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.
10 Binary Number & Numeral Systems Converter
Free online decimal to binary converter with step-by-step division, base 5 calculator, numeral systems converter, and binary conversion charts.
100 Amp Wire Size Calculator — NEC Table 310.16 Ampacity
What size wire for 100 amps? NEC Table 310.16 ampacity calculator: copper vs aluminum, 60/75/90°C columns, conduit derating, and breaker recommendation. Free, no sign-up.
3D Print Cost Calculator (FDM + Resin) — Free Print Quoting Tool
Free 3D print cost calculator for FDM & resin. Model filament, electricity, machine wear, labor, support & purge waste, failure rate and quoting margin — all in your browser.
A-Frame Size Calculator — 7 Ways to Size Your A-Frame Cabin
Free 7-mode A-frame cabin size calculator: triangle geometry, usable floor (5 ft rule), loft, deck, kitchen/bath fit, occupants, snow-load rafter chec
A/B Test Calculator: Significance Test and Sample Size Planner | NRTechStudio
Free A/B test calculator: enter visitors and conversions for variants A and B to get conversion rates, uplift, a two-proportion z-test p-value, a significant-or-not verdict, and the confidence interval — plus a sample size planner.
Absolute Difference Calculator |a−b| + Steps
Free absolute difference calculator: enter two numbers to get |a−b| with step-by-step breakdown, worked examples, and how it differs from percent difference.
Absolute Value Calculator - Find |x| with Number Line
Free absolute value calculator: enter x to get |x|, see the piecewise definition (|x| = x for x >= 0, |x| = -x for x < 0), worked steps, a number line showing x and |x|, and key properties.
AC Wattage Calculator — Real, Apparent & Reactive Power (1-Phase, 3-Phase, PF Correction)
Free AC wattage calculator: solve P=V×I×PF for any missing variable, 3-phase power (√3×V_LL×I×PF), and size power-factor correction capacitors. Real (W), apparent (VA), reactive (VAR).
Web Accessibility & Contrast Ratio Checker
Free web accessibility checker and WCAG contrast ratio checker. Verify colour contrast accessibility, test Section 508 compliance, and preview text legibility.
Add Times Calculator - Sum Hours, Minutes and Seconds Online
Free add times calculator: add and subtract hours, minutes and seconds in a list, get the total, average, decimal hours and minutes. Perfect for timesheets and payroll.
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.
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
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.
Interest-Only Loan Amortization Calculator
Interactive financial calculator generating complete amortization tables for interest-only loans, personal loans, and deferred payment loans.
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.
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 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.
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.
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
Appliance Depreciation Calculator (Straight-Line & Declining Balance) | NR Tech Studio
Calculate household appliance depreciation with straight-line and double-declining balance methods, with a year-by-year book value schedule.
Appliance Energy Cost Calculator — kWh, Bill Builder & LED Savings
Free appliance energy cost calculator: 60+ appliance wattage database, multi-appliance bill builder, vampire/standby power mode, LED savings calculator, meter-reading mode, and a custom tiered-tariff (slab) builder. 100% in your browser.
Aquarium Calculator — Tank Volume, Fish Stocking, Glass Thickness & Dosing (Free)
Free aquarium calculator suite: fish tank volume in liters & gallons (rectangular, bow front, cylinder), stocking guide (inch-per-gallon + surface area), glass & acrylic thickness estimator, water change, dechlorinator, salt & medication dosing, heater size and substrate. 100% client-side, no signup.
Aquarium CO2 Calculator — Bubble Rate, pH/KH ppm, Cylinder Duration & Drop Checker
Free aquarium CO2 calculator suite: Dennerle bubble-rate starter for planted tanks, pH/KH to CO2 ppm chart, CO2 cylinder duration estimator (how long your tank lasts), drop checker color guide, liquid carbon dosing & CO2 schedule. 100% client-side, no signup.
Aquarium Flow Calculator — Turnover, Return Pump, Sump Drain-Back & Wavemaker Planner
Free aquarium flow calculator suite: turnover rate planner (GPH/LPH), return pump sizer with head loss, power-outage sump drain-back flood checker, and wavemaker placement guide. 100% client-side, no signup.
Area and Volume Formulas Calculator
Interactive geometry solver for area and volume formulas, 3D shapes surface area, and composite shapes volume calculations.
Tool - Area Formulas for Shapes Calculator
Interactive 2D & 3D geometry calculator and formula guide for finding area, surface area, and volume across all geometric figures.
Trapezoid Area Calculator (Area of a Trapezoid) + Diagram & Steps
Free online trapezoid area calculator: compute area A = (a+b)/2 × h from parallel sides + height, or from 4 sides (height derived from legs). cm/m/in/ft conversion, perimeter, SVG diagram, and calculation steps.
Area of Half a Circle Calculator & Semi Circle Studio
Interactive area of half a circle calculator and semi circle calculator with radius, diameter, arc length, and perimeter.
Area of Irregular Polygon Calculator
Interactive Draw a Shape and Calculate Area, Shoelace Formula, Land Dimensions, and Square Foot Calculator.
Area to Volume & 3D Solid Calculator
Precision area to volume calculator, 3D solid geometry solver, L x W x H rectangle volume, triangular prism, and volume-to-weight conversion engine.
Area & Volume Calculator Online
Free online area calculator for irregular shapes, composite shapes, compound shapes. Surface area volume calculator, volume formula calculator, area formula calculator with step-by-step results.
Arithmetic Calculator & Rounding Calculator
Full-featured arithmetic calculator with rounding calculator, order of operations, history log, and unit-aware number formatting.
ASCII Calculator & Converter
Free online ASCII calculator, hex reader, ASCII translator, and text encoding converter. Convert text to ASCII codes, hex, binary, and Unicode code points.
Aspect Ratio Calculator & Image Resizer
Free online aspect ratio calculator to compute dimensions (16:9, 4:3, 21:9, 1:1, 9:16) for videos, photography, displays, and web design.
Atoms to Moles Calculator — Atoms, Molecules & Grams Converter
Free atoms to moles calculator: convert atoms, molecules, ions and formula units to moles (and back), plus grams to moles via molar mass. Uses the exact Avogadro constant. 100% client-side.
Audio File Size Calculator & Sound Storage Studio
Interactive audio file size calculator and sound file size calculator for music producers, podcasters, and sound engineers.
Audiobook Speed Calculator — Listening Time at Any Playback Speed
Free audiobook speed calculator: enter a book's length at 1x and a playback speed (0.75x–3x) to get actual listening time, time saved, and an estimated finish date.
Auto Insurance Calculator — State Minimum Limits, Premium Estimator & Coverage Advisor (No Sign-Up)
Free auto insurance calculator: 50-state minimum liability limits table, no-sign-up premium estimator by state/age/vehicle/record, coverage advisor (how much do I need), teen driver & EV modes, plus Ontario/BC/UK/AU. Educational estimates, 100% client-side.
Tool - Auto Loan Amortization Schedule & Car Payment Calculator
Universal automotive loan calculator, car payment interest calculator, vehicle loan amortization schedule, and loan payoff equation solver.
Tool - Average and Standard Deviation Calculator
High-precision statistical analysis suite featuring average and standard deviation calculator, summary statistics calculator, p-value from t-score calculator, and frequency distribution mean solver.
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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.