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.
GCF of Monomials Calculator
High-performance factoring calculator, greatest common factor of monomials and polynomials solver with step-by-step factorization.
Generator Wattage Calculator — What Size Generator Do I Need?
Generator wattage calculator: enter your appliances' running and starting watts to find the right generator size — honest surge math, headroom guidance, fuel runtime estimator and safety guide.
Georgia Sales Tax Calculator – Multi-State & Local Tax
Georgia sales tax calculator, new york sales tax calculator, ny sales tax calculator, texas state tax calculator, ny state sales tax calculator, california state sales tax calculator, new jersey sales tax calculator, new york city sales tax calculator, how to find tax percentage, how to find sales tax rate, sales tax calculation formula, sales tax calculator app, tax commission calculator.
Golden Ratio Calculator Online
Free golden ratio calculator, golden section ratio calculator, and golden proportion calculator. Calculate golden ratio dimensions, rectangles, typography, and UI design layouts.
Golden Rectangle Calculator — Sides, Area, Perimeter & Diagonal from φ | nrtechstudio
Free golden rectangle calculator: solve short side, long side, area, perimeter and diagonal from any single value (b/a = φ ≈ 1.618034). With nested-squares and golden-spiral diagram. 100% client-side.
Tool - Golden Spiral Dimension Calculator
Interactive Golden Ratio, Golden Spiral, and Golden Rectangle dimension calculator with live visual canvas, Fibonacci layout scale, and typographic sizing.
Grade Curve Calculator: Square Root, Linear, Bell Curve and Flat Add - nrtechstudio
Free grade curve calculator: apply square-root, linear scale, bell-curve z-score, or flat-add curves to test scores. See per-student results and the A-F distribution shift. 100% client-side.
Graduation Calculator by Birthday - High School Class Year and College Graduation
Enter your birthday to find your kindergarten start year, high school graduating class, and college graduation year. Cutoff-date aware, with a redshirt (held-back) option.
Grams to Moles Calculator — Convert g to mol & mol to g (Free Chemistry Tool)
Free grams to moles calculator: convert grams to moles and moles to grams using molar mass. Type any chemical formula (e.g. H2SO4) to auto-compute molar mass from 118 elements, or pick from 48 common compounds. Shows every step.
Graphic Display Calculator Online & Scientific Grapher
Free online graphic display calculator (GDC) and scientific graphing calculator. Plot math functions, calculate stats probability, and solve proportions online.
Graphing Calculator Tool & Statistical Central Tendency Studio
Interactive graphing calculator tool, function plotter, find the mode calculator, mean math calculator, and mean median mode generator.
Newton\
Compute Newton's gravitational force between two masses: 4-way solver (F, M, m, r), verified Earth–Sun presets, results in newton/kN/lbf, comparison vs weight on Earth, and an explanation of force vs weight vs g field.
Gravitational Potential Energy Calculator (U=mgh & U=−GMm/r)
Calculate gravitational potential energy: near-surface U=mgh (U/m/g/h solver) and universal U=−GMm/r (U/M/m/r solver), celestial presets, orbit energy.
Greatest Common Factor & Least Common Multiple Calculator
Interactive GCF and LCM calculator with step-by-step prime factorization, Euclidean algorithm breakdown, polynomial LCM, and multi-number support.
Ground Speed Calculator - Wind Triangle, WCA & Flight Time
Free ground speed calculator for pilots. Enter true airspeed and the wind vector to solve the wind triangle: wind-corrected ground speed, wind correction angle, headwind/tailwind/crosswind components,
Guitar Scale Finder — Reverse Scale Lookup from Notes, Chords Fretboard
Free online guitar scale finder with reverse lookup: enter notes or tap frets to identify the scale, find scales from chord progressions, browse 48 scales with interactive fretboard diagrams and audio playback. 6 & 7 string.
Guitar String Tension Calculator — Per-String & Full Set (lb / kg / N)
Calculate guitar string tension in lb, kg or N. Single-string calculator with gauge picker, scale length and tuning, plus a full 6-string set table with total tension and balance bars. Based on published D'Addario unit weights.
GWh to kWh Conversion – Energy Unit Converter
Free GWh to kWh conversion, joules to units, megawatt to kWh conversion, and convert kWh to GWh calculator.
Hair Diffraction Calculator — Measure Hair Diameter with a Laser
Measure hair diameter from laser diffraction (a·sin θ = mλ). Diameter & fringe-prediction modes, error estimation, experiment diagram, procedure guide.
Hall Coefficient Calculator (R_H) — Hall Effect, Hall Voltage
Hall coefficient calculator: R_H = 1/(n·q) from carrier concentration, carrier type from R_H sign, Hall voltage V_H = R_H·I·B/d. Cu/Ag/Si/Ge presets.
Harmonic Wave Equation Calculator y = A·sin(kx ± ωt + φ) — nrtechstudio.com
Harmonic wave equation calculator: compute displacement y(x,t) = A·sin(kx ± ωt + φ), break the equation into A, k, ω, φ, propagation direction, λ, f, T, v = ω/k, plus an animated wave visualization.
SHA256 Hash Generator & Crypto Calculator
Standalone professional SHA256 hash generator, cryptographic calculator, and secure hash algorithm generator. Hash string sha256, sha-384, sha-512 with HMAC support and live verification.
Hat Size Calculator — Cast-On, Crown Decrease & Brim Planner for Knit Hats
Free hat size calculator for knitters: cast-on stitches from head size and gauge with negative ease, baby-to-adult size chart, round-by-round crown decrease planner, brim/ribbing calculator, and slouchy vs fitted modes. 100% private, works offline.
Headphone Power Calculator — mW, Vrms & Source Checker
How much power do your headphones need? Enter sensitivity and impedance to get required mW, Vrms, V peak and mA for any target SPL, convert dB/mW to dB/V, and check if your dongle, laptop or amp can drive them.
Heart BPM Calculator & Pulse Rate Counter
Interactive heart BPM calculator, live tap tempo pulse counter, target training zones, and beats per minute analyzer.
Heart Rate Zone Calculator — Karvonen, LTHR, Friel, Maffetone (5 Methods)
Free heart rate zone calculator with 5 methods side by side: % of max HR, Karvonen (HRR), LTHR, Joe Friel 7-zone, and Maffetone 180 formula. 3 max-HR estimators (Fox, Tanaka, Nes), running / cycling / swimming presets, method-agreement analysis, and watch-ready zone copy for Garmin, Apple Watch, Coros and Zwift. 100% client-side.
Heat Index Calculator — Apparent Temperature (Rothfusz NWS Formula)
Compute the heat index (apparent temperature) from temperature and relative humidity with the official NWS/NOAA Rothfusz formula. °F/°C input, result + danger categories and safety advice.
Height & Weight Calculator
High-precision Child Adult Height Predictor, Ideal Body Weight Calculator, and Anthropometric Analysis Suite.
Height Converter: Feet and Inches to CM (5'10" Style Input)
Convert height between feet+inches and centimeters, both ways. Type 5'10" directly, see a full conversion chart, BMI healthy weight range, and worked examples.
Heisenberg Uncertainty Principle Calculator (Δx·Δp ≥ ħ/2)
Compute the Heisenberg uncertainty limit: two-way Δx ↔ Δp solver, energy–time mode ΔE·Δt ≥ ħ/2, electron, proton, and macroscopic dust examples, plus ħ vs h explained.
Helmholtz Resonator Calculator — Frequency, Exhaust Drone & Design Solver | nrtechstudio
Free Helmholtz resonator calculator: resonant frequency from volume, neck diameter & length, reverse design solver (volume/length/diameter from target frequency), and exhaust drone tuning from RPM & cylinder count. Metric & imperial, hot exhaust gas temperature, end correction.
Henderson–Hasselbalch Calculator: Buffer pH, Ratio, pKa & Prep — nrtechstudio
Free Henderson–Hasselbalch equation calculator: solve buffer pH, conjugate base/acid ratio, or pKa; prepare lab buffers with exact gram recipes; 34-buffer pKa table at 25 °C, buffer capacity meter, and worked examples.
Heptagon Area Calculator — Regular & Irregular Heptagon | nrtechstudio.com
Free heptagon area calculator. Enter side length, circumradius, or apothem of a regular heptagon to get area, perimeter, diagonals, and angles — plus an irregular heptagon (7-point) mode, live diagram, and worked examples.
Hex Calculator — Hexadecimal Arithmetic (+ − × ÷) with Steps & Bitwise Ops
Free hex calculator: add, subtract, multiply and divide hexadecimal numbers with decimal equivalents, step-by-step working, plus bitwise AND, OR, XOR, NOT and shifts. 100% client-side.
Hex To Bin
Convert hexadecimal numbers to binary.
Hex To Hsl
Convert Hexadecimal colors to HSL format.
Tool - HEX to Hue Saturation Brightness (HSB/HSV) & Color Studio
Ultimate color studio featuring HEX to Hue Saturation Brightness (HSB), HSL, RGB converter, gradient palette builder, image color picker, and hex addition calculator.
Hexadecimal Addition Calculator & Hex Arithmetic Studio
Interactive hexadecimal addition calculator, addition of hexadecimal numbers calculator, and complete hexadecimal arithmetic suite.
Hexadecimal Chart – Binary, ASCII & Hex Math Calculator
Hexadecimal chart, hex translation, hex in string, ascii code to text, hexadecimal encoder, ascii to binary chart, hex code encoder, ascii code decoder, binary coding alphabet, binary number conversion chart, denary to hexadecimal table, binary converter table, adding hexadecimal calculator, char to ascii, binary converter chart, decimal binary hexadecimal chart, hex conversion chart, add hexadecimal numbers, binary hex and decimal table, hexadecimal code for black color, 1e hex to decimal, 0x1f to binary.
Hexadecimal Table Binary – Hex Converter & Reference
Complete hexadecimal to decimal, binary, and ASCII conversion table with hexadecimal calculator, counting, encoding, and reference for hex values.
Hexagon to Binary – Hex, Denary, Octal & Math Calculator
Hexagon to binary, denary to hex converter, denary to hexadecimal, binary to hexadecimal chart, 1010 to hexadecimal, hexadecimal multiplication, hexadecimal sum calculator, convert ip address to hexadecimal, binary to octal calculator, denary to hexadecimal conversion, how to convert octal to binary number, signed integer to decimal converter.
Hiking Water Calculator — How Much Water to Bring Hiking (Free)
Free hiking water calculator: how much water to bring hiking based on your weight, hiking time, temperature, elevation gain and humidity. Refill segment planner, group mode and bottle/bladder planner. 100% client-side, no signup.
Hit Points Calculator 5e — D&D Max HP Calculator
Free D&D 5e hit points calculator. Pick your class hit die, level, and CON modifier — get max HP with average (fixed) or rolled dice, multiclass support, and a level-by-level breakdown.
Hohmann Transfer Calculator — Δv1, Δv2 & Orbit Travel Time
Compute Hohmann orbit transfers: Δv1, Δv2, total Δv, travel time, transfer ellipse semi-major axis, and orbital velocities. Presets from LEO to GEO, Earth to Mars, Earth to Venus.
Hole Volume Calculator
Free hole volume calculator: borehole volume from diameter and depth for drilling and construction, plus concrete-bag, gravel, and spoil estimates.
Homeowners Insurance Calculator — Replacement Cost, Premium Estimator, Hurricane & Condo (HO-6)
Free homeowners insurance calculator: replacement-cost builder, annual premium estimator by state, hurricane/CAT deductible mode, condo HO-6 calculator, Coverage A/B/C/D explainer, and UK/AU/NZ rebuild-cost modes. No sign-up, 100% client-side.
Hoop Stress Calculator - Thin-Walled Pressure Vessel (σ = P·r/t)
Free hoop stress calculator for thin-walled pressure vessels: 4-way solver (stress, pressure, radius, thickness) for σ = P·r/t, plus longitudinal stress, max shear, von Mises and safety factor vs yiel
Horizontal Projectile Motion Calculator — t=√(2h/g), Range & Impact Velocity
Compute horizontal projectile motion: fall time t=√(2h/g), horizontal range R=v₀·t, impact velocity & angle, kinetic energy. Inverse solver + Earth/Moon/Mars gravity presets + SVG trajectory diagram. 100% client-side.
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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.