Start with the type of question you need to solve. These topic groups connect practical calculators with relevant categories, collections, glossary entries, unit converters, and guides. Each link leads to a dedicated page with additional context and assumptions.
Use time and date tools for elapsed time, calendar questions, age, and planning tasks.
Add or subtract hours and minutes to calculate a resulting time duration.
Calculate your exact age in years, months, and days from your birth date.
Find the weekday for any calendar date.
Calculate elapsed time between two times using hours and minutes.
Convert times between any two time zones around the world.
Free date and time calculators for age, date differences, date arithmetic, time zones, countdowns, and durations.
Compare budgets, growth measures, commissions, and sales-tax amounts without interest-based lending or betting tools.
Calculate gross profit and gross margin from revenue and direct costs.
Estimate net profit or loss and net margin from revenue and the costs included in the calculation.
Calculate customer retention using starting customers, new customers gained, and the ending customer count.
Calculate a customer churn rate from the starting customer cohort and the customers lost during a chosen period.
Estimate employee turnover as departures divided by average headcount for a stated reporting period.
Compare actual production or usage with a practical maximum capacity.
Add common monthly income and expenses to estimate the amount left over.
Calculate compound annual growth rate between a starting value and ending value.
Calculate sales commission from a sales amount and commission rate.
Calculate sales tax and final price for any amount and tax rate.
Free business calculators for profit margin, depreciation, unit pricing, ROI, markup, break-even points, and sales commissions.
Free financial calculators for VAT, unit prices, overtime pay, rent splits, tips, discounts, salary, fuel costs, budgeting, inflation, net worth, and total-return metrics.
Understand discounts, percent-off pricing, and how to calculate the amount saved and the final price.
Learn what markup means, how markup is calculated from cost and selling price, and how it differs from margin.
Learn the CAGR formula and how to use it to compare growth over multiple years.
Explore formula-based estimates for nutrition, activity, body measurements, and exercise.
Estimate body surface area using the Mosteller equation from height and weight.
Estimate average pace, split time, and complete split count from distance and elapsed time.
Calculate your daily calorie needs based on activity level and goals.
Calculate your protein, carbohydrate, and fat targets based on your goals.
Estimate one-repetition maximum from a weight and repetitions using the Epley formula.
Calculate your running pace, speed, and time from distance and finish time.
Estimate your pregnancy due date from your last menstrual period.
Calculate waist-to-hip ratio from waist and hip measurements.
Free health and fitness calculators for BMI, calories, body fat, water intake, ideal weight, macros, pace, and pregnancy dates.
Free health and fitness calculators for BMI, BMR, calories, macros, body fat, water intake, ideal weight, waist-to-hip ratio, and pace.
Find tools for arithmetic, fractions, algebra, probability, statistics, geometry, and number notation.
Find a requested nearest-rank percentile from a list of numeric observations.
Calculate the population coefficient of variation from a numeric data set with a positive mean.
Estimate a simple proportion margin of error from sample size, assumed proportion, and a critical z value.
Calculate the mean, median, mode, and range of any set of numbers.
Convert a terminating decimal to a simplified fraction.
Calculate a number raised to a positive, negative, or fractional exponent.
Calculate the factorial of a non-negative integer.
Find the positive factors of a positive integer.
Calculate a logarithm for any positive value and valid base.
Find the median of a list of numbers.
Convert between mixed numbers, improper fractions, and decimal values.
Find the most frequent value or values in a data set.
Convert numbers between binary, decimal, hexadecimal, and octal.
Calculate percent difference between two values using their average magnitude.
Calculate the percentage increase or decrease between two values.
Calculate permutations and combinations for n items taken r at a time.
Check if a number is prime, and find all prime numbers up to any limit.
Calculate simple event probability from favorable outcomes and total outcomes.
Solve a simple proportion with three known values.
Find the hypotenuse of a right triangle from the two perpendicular sides.
Solve a quadratic equation and calculate its discriminant and real roots.
Find the range, minimum, and maximum of a data set.
Simplify ratios, scale ratios, and solve ratio proportions.
Round a number to a selected number of decimal places.
Full scientific calculator with trigonometry, logarithms, exponents, and more.
Convert a number to normalized scientific notation.
Calculate the square root of a non-negative number.
Calculate population or sample standard deviation, variance, mean, sum, and count.
Calculate the quantity or cost per one unit.
Calculate a weighted average from values and their weights.
Calculate the z-score of a value using its mean and standard deviation.
Free math calculators for percentage-point changes, interquartile range, percentages, fractions, ratios, averages, primes, bases, LCM/GCD, Roman numerals, and scientific calculations.
Free math and statistics calculators for percentages, percentage-point change, interquartile range, averages, fractions, probability, standard deviation, z-scores, geometry, equations, and number systems.
Free calculators for students, including grades, GPA, percentages, fractions, interquartile range, averages, probability, statistics, and scientific math.
Browse definitions, formulas, examples, common mistakes, and related calculators.
Understand the difference between percentage change and percentage difference, including when each formula is appropriate.
Estimate shapes, material volumes, surfaces, and practical building quantities from your measurements.
Estimate asphalt volume and approximate mass from paving area, thickness, allowance, and user-entered bulk density.
Estimate fabric roll length from required area, usable roll width, and a cutting-layout efficiency assumption.
Estimate nominal reinforcement-bar mass from diameter, length, and quantity using a standard approximate steel relationship.
Estimate nominal air changes per hour from airflow and room volume.
Calculate the volume and surface area of a cone.
Convert rectangular dimensions in feet to cubic yards.
Estimate flooring area, packages, and material allowance for rectangular spaces.
Estimate gravel volume and an approximate mass from area, depth, and bulk density.
Estimate cubic yards of mulch needed from area and depth.
Estimate paint quantity from surface area, coverage, coats, and waste.
Calculate area and perimeter of a parallelogram.
Estimate the internal volume of a cylindrical pipe from inside diameter and length.
Calculate area, perimeter, and diagonal of a rectangle.
Calculate the volume and surface area of a sphere.
Estimate stair count and riser height from total rise and a target riser height.
Calculate area and perimeter of a trapezoid from its sides and height.
Free construction calculators for square footage, concrete volume, material estimates, and practical building measurements.
Work through basic measurement, energy, mechanics, and electrical relationships using stated units and assumptions.
Calculate the driven-to-driver gear ratio and ideal output speed from tooth counts and input RPM.
Calculate torque magnitude from a perpendicular force and lever arm distance.
Convert a repeating signal frequency to its period, or a period to frequency, using reciprocal relationships.
Estimate the unloaded output voltage of a two-resistor voltage divider.
Calculate average water flow in litres per second and litres per minute from volume and elapsed time.
Estimate a solar array size and panel count from daily energy demand, peak-sun-hours, system efficiency, and panel rating.
Calculate density from mass and volume using density = mass ÷ volume.
Calculate force from mass and acceleration.
Calculate kinetic energy from mass and speed.
Calculate mechanical power from work and time.
Calculate mechanical work from force and displacement.
Calculate voltage, current, or resistance from the other two electrical quantities.
Estimate voltage drop from current, resistance, and optional starting voltage.
Free science and electronics calculators for density, Ohm's law, voltage drop, electrical power, and practical physical relationships.
Free science and electronics calculators for density, electrical power, electricity costs, fuel efficiency, voltage drop, Ohm's law, and practical measurement relationships.
Jump to a common temperature, length, weight, volume, or speed conversion with its own formula and examples.
Convert Celsius to Fahrenheit with a free temperature converter, formula, examples, and common temperatures.
Convert feet to meters with a free feet to meters converter, formula, examples, and common values.
Convert US gallons to liters with a free gallons to liters converter, formula, examples, and common reference values.
Convert grams to ounces with a free grams to ounces converter, formula, examples, and common values.
Convert kilograms to stone with a free kg to stone converter, formula, examples, and reference values.
Convert meters to feet with a free meters to feet converter, formula, examples, and common conversion values.
Convert miles per hour to kilometers per hour with a free mph to km/h converter, formula, examples, and reference values.
Convert ounces to grams with a free ounces to grams converter, formula, examples, and quick reference values.
Open practical utilities for creating passwords, QR codes, and random numbers.
Reduce pixel width and height to a ratio and calculate the pixel diagonal and orientation.
Generate strong, secure passwords with customizable length and character types.
Generate QR codes for URLs, text, email, phone, and WiFi.
Generate random numbers within a custom range, with options for unique values.
Free everyday tools for unit conversion, random numbers, passwords, and QR codes.
Use these simple arithmetic tools to plan charitable giving. Zakat and Zakat al-Fitr rules, thresholds, amounts, and timing can differ by guidance; these tools do not issue religious rulings.
Basic arithmetic estimators for Zakat, Zakat al-Fitr and voluntary giving, with notes about user-supplied local guidance.
Estimate a basic Zakat amount from qualifying net wealth, a user-selected nisab threshold, and the applicable holding-period condition.
Calculate a household total from the locally advised amount per person and the number of people covered.
Plan a voluntary charitable-giving amount from a monthly budget, chosen percentage, and number of months.
Add common monthly income and expenses to estimate the amount left over.
Calculate your net worth by subtracting total liabilities from total assets.
Explore paired-data statistics, sample planning, probability models, vector lengths, coordinate distance, and triangle geometry with stated assumptions.
Calculate the Pearson correlation coefficient for paired numeric observations and see the direction and strength of their linear association.
Fit a simple least-squares line to paired x and y data and estimate a y value for a chosen x.
Estimate a simple random-sample size for a proportion using a chosen confidence z-score, assumed proportion and margin of error.
Calculate the probability of exactly a chosen number of successes in independent trials with the same success probability.
Calculate the magnitude of a two- or three-dimensional vector from its components.
Calculate straight-line distance between two points in a two-dimensional coordinate plane.
Convert an angle between degrees and radians using the exact pi relationship.
Calculate a right triangle hypotenuse and acute angles from its two perpendicular side lengths.
Calculate pyramid volume from the base area and perpendicular height.
Calculate the area between two concentric circles from the outer and inner radii.
Calculate circular arc length and sector area from a radius and central angle in degrees.
Free math and statistics calculators for percentages, percentage-point change, interquartile range, averages, fractions, probability, standard deviation, z-scores, geometry, equations, and number systems.
Free math calculators for percentage-point changes, interquartile range, percentages, fractions, ratios, averages, primes, bases, LCM/GCD, Roman numerals, and scientific calculations.
Calculate basic wave, gas-law, heat, spring, resistor, pipe-flow and efficiency relationships from consistent units. These estimates do not replace qualified design or safety checks.
Estimate average flow velocity in a circular pipe from a volumetric flow rate and internal diameter.
Estimate ideal-gas pressure from amount of gas, absolute temperature and container volume using SI units.
Calculate heat energy for a mass, specific heat capacity and temperature change under a simple constant-capacity assumption.
Calculate ideal spring force magnitude from a spring constant and displacement using Hooke’s law.
Calculate equivalent resistance for two or three resistors connected in parallel.
Calculate wavelength and period from wave speed and frequency when both use consistent SI units.
Compare useful output power with input power and calculate conversion efficiency and losses.
Free science and electronics calculators for density, electrical power, electricity costs, fuel efficiency, voltage drop, Ohm's law, and practical measurement relationships.
Free science and electronics calculators for density, Ohm's law, voltage drop, electrical power, and practical physical relationships.
Estimate pool capacity, wallpaper quantity, fence spacing, garden soil and frustum volumes from measurements you supply. Verify site dimensions and product specifications before purchasing.
Estimate the volume of a circular cone frustum from its two radii and perpendicular height.
Estimate the water capacity of a rectangular pool using length, width and average water depth.
Estimate wall covering area and the number of rolls needed from wall perimeter, height, openings and roll dimensions.
Estimate evenly spaced fence posts and actual spacing from a fence length and desired maximum bay length.
Estimate soil volume for a garden area and layer depth, including an optional waste or settling allowance.
Free home and construction calculators for square footage, roofing, stairs, tile, mulch, gravel, concrete, drywall, decking, and material estimates.
Free construction calculators for square footage, concrete volume, material estimates, and practical building measurements.
Review unit contribution, liquidity, cash conversion, customer value, order value, billable utilization, project completion and simple revenue metrics without lending or interest calculations.
Calculate unit contribution, contribution margin ratio and total contribution from selling price, variable cost and units sold.
Calculate the current ratio and working capital from current assets and current liabilities.
Calculate a simple cash conversion cycle from inventory days, receivable days and payable days.
Estimate gross-profit lifetime value from average revenue per customer, gross margin and an entered customer lifetime.
Calculate average order value from total sales revenue and completed order count for the same period.
Measure billable hours as a share of available working hours over the same reporting period.
Calculate simple task-count completion as a percentage of total project tasks.
Annualize revenue from a short, stated period as a simple pace estimate, assuming that pace remains stable.
Calculate a simple profit-per-employee metric from a reporting-period profit figure and average employee count.
Free business calculators for profit margin, depreciation, unit pricing, ROI, markup, break-even points, and sales commissions.
Free calculators for business and work, including ROI, markup, break-even, sales commission, salary, overtime, VAT, depreciation, profit margin, and practical percentage calculations.
Use straightforward tools for savings rate, rental yield and developer-oriented pixel, rem and compression calculations. Results describe the inputs and assumptions supplied.
Estimate gross and operating net rental yield from annual rent, annual operating costs and property value without financing assumptions.
Calculate the share of take-home income saved during a period, without projecting interest or investment growth.
Convert CSS pixel values to rem and rem values to pixels using a root font size you choose.
Compare original and compressed data sizes to calculate a compression ratio and percentage of space saved.
Free financial calculators for VAT, unit prices, overtime pay, rent splits, tips, discounts, salary, fuel costs, budgeting, inflation, net worth, and total-return metrics.
Free everyday tools for unit conversion, random numbers, passwords, and QR codes.
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