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.
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.
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.
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.
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.
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.
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.
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.
What Is My Relative to Me? — Family Relationship Finder
Type 'my cousin's daughter' or 'my mom's cousin' and get the exact relationship name — first cousin once removed, second cousin, great-aunt — with a plain-English explanation, family tree diagram, shared DNA %, and an interactive cousin chart. Free, private, no sign-up.
Tool - Feet and Inches to Cm Converter
Universal metric conversion calculator for feet and inches to cm, meters to feet, height converter, and area conversions.
Fence Calculator — Posts, Pickets, Concrete & Cost Estimator
Free fence material calculator: wood privacy, picket, chain link, vinyl & metal fences. Multi-run L-shape layout, gate planner, farm/acre mode, electric fence mode, concrete per post & cost estimator. 100% private — runs in your browser.
Fermi Level Calculator — Free Electron Gas Fermi Energy
Interactive Fermi level calculator: E_F from electron density n (2-way E_F↔n solver), Fermi temperature T_F, Fermi velocity v_F, Fermi momentum, plus verified metal presets (Cu, Al, Ag, Au, Na).
Fibonacci Generator — Sequence, Nth Term & Golden Ratio
Free online Fibonacci sequence generator with exact BigInt precision: generate N terms, compute the nth term with fast doubling, golden-ratio convergence, sums, parity stats, and Pisano periods. 100% client-side.
Tool - Final Calculator & Final Exam Calculator
High-precision final grade calculator and final exam score calculator. Computes the exact score needed on your final exam to achieve your target class grade.
Financial Calculator
High-performance, multi-mode financial calculator & loan calculator software for compound interest, TVM, loan amortization, ROI, and retirement planning.
Find the Area of a Shape – Polygon & Irregular Shape Calculator
Find the area of a shape, online square feet calculator, polygon area calculator, land area calculator, equations for area of shapes, area and perimeter calculator, formula to find area, area of irregular figures calculator, calculate image, area calculator odd shape, rectangular surface area calculator, maps area calculator, area of a figure calculator, rectangular area calculation, sq area calculator, how to find the total area of a shape, area calculator with feet and inches, total area calculator, area square calculator, how to figure out the area of a shape, surface area of composite figures calculator, how to calculate the area of an object, square footage calculator irregular shape, how do you determine the area of a shape, area of compound figures calculator, area of region calculator, calculate square feet of irregular shape, how do i work out the area of a shape, area of a irregular rectangle calculator, how do i get the area of a shape.
Fish Weight Calculator — Length & Girth to Weight by Species (21 Species, 7 Modes)
Free fish weight calculator: estimate fish weight from length and girth with species-specific formulas (bass, trout, walleye, pike, salmon, redfish, NZ kingfish & more), length-only mode, relative weight (Wr) condition index, reverse weight-to-length, formula comparison, and a catch log. 100% client-side.
Flight Radiation Exposure Calculator — Cosmic Ray Dose per Flight (μSv) — nrtechstudio.com
Free flight radiation calculator: estimate cosmic radiation exposure per flight from duration, cruising altitude and latitude zone. Results as an honest range (μSv and mSv) with chest X-ray and annual background comparisons. Educational estimates only — not medical advice.
Flow Rate Calculator - Q = A·v Solver, Unit Converter, Mass Flow & Tank Fill Time
Free flow rate calculator: solve Q = A·v three ways (flow rate, velocity, or diameter), convert between m³/s, L/s, L/min, GPM, CFM and cfs, compute mass flow ṁ = ρ·Q, and estimate tank fill time t = V
Flyback Converter Calculator — Vout, Duty Cycle & Turns Ratio Solver
Flyback DC-DC converter calculator: compute Vout, duty cycle, or the N2/N1 turns ratio from the ideal CCM formula Vout = Vin·(N2/N1)·D/(1−D). Includes CCM/DCM boundary check and MOSFET & diode stress estimates.
Flywheel Energy Storage Calculator - E = ½Iω², RPM Solver & Material Limit
Free flywheel energy storage calculator: compute stored energy E = ½Iω² for solid disc or rim rotors, solve 3 ways (energy, RPM, or mass), and check the hoop-stress material limit with tip speed. 100%
Foot for Meter Converter
Interactive foot for meter and meter to foot calculator, feet inches to meters centimeters, human height converter, and precision conversion formulas.
Formula Radius of Circle – Diameter & Area Calculator
Formula radius of circle, diameter of a circle formula, circular diameter formula, area of circle equation diameter, how to work out area of a circle using diameter, what is the formula to find diameter of a circle, equation to find the diameter of a circle, formula for calculating diameter of a circle, circle diameter to area, how to find the dimensions of a circle, diameter area calculator.
Fraction To Dec
Convert fractions to decimal values.
Tool - Free Billable Hours Calculator
Interactive weekly work hours timesheet, employee hours tracker, invoice rate calculator, and breakdown of how many hours in a week.
Free-Fall with Air Resistance Calculator — Terminal Velocity & v(t)
Compute terminal velocity, fall speed and distance as a function of time WITH air drag (v(t)=v_t·tanh(gt/v_t)), plus comparison vs vacuum free fall. Free, 100% client-side.
Free Space Path Loss (FSPL) Calculator — 3-Way Solver
Free free space path loss (FSPL) calculator: compute FSPL from distance & frequency, or find distance / frequency from FSPL. Includes a popular-bands table and link budget context. 100% in the browser.
Freight Class Calculator — Density-Based NMFC Class (2025 Scale)
Free freight class calculator: enter weight and box dimensions to get density (lb/ft³) and the NMFC freight class on the current 2025 density scale, plus the legacy 2021 reference scale.
Freq Conv
Convert Hz, kHz, MHz, GHz, and wavelength to frequency.
Frequency Bandwidth Calculator — BW, Q Factor & Fractional BW
Compute frequency bandwidth (BW = f_H − f_L), center frequency f_c, fractional bandwidth, Q factor, and octave conversion. Two-way solver + verified WiFi 20 MHz example. Free, 100% client-side.
Light Frequency Calculator — f = c/λ, Spectrum Colors & EM Bands
Free light frequency calculator: compute f = c/λ or λ = c/f, see spectrum colors (red–violet), EM spectrum bands, photon energy E = hf, and wavenumber.
Fresnel Zone Calculator — R1, R2, R3, 60% Clearance & Distance Solver
Free Fresnel zone calculator: compute Fresnel zone radii 1, 2, 3 (R_n = √(n·λ·d₁·d₂/(d₁+d₂))), check 60% clearance for radio links, and a maximum distance solver. 100% client-side.
Darcy Friction Factor Calculator - Colebrook Solver & Moody Chart
Free Darcy friction factor calculator: solve f from Reynolds number and relative roughness with the iterated Colebrook-White equation, compare Haaland and Swamee-Jain approximations, reverse-solve Re
Froude Number (Fr) Calculator — 3-Way Solver + Regime Classification
Compute the Froude number Fr = v/√(g·L): 3-way solver (Fr, velocity, characteristic length), subcritical/critical/supercritical classification, ship (LWL) & open-channel context. Free, 100% client-side.
Tool - Ft to Cm Converter
High-precision Feet to Centimeters (ft to cm) converter and feet and centimeter engineering calculator with instant bidirectional calculation, visual height comparison, and conversion tables.
Fuel Distance Calculator — How Far Can You Go on a Tank? | nrtechstudio.com
Free fuel distance calculator: enter fuel amount and economy to get maximum driving range in miles or km. Tank presets, reserve-fuel warning, one-way vs round-trip checker, simple EV range mode, MPG to L/100km converter.
Fuel Injector Flow Rate Calculator — Sizing, Pressure Correction & cc/min to lb/hr
Size fuel injectors from target HP and BSFC, correct flow for fuel pressure with the sqrt law, and convert cc/min to lb/hr. BSFC presets labeled by source.
Fuel Mileage Calculator — Real-World MPG & L/100km from Fill-Up Data
Calculate your car's real fuel mileage from fill-up data: distance driven + fuel used = MPG (US/UK), L/100km, km/L. Multi-tank log with honest partial-fill handling, plus fuel cost per km.
G CC to LB FT3 – Density Converter & Mass-Volume Calculator
G cc to lb ft3, g to cm3, lb ft 3 to kg m 3, g cc to kg m 3, g ml to lb in3, kg to cm3, convert g cc to lb ft3, kg per m3, kgs to m3, how to convert g cm3 to lb in3, lbm to ft3, kg m to g cm, 1 g cm 3 to kg m 3, convert gm cm3 to lb in3, convert cm3 to g, m 3 kg to ft3 lb, cm3 to grams calculator, density kg m3, convert meter to kg, lbs gal to kg m3, gr cm3 ke kg m3, how to convert density to grams.
Capital Gains Tax Calculator & Regional Tax Suite
Interactive capital gains tax calculator, stock investment income calculator, Virginia sales tax calculator, and Georgia business tax estimator.
Garden Soil Volume Calculator - Raised Bed, Topsoil, Mulch, Potting Mix
Free garden soil calculator: cubic feet, cubic yards, litres, tonnes & bag counts for raised beds, round beds and custom volumes. 5 materials, soil-mix recipes (Mel's Mix, 60/30/10, hugelkultur) and bulk-vs-bag cost comparison.
Gas Density Calculator (ρ = PM/RT) — Any Gas via Molar Mass
Calculate the density of any gas from pressure, temperature, and molar mass with ρ = P·M/(R·T). Presets O₂, N₂, CO₂, He, H₂, CH₄, dry air + custom molar mass. Output kg/m³, g/L, lb/ft³ + comparison vs air.
Gauss’s Law Calculator — Electric Flux & Field
Electrostatics Gauss’s law calculator: compute electric flux Φ=Q/ε₀, point-charge field E=kQ/r², infinite wire E=λ/(2πε₀r), and infinite plane E=σ/(2ε₀). Two-way solver + field direction explanation.
Gay-Lussac's Law Calculator - P₁/T₁ = P₂/T₂ Solver (Free)
Free Gay-Lussac's law calculator: solve P₁/T₁ = P₂/T₂ for any missing variable. Pressure in Pa, kPa, bar, psi, atm or mmHg; temperature in °C, °F or K (auto-converted to kelvin). Instant results with
Gcd Lcm
Calculate GCD / GCF and LCM with step-by-step solutions.
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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.