.
ANC Calculator Without Bands — Absolute Neutrophil Count
Free ANC calculator without bands: compute Absolute Neutrophil Count from WBC and segmented neutrophils (segs), with category, gauge, formula breakdown, optional with-bands comparison, and FAQ. Educational tool.
Anchoring Lab — Anchor Size Selector, Scope & Swing Circle Calculator
Free anchoring calculator: anchor size selector comparing 5 manufacturer charts (Danforth, Fortress, Lewmar, Rocna, Mantus), anchor scope calculator, swing circle calculator and chain vs rope rode guide. 100% client-side.
Angle Converter - Degrees, Radians, Gradians, Turns & More
Free angle converter: convert degrees, radians, gradians, turns, arcminutes, arcseconds and milliradians live, with exact pi fractions, batch mode and DMS readout.
Angle of Elevation & Depression Calculator: Height, Distance & Triangle Angles – Developer Tools
Free angle of elevation and depression calculator: find the angle from height and horizontal distance, or reverse it - find height from angle and distance, find distance from angle and height. Results in degrees, radians, and degrees-minutes-seconds, with a triangle diagram.
Angle of Refraction Calculator — Snell's Law, Critical Angle & TIR
Free angle of refraction calculator: apply Snell's law (n1·sinθ1 = n2·sinθ2) to find the refracted angle, solve for an unknown refractive index, and compute the critical angle with total internal refl
Angle of Twist Calculator — Torsion Formula φ = TL/(GJ)
Free angle of twist calculator for torsion: φ = T×L/(G×J). Solve twist angle, torque, length, shear modulus, or polar moment. Solid & hollow shafts, shear modulus table, shear stress τ = T×r/J.
Angular Acceleration Calculator — α = Δω/Δt
Free angular acceleration calculator: compute α from angular velocity change & time, from torque & moment of inertia (α = τ/I), missing-variable solver, and rad/s², rpm/s, deg/s² conversion.
Angular Displacement Calculator - theta, delta theta, rad/degree/revolution conversion
Angular displacement calculator: find missing variable thetaf, theta0, omega, t, or delta theta (Δθ = θf − θi, θ = θ₀ + ωt), radian degree revolution conversion, and arc length s = rθ.
Angular Velocity Calculator — ω = Δθ/Δt, ω = 2πf, v = ωr Solver | nrtechstudio
Free angular velocity calculator: solve for ω, Δθ, Δt, frequency, or radius with ω = Δθ/Δt, ω = 2πf, and v = ωr. Convert rad/s ↔ rpm ↔ deg/s ↔ Hz. 100% client-side.
Animal Mortality Rate Calculator — Per-Period, Annualized & Life Table (Free)
Free animal mortality rate calculator for livestock, poultry and lab animals. Enter starting population and deaths to get mortality rate, survival rate, annualized mortality, a simple life table and g
Anion Gap Calculator — AG, Albumin-Corrected, Delta Gap & Osmolar Gap
Free anion gap calculator: AG = Na − (Cl + HCO₃), albumin-corrected anion gap, delta gap & delta ratio for mixed acid–base disorders, plus osmolar gap
Annealing Temperature Calculator for PCR Primers | nrtechstudio.com
Free PCR annealing temperature calculator: enter your primer sequence and get Tm by 4 methods (Wallace, GC-content, salt-adjusted, nearest-neighbor) plus the recommended annealing temperature (Tm − 3–5°C). 100% client-side.
Annualized Rate of Return Calculator — CAGR Compared
Free annualized rate of return calculator: CAGR from start/end value and years or exact dates. Compare CAGR vs average annual return. Runs 100% in your browser.
Annuity Calculator — Future Value, Present Value & Payout
Free annuity calculator: future value and present value of ordinary annuity & annuity due, payment solver, and lump-sum annuity payout calculator with schedules. 100% client-side.
Antenna Lab: Dipole, J-Pole, Mag Loop & Yagi Calculator
Free wire antenna design suite: dipole & inverted-V calculator (468/f), quarter-wave vertical + radial planner, random wire & end-fed half-wave (EFHW), J-pole & Super J-pole, magnetic loop tuning capacitor calculator, multi-element Yagi designer, length converter and wire gauge reference. Metric + imperial. 100% client-side.
AP Chemistry Score Calculator — Estimate Your AP Chem Score (2025)
Free AP Chemistry score calculator: enter your multiple-choice correct answers and FRQ points to estimate your composite score (of 110) and AP score 1-5, using the official College Board weighting. 100% client-side.
AP Lang Score Calculator 2026 — Estimate Your 1–5 AP English Language Score
Free AP English Language and Composition score calculator (2026 exam format): enter 45 multiple-choice correct + three 0-6 essay scores to estimate your 1-5 AP score with the official 1.2272 / 3.0556 composite formula.
APACHE II Score Calculator — ICU Severity Score + Mortality Estimate
Free APACHE II Score calculator: compute ICU disease severity score from 12 physiologic variables + age + chronic health (total 0–71) with per-variable breakdown, gauge, and Knaus mortality estimate table as context. Educational tool, not a substitute for clinical judgment.
Apache Linter — Check .htaccess & httpd.conf Syntax Online
Free online Apache .htaccess and httpd.conf linter. Heuristic client-side checker: directive typos, RewriteRule flag validation, block balance, wrong-context directives, and risky settings. No uploads.
Aperture Area Calculator — Lens Opening Size, f-number to mm²
Free aperture area calculator: focal length ÷ f-number → aperture diameter and area in mm², cm², in². Missing-value solver + relative light gathering vs f/1.0.
APFT Score Calculator — Legacy Army Physical Fitness Test (300 pts)
Free APFT score calculator: enter push-ups, sit-ups and 2-mile run plus age and gender to estimate your legacy Army Physical Fitness Test score (0–300) with the 60-point pass gate per event. Simplified from published FM 7-22 standards.
Apgar Score Calculator — Newborn 1-Minute & 5-Minute Assessment | nrtechstudio.com
Free Apgar score calculator: score a newborn's Appearance, Pulse, Grimace, Activity, and Respiration (0-2 each) at 1, 5, and 10 minutes. Total 0-10 wi
API Gravity Calculator - SG to Degrees API, Classification and Blend
Free API gravity calculator: convert specific gravity to degrees API and back, classify crude as light, medium, heavy or extra-heavy, convert to kg/m3, lb/gal and barrels per metric ton, and blend two
API Tester — Free Online REST Client
Test HTTP API endpoints in your browser: GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS with query params builder, headers, JSON body validation, response viewer and request history.
App Programming Company – Mobile App Development Agency Hub
Landing page hub showcasing NRStudio's mobile app development tools and resources, targeting app programming company and mobile application development agency keywords.
🔍 No tools matched your search
Try a different keyword like "calculator", "planner", "converter" - or pick a category above.
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.