Tool Categories

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Numbers show tools available in each category. Some tools fit more than one category.

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Open the details when you want to compare subjects and see a few tools in each.

View category descriptions and tool examples

Calculators

Everyday math, finance, school, and measurement calculators.

61 tools and 61 guides

Basic CalculatorA clean browser calculator for quick arithmetic, percent checks, and copied results.
Percentage CalculatorFind percent-of answers, percent change, discounts, and original values with reverse percentages.
Ratio CalculatorSimplify ratios, scale matching ratios, and split totals by ratio parts.

Converters

Unit, file, color, text, and measurement conversion tools.

7 tools and 7 guides

Conversion CalculatorConvert length, mass, volume, and temperature units with clear formula steps.
Roman Numeral ConverterConvert numbers to Roman numerals and Roman numerals back to numbers.
Shoe Size ConversionConvert foot length into approximate US men, US women, UK, and EU adult shoe sizes.

Text Tools

Word counts, case changes, cleanups, and formatting helpers.

5 tools and 5 guides

Word CounterCount words, characters, sentences, paragraphs, lines, and estimated reading time.
Character CounterCount characters, words, lines, no-space text, and UTF-8 bytes.
Text Case ConverterConvert text across 8 case styles: uppercase, lowercase, title case, sentence case, camelCase, PascalCase, snake_case, and kebab-case.

Date & Time

Date differences, time zones, countdowns, and scheduling helpers.

8 tools and 8 guides

Age CalculatorCalculate exact calendar age in years, months, days, and total days.
Date CalculatorAdd or subtract days from a date, or count full days between two dates.
Time CalculatorAdd or subtract hours, minutes, and seconds with normalized H:M:S, total seconds, and decimal hours.

Finance

Savings, budget, payment, interest, and comparison tools.

85 tools and 85 guides

Mortgage CalculatorEstimate monthly principal, interest, taxes, insurance, PMI, and HOA costs.
Loan CalculatorSolve for monthly payment, loan amount, interest rate, or payoff term for a fixed-rate loan.
Auto Loan CalculatorEstimate a car payment from vehicle price, tax, fees, down payment, trade-in, rate, and term.

Health & Fitness

Simple wellness calculators with clear educational disclaimers.

33 tools and 33 guides

BMI CalculatorEstimate adult body mass index and healthy BMI weight range.
Underweight BMI CalculatorCheck adult BMI against the underweight screening threshold with careful safety notes.
Overweight BMI CalculatorCheck adult BMI against overweight and obesity screening categories.

Home & Projects

Material, room, yard, and building-project estimators for rough planning.

47 tools and 47 guides

Concrete CalculatorEstimate slab volume, cubic yards, cubic meters, and common 40, 60, and 80 lb bag counts.
Roofing CalculatorEstimate roof squares and shingle bundles from footprint, pitch, and waste.
Tile CalculatorEstimate floor, wall, or shower tile count from square feet, tile size, and waste.

Developer Tools

Encoding, formatting, JSON, URL, and productivity utilities.

17 tools and 17 guides

Subnet CalculatorCalculate IPv4 CIDR network, broadcast, mask, wildcard, and usable host range.
Password GeneratorGenerate strong random passwords with length, character sets, and ambiguity controls.
Base64 Encode / DecodeEncode UTF-8 text to Base64 or decode Base64 back to text.

Image Tools

Simple browser-based image helpers for daily creative tasks.

5 tools and 5 guides

Color Contrast CheckerCheck WCAG 2.2 contrast and find a nearby AA-passing text color.
Aspect Ratio CalculatorSimplify aspect ratios and scale width or height while keeping proportions.
Monitor PPI CalculatorCalculate pixels per inch from screen resolution and diagonal size.
Image to Text OCR ToolCopy text from screenshots, labels, receipts, and clear document images without uploading the image.
Image ClassifierClassify an uploaded image in your browser with model confidence notes.

AI Tools

Browser-only AI helpers for text, images, OCR, summaries, and writing checks.

12 tools and 12 guides

AI Token Cost CalculatorEstimate uncached, cached, output, and total AI token costs.
Prompt Token EstimatorEstimate prompt tokens from text length with a visible rough range and tokenizer warning.
Image to Text OCR ToolCopy text from screenshots, labels, receipts, and clear document images without uploading the image.

School & Study

Student-friendly tools for notes, math, timing, and planning.

4 tools and 4 guides

GPA CalculatorEstimate GPA from course credits and letter grades on a common 4.0 scale.
Grade CalculatorFind the final exam grade needed to reach a desired course grade.
Molarity CalculatorCalculate molarity, moles, or grams from final solution volume in liters or milliliters.

Everyday Tools

Quick utilities for ordinary tasks, decisions, and checklists.

23 tools and 23 guides

Random Number GeneratorGenerate random numbers in a custom range, with unique, sorted, and copied results.
Dice RollerRoll one or more virtual dice with custom sides and a modifier.
Four in a Row GamePlay a local four-in-a-row strategy game against a friend or the computer.

Check the assumptions

Construction and electrical tools provide planning estimates. Use the guide to understand what the result leaves out.

Watts to Amps CalculatorUse watts, volts, phase type, and power factor to estimate current. This is not an electrical safety check.Watts to amps guideRead why voltage and phase can change the result, and check the electrical limits before using an estimate around real equipment.Wallpaper CalculatorEstimate rolls from room size, doors, windows, usable roll coverage, and waste percent.Wallpaper calculator guideAllow for pattern repeat when choosing usable coverage and waste. Check the supplier instructions and dye lots before buying rolls.

Free Calculator Resources has links for students, teachers, writers, and community projects.