Free Math & Calculators Tools & Calculators
Browse 710+ free interactive math & calculators calculators, estimators, and utilities. 100% free, private, and runs directly in your browser without signup.
Horse Saddle Size Calculator & Fit Guide — English, Western, Gullet, Cinch | Horse Saddle Lab
Free horse saddle fit suite: English & Western seat size calculator, gullet width guide (narrow/medium/wide/X-wide), cinch length from heart girth, stirrup length by inseam, saddle pad size matcher, plus draft horse and kids modes. Educational estimates — always confirm fit with a professional saddle fitter.
Horsepower Calculator — HP from Torque, 1/4 Mile ET, Trap Speed, Engine Build, EV Boost
Free horsepower calculator lab: HP from torque and RPM, 1/4-mile and 1/8-mile ET, trap speed MPH, engine build (bore, stroke, cylinders, compression, boost), EV kW to HP, plus 0-60 estimator, crank vs wheel HP drivetrain loss, altitude correction, and fuel injector sizing. 100% client-side.
How to Change a Mixed Fraction into a Decimal – Fraction Calculator
Free fraction to decimal calculator with equivalent fractions, mixed number to decimal, long division method, fraction quiz, and step-by-step explanations.
Median Mode and Range Calculator & Statistics Guide
Interactive statistical calculator for median, mode, mean, range, median deviation, and percentile breakdown.
Flesch Reading Ease & Word Readability Calculator
Free online Flesch reading ease calculator and word readability statistics analyzer. Calculate reading level of text and learn how to find readability in word.
How to Find the Diameter of a Circle & Geometry Suite
Interactive circle geometry solver to find diameter, radius, area, circumference in terms of pi, and square footage with dynamic SVG visualizer.
How to Find the Greatest Common Factor
Interactive greatest common factor calculator, Euclidean algorithm solver, prime factorization breakdown, and step-by-step arithmetic guide.
How to Find the Median of 2 Numbers – Mean Median Mode Calculator
Interactive statistics calculator covering mean, median, mode, range, and standard deviation with step-by-step explanations.
Hsl To Hex
Convert HSL colors to Hexadecimal format.
HSV to Hex Converter
Enterprise-grade interactive HSV to Hex color converter, Hex code to HSV reverse calculator, and color space harmony suite with 100% SEMrush keyword optimization.
Hubble’s Law Calculator (v = H₀ × d) — Free, Client-Side
Hubble’s law calculator: compute recession velocity v, distance d, or the Hubble constant H₀. Planck 2018 & SH0ES presets, Hubble time tᴴ = 1/H₀, and redshift approximation.
Hydraulic Jump Calculator — Conjugate Depth via Froude
Free hydraulic jump calculator: compute conjugate depth y₂ from upstream Froude number Fr₁, energy loss ΔE, efficiency, jump length, and jump-type classification (undular–strong).
Hydraulic Radius Calculator — R = A/P (6 Channel Shapes + Depth Solver)
Free hydraulic radius calculator: compute R = A/P for rectangular, trapezoidal, triangular, full circular, partially filled circular, and semicircular channels, with depth-from-R solver and hydraulic depth A/T.
Hydrostatic Pressure Calculator (P = ρgh) - Solve, Convert Units, Force on Surface
Free hydrostatic pressure calculator: solve P = ρgh for pressure, density, gravity, or depth. Fluid presets (water, seawater, oil, mercury, glycerin), 7 pressure units, and force on a submerged surfac
Hypergeometric Distribution Calculator — P(X=k), CDF, Mean, Variance
Free hypergeometric distribution calculator: P(X=k), P(X≤k), P(X≥k), mean and variance for sampling without replacement. Card, lottery and QC sampling examples, PMF chart and table.
Hypotenuse Calculator — Pythagorean Theorem Solver
Free hypotenuse calculator: solve any side of a right triangle with the Pythagorean theorem. Three modes (legs to hypotenuse, hypotenuse to leg), Pythagorean triple checker, length unit converter, and a live triangle diagram.
Hz to Seconds & Period Calculator
Interactive frequency to period converter, calculating hz to seconds, angular frequency in rad/s, and wave periods.
Ideal Gas Law Calculator (PV = nRT) - Solve P, V, n, T + Moles↔Mass + Density
Free ideal gas law calculator: solve PV=nRT for pressure, volume, moles or temperature with full unit mixing, convert moles↔mass via molar mass, compute ideal-gas density ρ=PM/RT, and see R in every u
Ideal Rocket Equation Calculator (Tsiolkovsky)
Solve the Tsiolkovsky ideal rocket equation in every direction: delta-v, specific impulse, mass ratio, initial/final mass and propellant mass. Multi-stage rockets, propellant presets and mission delta
Img Resizer Calc
Calculate proportional dimensions for resizing images.
Impact Energy Calculator
Free impact energy calculator: kinetic energy (E = 1/2 m v^2), drop impact (E = m g h), inverse solvers for velocity and mass, with joules, kJ, ft-lbf and calorie output plus equivalent drop height.
Inductive Reactance Calculator - XL = 2πfL Solver
Free inductive reactance calculator: compute XL = 2πfL, 3-variable solver (XL/f/L), XL vs frequency table, ideal impedance + +90° phase angle. 100% offline.
Inductor Energy Calculator - E = 1/2 L I^2
Free inductor energy calculator: solve E = ½LI² in all three directions (energy, inductance, current) with unit conversion and a capacitor-energy comparison readout.
INI to JSON Converter
Enterprise-grade INI to JSON Converter, Online INI Parser, and Configuration Transformer with 100% SEMrush keyword optimization.
Injury Settlement Calculator — Personal Injury, Car Accident & Workers' Comp Lab
Free injury settlement lab: personal injury multiplier estimator, car accident settlement calculator with diminished value, interactive multi-state workers' comp body-part payout chart, state comparison view, and net-after-fees take-home calculator. 100% client-side, no signup.
Insertion Loss Calculator — Calculate IL from Power & Voltage (dB)
Free insertion loss calculator: IL = 10·log10(Pin/Pout) for power and 20·log10(Vin/Vout) for voltage. 3-way solver, W/mW/dBm/V/mV units, dB-to-linear-ratio conversion, and multi-stage cascade.
Instrument Size Lab — Guitar, Violin, Viola, Cello & Ukulele Size Finder
Find the right instrument size: guitar size by height & age, violin fractional size by arm length, viola, cello, and the right ukulele (soprano vs concert vs tenor vs baritone). Free, private, no sign-up.
Interest Paid Monthly Calculator & APR Solver
Interactive interest paid monthly calculator, calculate monthly interest from APR, and interest over time calculator amortization.
Modular Inverse Calculator — Extended Euclidean Algorithm with Steps
Free modular inverse calculator: compute a⁻¹ mod m with the extended Euclidean algorithm, full step table, coprimality check, and a·x ≡ 1 verification.
Inverse Square Law Calculator
Free inverse square law calculator: solve I1/I2 = (d2/d1)^2 for intensity or distance. Presets for light (lux), sound (dB SPL, 20*log10), gravity, and radiation, plus a doubling-distance table. 100% c
IP to Hex Converter — IPv4 to Hexadecimal
Convert IPv4 to hex free: dotted hex (C0.A8.01.01), 0xC0A80101, 32-bit decimal and binary, per-octet math steps, plus batch mode.
Ipv4 To Binary
Convert an IP address to its binary representation.
Is It a Right Triangle? — Right Triangle Checker Calculator
Enter any 3 side lengths to check whether they form a right triangle. Verifies a²+b²=c² with float tolerance, classifies acute / right / obtuse, and computes angles, area (Heron) and perimeter with a live diagram.
Isosceles Triangle Calculator — Side, Angle, Area & Perimeter Solver | nrtechstudio.com
Free isosceles triangle calculator and solver. Enter two equal sides + base, side + apex angle, base + base angle, or height + base to get all sides, both angles, height, area, and perimeter — with a live diagram and worked examples.
Joule Heating Calculator - P = I2R Power, Energy and Temperature Rise
Free Joule heating calculator: solve P = I2R = V2/R = VI for power, current, voltage or resistance, compute heating energy over time, and estimate temperature rise. 100% client-side.
Joule to Kcal & Energy Units Converter
Free online Joule to Kcal calculator and energy conversion tool. Convert joules to calories, cal to joules, kJ to kcal, and explore step-by-step energy conversion formulas.
JSON to INI Converter
High-performance interactive JSON to INI Converter, INI to JSON parser, and configuration file transformer with 100% SEMrush keyword optimization.
Jwt Decoder
Decode JSON Web Tokens instantly.
JWT – Secret Key Generator, Token Decoder & SHA-256 Hasher
Decode hex, what is sha256, access token decode, jwt secret key generator, sha256 hasher, jwt secret generator, sha1 hash decrypter, sha 256 decrypt, algorithm sha 256, jwt在线解密, decrypting sha256, sha1 hash decoder, how does sha 256 work, decrypt sha1, json extractor, sha256 encrypt, sha256 encoder, sha256 calc, is sha256 secure, sha hashing algorithm, sha256 code, decode rsa, oauth token decode, sha256 hash decoder, sha 256 hash decoder, python decode jwt, json web token node, go url encode, how jwt token works, sha256 hash decrypt.
Kayak Size Calculator — Kayak Size + Paddle Length + Fit Planner
Free kayak size calculator: find the right kayak length and width for your height, weight and paddling style (recreational, touring, sea, whitewater, fishing, sit-on-top, tandem, inflatable). Includes kayak paddle length solver, weight capacity check and cockpit size chart. 100% client-side.
Kepler Third Law Calculator: Orbital Period, Radius & GM Solver
Free Kepler third law calculator: T² = 4π²a³/μ. Solve for orbital period T, semi-major axis a, or gravitational parameter μ, with preset μ for Sun, Earth, Moon and Mars plus mean orbital velocity v =
KG to Pounds Converter
The ultimate Kilograms to Pounds Converter, Lbs to KG Calculator, and Weight Unit Conversion Suite with 100% SEMrush keyword optimization.
Kinematic Viscosity of Air Calculator | Sutherland Model
Free kinematic viscosity of air calculator. Compute nu = mu/rho from temperature (Sutherland formula) and pressure (ideal gas), with unit conversions and a reference table.
kJ to Cal Calculator & Kilojoules to Kilocalories Converter
Interactive kJ to cal calculator, convert kJ to kcal, conversion kj en kcal, and kilojoules to kilocalories food nutrition tool.
Knit Crochet Lab — Gauge Calculator, Needle/Hook Converter Yarn Yardage
Free knit & crochet lab: knitting gauge calculator (swatch to cast-on stitches), pattern gauge adjustment, interactive US/UK/mm knitting needle & crochet hook size converter, yarn yardage estimator from Craft Yarn Council ranges, and a beginner project recommender. 100% private, works offline.
Knit Increase/Decrease Calculator — Increase & Decrease Evenly Across a Row
Free knit increase/decrease calculator: space increases or decreases evenly across a row or round, exclude edge stitches, get written row-by-row instructions. Works for kfb, M1, k2tog, ssk. 100% private, runs in your browser.
Knudsen Number Calculator
Free Knudsen number calculator: compute Kn = λ/L from the mean free path and characteristic length, or from kinetic theory (λ = kB·T/(√2·π·d²·P)). Classifies continuum, slip-flow, transition and free-
Large Exponent Calculator — Big Power, Modular Exponentiation & Last Digits | nrtechstudio
Compute huge powers exactly with BigInt (digit count, scientific notation), run fast modular exponentiation a^b mod m with step-by-step square-and-multiply, and find last digits of giant powers. 100%
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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.