Online calculators and practical tools

Choose a focused calculator for school, money, work, travel, health, construction, images, or development. Every tool works immediately without an account.

113 calculators

Tools

Math and geometry

Percentage Calculator

Solve the most common percentage questions with one calculator and see the equation used for each result.

Percentage Change Calculator

Compare two values with a signed percentage change and distinguish change from simple percentage-point difference.

Fraction Calculator

Calculate with two fractions, reduce the answer automatically, and see the matching decimal value.

Ratio Calculator

Reduce ratios to lowest terms and solve practical scaling or proportion questions.

Average Calculator

Paste comma- or space-separated values and get the main descriptive statistics immediately.

Standard Deviation Calculator

Compare sample and population spread with the calculation inputs kept visible.

Quadratic Formula Calculator

Enter three coefficients to solve ax2 + bx + c = 0 and inspect the discriminant.

Prime Factorization Calculator

Break an integer into prime powers and list its positive factors.

Triangle Calculator

Validate three sides and return a complete triangle measurement set.

Circle Calculator

Choose the known circle measurement and calculate every related dimension.

Rectangle Calculator

Measure a rectangle and see all core dimensions from two side lengths.

Volume Calculator

Select a 3D shape, enter its dimensions, and calculate volume with the formula shown.

Pythagorean Theorem Calculator

Enter any two right-triangle sides and solve for the third with validation.

Slope Calculator

Enter two points to calculate the line relationship and coordinate geometry values.

Random Number Generator

Draw reproducible-size number sets using cryptographically secure browser randomness.

Tools

Finance and money

Loan Calculator

Model principal, interest rate, and term with a month-by-month balance schedule.

Mortgage Calculator

Separate principal and interest from estimated monthly housing costs.

Compound Interest Calculator

Project ending balance and separate deposits from earned interest.

Savings Goal Calculator

Turn a target amount and deadline into a practical monthly saving requirement.

Discount Calculator

See exactly how much a discount saves and what the checkout price becomes.

Markup and Margin Calculator

Compare markup on cost with margin on revenue without confusing the two percentages.

Tip Calculator

Split a bill cleanly while showing tip and total amounts for the group and each person.

Sales Tax Calculator

Switch between tax-exclusive and tax-inclusive calculations with a custom rate.

Currency Converter

Compare major currencies and keep the rate source and update status visible.

Tools

Grades and education

Grade Calculator

Add assignments, enter points earned and available, and get the exact point-based course percentage.

Weighted Grade Calculator

Model exams, homework, projects, and other categories with independent percentages and weights.

Final Grade Calculator

Enter your current grade, the final exam weight, and the target grade to calculate the required exam score.

GPA Calculator

Combine course credits and grade points, with a clear scale table and no hidden rounding.

Easy Grader

Create a printable teacher grading table with decimal precision and configurable letter-grade thresholds.

Grading Scale Calculator

Model nonstandard course cutoffs against either points earned or a direct percentage.

Tools

Time and date

Time Zone Converter

Choose real city-based time zones and convert a specific local time using the offset in effect on that date.

World Clock

Keep a compact live list of important cities and see date boundaries and current offsets at a glance.

Meeting Time Planner

Scan a 24-hour timeline across several cities with working-hour highlighting and date changes made explicit.

Military Time Converter

Enter either format, handle midnight and noon correctly, and copy the normalized result.

Unix Time Converter

Detect seconds versus milliseconds, convert in both directions, and keep UTC explicit.

Date Duration Calculator

Compare two dates with both absolute elapsed time and a human calendar breakdown.

Date Calculator

Move forward or backward from a date while preserving real calendar month lengths.

Age Calculator

Get calendar age plus total elapsed months, weeks, and days without averaging month lengths.

Business Days Calculator

Calculate Monday-through-Friday working days with optional endpoint inclusion.

Online Stopwatch

Track elapsed time against a monotonic browser clock without losing progress when rendering slows.

Week Number Calculator

Translate any calendar date into planning-friendly week, day, and quarter references.

Moon Phase Calculator

Place a date within the 29.53-day synodic cycle and visualize the approximate lunar phase.

Sunrise and Sunset Calculator

Get coordinate-based solar times with polar-day and polar-night detection.

US Federal Holiday Calculator

Generate a year-specific reference table and download the dates as CSV.

Countdown Timer

Choose a target moment and keep a live, copy-ready countdown in the browser.

Hours Calculator

Turn a work interval into decimal hours and clock time without manual borrowing.

Tools

Health and fitness

Running Split Calculator

Turn a target finish time into cumulative checkpoint times and individual segment splits.

Stone and Pounds Converter

Handle values such as 11 st 6 lb directly instead of converting each part separately.

BMI Calculator

Convert height and weight into BMI and a reference weight range for that height.

BMR Calculator

Use the Mifflin-St Jeor equation and compare activity-adjusted maintenance estimates.

Calorie Calculator

Start with estimated daily energy use and compare moderate calorie adjustments.

Ideal Weight Calculator

See several formula estimates side by side instead of presenting one number as universal.

Body Fat Calculator

Enter height, neck, waist, and optional hip measurements with consistent units.

Tools

Everyday

Running Pace Calculator

Link distance and elapsed time to per-kilometer and per-mile pace, speed, and common race projections.

Fuel Economy Converter

Handle reciprocal fuel-consumption units correctly and keep US and Imperial gallons separate.

Cooking Measurement Converter

Move between cups, spoons, milliliters, ounces, and grams while making ingredient assumptions visible.

Recipe Scaler

Resize every ingredient together and display practical reduced fractions for kitchen use.

Trip Cost Calculator

Compare the complete driving cost rather than fuel alone, with MPG or L/100 km input.

Electricity Cost Calculator

Translate a device power rating into practical kilowatt-hours and estimated utility cost.

Tools

Construction and home

Electrical Load Calculator

Add common loads and see calculated amps, adjusted demand, remaining capacity, and overload status.

BTU Calculator

Create a transparent first-pass HVAC size range with every adjustment shown.

Concrete Calculator

Enter slab dimensions and waste allowance to plan concrete volume and common bag counts.

Paint Calculator

Plan paint quantity for a room while subtracting doors and windows.

Tile Calculator

Estimate whole tiles, covered area, and purchase quantity for a rectangular surface.

Flooring Calculator

Turn room dimensions into a rounded-up flooring purchase quantity.

Board Foot Calculator

Estimate dimensional lumber volume with both nominal measurements and total cost.

Tools

Developer and data

Color Converter

Keep formats synchronized, preview the actual color, and check text contrast against white and black.

Text Encoding Converter

Transform Unicode text locally with explicit UTF-8 handling and copy-ready output.

Roman Numeral Converter

Convert in either direction and validate canonical subtractive notation.

URL Parser

Inspect encoded links and repeated query parameters using the browser URL standard.

JWT Decoder

Read base64url JWT contents and expiration timing while keeping signature verification clearly separate.

Password Generator

Create one or many strong passwords locally with the browser secure-random API.

QR Code Generator

Preview and download a crisp PNG QR code generated entirely in the browser.

Ohm's Law Calculator

Solve the complete V-I-R-P relationship with unit scaling and formula checks.

Aspect Ratio Calculator

Lock image or screen proportions and solve a missing output dimension.

DPI and PPI Calculator

Connect pixels to inches or centimeters for screens and print planning.

Resistor Color Code Calculator

Choose colored bands and read the resistance in ohms, kilohms, or megohms.

IPv4 Subnet Calculator

Enter an IPv4 address and prefix to inspect the complete subnet boundaries.

JSON Formatter and Validator

Paste JSON, check its syntax, and produce readable or compact output.

UUID Generator

Create standards-shaped random identifiers locally with bulk output.

Hash Generator

Create a hexadecimal message digest locally and compare exact text inputs.

Tools

Image tools

Image Cropper

Set a precise crop rectangle, keep it within image bounds, and export the result in a chosen format.

Image Rotator and Flipper

Correct image orientation with a live preview while retaining full source dimensions.

Image Watermark Tool

Preview a readable watermark at the final image resolution and export it locally.

Image Background Remover

Remove white or other uniform backgrounds locally with a transparent PNG preview.

Batch Image Compressor

Apply one width, format, and quality policy to an entire image set with per-file size results.

Image Resizer

Choose an image, set width or height, preview the result, and download the resized file.

Image Compressor

Tune JPEG or WebP quality while previewing dimensions and estimated file savings.

Image Format Converter

Change an image format without uploading the image to a remote conversion service.

Tools