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Free online calculators, unit converters, and mathematical tools with clear working and step-by-step formulas.

Comprehensive searchable library of all math, algebra, geometry, finance, science, and conversion tools.

Fast, accurate conversions across length, mass, temperature, area, volume, time, and engineering units.

Deep-dive educational guides explaining percentages, compound interest, roots, precision, and statistical spread.

Articles, tutorials, calculation guides, and worked examples from the Convert & Count editorial team.

Fast, ad-free mobile calculation companion for Android devices with instant offline access.

Our editorial philosophy, calculation accuracy standards, methodology, and publishing team.

Detailed technical documentation on precision standards, numeric models, rounding rules, and limitations.

Our commitment to reader privacy, cookie minimization, and no tracking of personal numbers or calculations.

Usage terms, informational disclaimers, and guidelines for financial and academic verification.

Complete, real-time hierarchical index of all pages, calculators, guides, and articles.

Master geometric reflections step-by-step. Learn reflection formulas for axes and custom lines, rules for coordinates and shapes, and how to use an online reflection calculator.

Learn the percentage change formula step-by-step, see real-world examples, and avoid the most common mistakes people make when calculating increase or decrease.

Everything public employees need to know before relying on a 457 calculator — from catch-up rules and Roth options to loans, RMDs, and pairing it with a pension.

Confused converting units? A clear guide to metric vs. imperial conversions — length, temperature, mass, volume, and more — with tools to get it exact.

Understand return conventions, contribution timing, and what a model leaves out.

Visual guide to boundaries, surface space, and capacity — from floor tiling to shipping box capacity.

Never wonder whether to multiply or divide again. Use the unit factor canceling method for flawless conversions.

Understand how interest on interest accelerates your savings and why compounding frequency matters over long horizons.

How to graph straight lines, interpret slope as a practical rate of change, and find parallel or perpendicular lines.

Why viral math equations cause internet arguments and how calculators parse order of operations.

How scientists write astronomical distances and atomic scales, plus rules for rounding measured precision.

Learn how standard deviation quantifies volatility and consistency across exam scores, investments, and experiments.

Master percentage formulas for shopping discounts, salary raises, profit margins, and reversing sales tax.

Walk through a small data set and see what average distance really means.

Demystify why mortgage and auto loan payments are frontloaded with interest and how extra principal saves thousands.

How to compare measurements from two completely different distributions using normalized z-scores.

Fractions, rounding, and the small details that matter when reading a result.

Connect graphical x-intercepts with algebraic roots using factoring, the quadratic formula, and iterative solvers.

Raise a real number to the power of 10.

Raise a real number to the power of 11.

Raise a real number to the power of 12.

Raise a real number to the power of 13.

Raise a real number to the power of 14.

Raise a real number to the power of 15.

Raise a real number to the power of 16.

Raise a real number to the power of 17.

Find the nonnegative distance of a number from zero.

Add multiple decimals exactly, with aligned place-value working.

Find the arithmetic mean of a list of numbers.

Count unordered selections of r items from n.

Convert a decimal to a simplified fraction.

Convert a decimal value into a percentage.

Raise a base number to a chosen exponent.

Calculate n! for a nonnegative whole number.

Evaluate everyday arithmetic with parentheses and exact fraction results.

Add two fractions and return a simplified exact fraction.

Divide one fraction by another and simplify the exact result.

Multiply two fractions and simplify the exact result.

Subtract one fraction from another and simplify the result.

Convert a numerator and denominator into a decimal.

Convert a fraction into a percentage.

Find the greatest common divisor of two whole numbers.

Find the geometric mean of positive values.

Find the harmonic mean of positive values.

Add, subtract, multiply, and divide signed integers with exact results.

Find principal arcsin, arccos, and arctan angles in degrees or radians.

Find the least common multiple of two whole numbers.

Graph a shifted logarithm and inspect its domain and intercept.

Calculate a logarithm using any valid positive base.

Find mean absolute deviation, the average, and a complete deviation table.

Convert a mixed number into a simplified improper fraction.

Find the real nth root of a number.

Sort numbers and fractions, or plot a simple interval or inequality.

Calculate a percentage of any number.

Convert a percentage into decimal form.

Find what percentage one number is of another.

Measure the percent increase or decrease from an old value to a new value.

Compare two values using their average magnitude as the reference.

Compare a measured value with an accepted value as a percentage error.

Count ordered selections of r items from n.

Break a positive integer into its prime factors.

Check whether a positive whole number is prime.

Solve a proportion of the form a/b = c/x.

Reduce a two-number ratio to its simplest whole-number form.

Express a ratio a:b as a percentage of b.

Find the reciprocal of a whole number, decimal, or fraction.

Find the quotient and remainder for integer division.

Calculate the RMS value of a list of numbers.

Round a number to a selected number of decimal places.

Express a number in scientific notation.

Round a number to a chosen number of significant figures.

Turn a whole-number square root into its simplest radical form.

Square a number or fraction and see the exact multiplication.

Calculate 1³ + 2³ + … + n³.

Find 1 + 2 + … + n without listing every term.

Calculate 1² + 2² + … + n².

Graph transformed sine, cosine, or tangent with explicit angle units.

Convert a quantity pair into an amount per one unit.

Calculate a weighted mean from three values and their weights.

Find the nth term of an arithmetic sequence.

Find the sum of the first n terms of an arithmetic sequence.

Get radius and area from (x − h)² + (y − k)² = r².

Expand f(g(x)) or g(f(x)) for polynomial inputs and evaluate a point.

Find the constant k in y = kx and project another value.

Calculate b² − 4ac and classify the real roots of a quadratic.

Find straight-line distance between two coordinate points.

Estimate doubling time from a constant compound growth rate.

Project a starting value using a constant percentage decay rate.

Project a starting value using a constant percentage growth rate.

Find the nth term of a geometric sequence.

Find the sum of the first n terms of a geometric sequence.

Find the remaining quantity after a number of half-lives.

Convert simple inequalities and interval unions into clear notation.

Solve an equation of the form ax + b = c.

Estimate y at an x-value between or beyond two known points.

Find the point exactly halfway between two coordinates.

Test whether a relation is a function and list its domain and range.

Find a quadratic vertex, roots, axis, focus, and directrix.

Find the shortest distance from a point to Ax + By + C = 0.

Build a point-slope equation from a point and slope.

Evaluate ax³ + bx² + cx + d at a chosen x value.

Solve ax² + bx + c = 0 and inspect its discriminant.

Find the vertex of y = ax² + bx + c.

Find domain exclusions, holes, intercepts, and asymptotes for quadratic ratios.

Find the slope between two coordinate points.

Find y = mx + b from two distinct points.

Find the slope of a line written Ax + By = C.

Solve three linear equations and identify inconsistent or dependent systems.

Solve two linear equations in x and y.

Find real polynomial roots through degree 6, plus quadratic complex roots.

Estimate a 80% confidence margin for a mean when population standard deviation is supplied.

Estimate a 85% confidence margin for a mean when population standard deviation is supplied.

Estimate a 90% confidence margin for a mean when population standard deviation is supplied.

Calculate exact, cumulative, at-least, and between probabilities.

Compare standard deviation with the magnitude of the mean.

Calculate a signed independent-group effect size using pooled standard deviation.

Calculate Pearson’s r from paired x and y values.

Calculate the weighted expected value of discrete outcomes.

Calculate the probability that two independent events both occur.

Fit a least-squares line y = mx + b to paired data.

Build a z-based confidence interval for a mean from mean, known standard deviation, and sample size.

Find common measures of center for a list of numbers.

Find the middle value of a numeric data set.

Find the most frequently occurring value or values.

Estimate a percentile value from a data set using linear interpolation.

Estimate the percentage of observations at or below a chosen value.

Calculate P(A ∪ B) when P(A), P(B), and their overlap are known.

Find Q1, median, Q3, and the interquartile range.

Find the minimum, maximum, and range of a data set.

Calculate sample or population standard deviation.

Estimate the standard error of the sample mean from raw observations.

Calculate population or sample variance for a data set.

Standardize a value using a mean and standard deviation.

Find the area between two concentric circles.

Calculate circular arc length from radius and central angle.

Calculate circle area, circumference, and diameter from radius.

Find chord length from circle radius and central angle.

Estimate minor-segment area from radius and central angle.

Find a cone’s slant height from radius and vertical height.

Find total surface area of a right circular cone.

Calculate the volume of a right circular cone.

Calculate cube volume, surface area, and space diagonal.

Calculate cylinder volume and total surface area.

Find total surface area of a closed cylinder.

Find ellipse area from the semi-major and semi-minor axes.

Approximate ellipse circumference with Ramanujan’s formula.

Calculate the volume of a hemisphere.

Calculate parallelogram area from base and perpendicular height.

Find the hypotenuse from two perpendicular legs.

Calculate rectangle area, perimeter, and diagonal.

Find the diagonal of a rectangle from width and height.

Calculate box volume, surface area, and space diagonal.

Reflect points across an axis, a diagonal, or a custom straight line.

Calculate regular polygon area from side count and side length.

Find each interior angle and the total interior-angle sum of a regular polygon.

Calculate rhombus area from its two diagonals.

Calculate a right triangle’s hypotenuse, area, and acute angles from two legs.

Rotate coordinate points around any center, with a visual comparison.

Calculate the area of a circular sector from radius and central angle.

Calculate arc length plus two radii for a circular sector.

Calculate the surface area of a sphere.

Calculate the volume of a sphere from its radius.

Calculate square area, perimeter, and diagonal from a side length.

Calculate volume from base side length and vertical height.

Find trapezoid area from two parallel bases and height.

Find triangle area from a base and perpendicular height.

Calculate a triangle perimeter from three side lengths.

Calculate prism volume from triangle base, triangle height, and prism length.

Calculate ideal buoyant force from fluid density and displaced volume.

Calculate mass density from mass and volume.

Calculate electrical power from voltage and current.

Calculate net force from mass and acceleration.

Calculate near-Earth gravitational potential energy.

Calculate near-Earth gravitational potential energy.

Find height from gravitational potential energy.

Calculate gauge pressure from liquid density, gravity and depth.

Solve constant-acceleration displacement, velocity, acceleration, and time.

Calculate kinetic energy from mass and speed.

Calculate kinetic energy from mass and speed.

Find mass from kinetic energy and speed.

Calculate average power from work and elapsed time.

Calculate linear momentum from mass and velocity.

Calculate voltage from current and resistance.

Estimate flight time, range, peak height, and the ideal trajectory.

Calculate average speed from distance and elapsed time.

Find speed from kinetic energy and mass.

Calculate wavelength from wave speed and frequency.

Calculate mechanical work for force applied along the displacement direction.

Find signed integrals and total geometric area for polynomial curves.

Project cell count for bacterial culture growth from a starting value, periodic growth rate, and number of periods.

Project population for exponential population growth from a starting value, periodic growth rate, and number of periods.

Find the periodic growth rate needed for exponential population growth to move from the starting value to the target value.

Calculate final concentration after dilution.

Calculate stock volume needed for a target dilution.

Calculate moles from pressure, volume and temperature.

Calculate baseboard length for baseboard from room perimeter and coverage factor.

Calculate brick count estimate for brick wall from wall area and bricks per square meter.

Calculate concrete volume for concrete slab from slab area and thickness.

Calculate emissions for carbon emissions from activity amount and emission factor.

Calculate emissions for electricity carbon from electricity use and grid emission factor.

Calculate emissions for fuel carbon from fuel used and emission factor.

Calculate coffee cost for coffee habit cost from cups and cost per cup.

Calculate commute cost for commute cost from trips and cost per trip.

Calculate energy cost for electricity cost from energy use and price per kwh.

Calculate ingredient weight for bakers percentage from flour weight and bakers percent decimal.

Calculate batch cost for batch cost from ingredient units and cost per unit.

Calculate total carbohydrate for carbohydrate batch from servings and carbs per serving.

Calculate 100% of an entered maximum heart rate for training reference.

Calculate 50% of an entered maximum heart rate for training reference.

Calculate 55% of an entered maximum heart rate for training reference.

Calculate BMI from body mass and height.

Estimate body surface area with the Mosteller formula.

Calculate your bowling handicap per game, 3-game series totals, and adjusted scores from your average, basis score, and league percentage.

Calculate cadence for cadence from revolutions divided by time.

Calculate average speed for cycling speed from distance divided by time.

Calculate power to weight for power to weight from power divided by body mass.

Calculate average rate for api requests from total amount divided by count.

Calculate average rate for audio samples from total amount divided by count.

Calculate average rate for backup data from total amount divided by count.

Calculate commission for affiliate campaign from conversions and commission per conversion.

Estimate affiliate earnings from clicks, conversion rate, order value, and commission rate.

Estimate the number of units needed to cover fixed costs.

Calculate compound annual growth rate between a start and end value.

Calculate commission earnings from sales and commission rate.

Calculate commission earned for commission sales from sales amount and commission rate decimal.

Project growth with a fixed rate and compounding frequency.

Calculate project revenue for consulting engagement from consulting hours and hourly fee.

Calculate contribution margin per unit and as a percentage of sales.

Calculate course revenue for course sales from enrollments and price per enrollment.

Calculate delivery revenue for delivery business from deliveries and revenue per delivery.

Calculate a sale price and amount saved from a percentage discount.

Calculate ad cost for display advertising from impressions and cost per impression.

Calculate sales revenue for ecommerce orders from orders and average order value.

Calculate ticket revenue for event ticket sales from tickets sold and ticket price.

Project a lump sum using a fixed compound return.

Explore savings coverage using your spending, income, inflation, and return assumptions.

Estimate a fixed monthly payment for a standard amortizing loan.

Calculate selling price from cost and markup percentage.

Project a future balance or solve for the monthly deposit needed for a target.

Estimate monthly principal-and-interest payment for a fixed-rate mortgage.

Estimate gross weekly pay with regular and overtime hours.

Estimate revenue per thousand pageviews.

Discount a future amount back to today using a fixed rate.

Calculate gross margin percentage from cost and selling price.

Calculate return on ad spend from revenue and advertising cost.

Calculate simple return on investment from initial and final values.

Convert annual salary to an approximate hourly rate.

Add a user-entered sales-tax rate to a pre-tax amount.

Estimate interest and ending balance without compounding.

Split a bill plus tip evenly among a number of people.

Calculate tip amount and total bill from a chosen percentage.

Model a hypothetical 403(b) balance from the contributions and returns you choose.

Model a hypothetical 457(b) balance from the contributions and returns you choose.

Model a hypothetical TSP balance from the contributions and returns you choose.

Compare reinvested dividends with keeping distributions as cash.

Estimate annual dividend income and its average monthly equivalent.

Explore a hypothetical investment scenario without live prices or return claims.

A manual-withholding worksheet for your Connecticut paycheck; tax amounts must be entered.

A manual-withholding worksheet for your Georgia paycheck; tax amounts must be entered.

A manual-withholding worksheet for your Kentucky paycheck; tax amounts must be entered.

A manual-withholding worksheet for your Louisiana paycheck; tax amounts must be entered.

A manual-withholding worksheet for your Maryland paycheck; tax amounts must be entered.

A manual-withholding worksheet for your Massachusetts paycheck; tax amounts must be entered.

A manual-withholding worksheet for your Missouri paycheck; tax amounts must be entered.

A manual-withholding worksheet for your Ohio paycheck; tax amounts must be entered.

A manual-withholding worksheet for your Oklahoma paycheck; tax amounts must be entered.

A manual-withholding worksheet for your Virginia paycheck; tax amounts must be entered.

Convert absorbed radiation dose units.

Convert acceleration units.

Convert moles and common SI-prefixed amount units.

Convert degrees, radians, gradians, and turns.

Convert angular acceleration units.

Convert radians per second, degrees per second, RPM, and revolutions per second.

Convert area units with a clear result and a complete equivalence table.

Convert capacitance units by SI prefix.

Convert centimeter values to foot using the standard length conversion factor.

Convert centimeter values to inch using the standard length conversion factor.

Convert centimeter values to micrometer using the standard length conversion factor.

Convert centimeter values to mile using the standard length conversion factor.

Convert centimeter values to millimeter using the standard length conversion factor.

Convert common kitchen volume measurements.

Convert decimal and binary digital storage units.

Convert common network and data-transfer rates.

Convert density units.

Convert dynamic viscosity units.

Convert electric charge units.

Convert amperes and common SI-prefixed current units.

Convert electric field strength units.

Convert siemens and common SI-prefixed conductance units.

Convert siemens-per-meter conductivity units.

Convert electrical resistance units by SI prefix.

Convert electrical resistivity units.

Convert energy and work units.

Convert joules per cubic meter and related units.

Convert entropy units.

Convert equivalent-dose units.

Convert volumetric flow-rate units.

Convert force units.

Convert frequency units.

Convert fuel economy between mpg, km/L, and L/100 km.

Convert heat-flow density units.

Convert heat-transfer coefficient units.

Convert illuminance units.

Convert inductance units by SI prefix.

Convert common jerk units.

Convert kinematic viscosity units.

Convert length units with a clear result and a complete equivalence table.

Convert electric charge per unit length.

Convert luminance units.

Convert lumens and related luminous-flux scales.

Convert magnetic flux density units.

Convert webers, milliwebers, microwebers, and maxwells.

Convert mass-per-volume concentration units.

Convert kilograms per second and common mass-flow units.

Convert molarity-scale concentration units.

Convert amount-of-substance flow rates.

Convert mass moment of inertia units.

Convert power units.

Convert pressure units.

Convert pressure change per unit length.

Convert activity units for radioactive decay.

Convert running pace between minutes per kilometer and minutes per mile.

Convert specific heat capacity units.

Convert volume-per-mass units.

Convert speed and velocity units.

Convert spring-rate / stiffness units.

Convert electric charge per unit area.

Convert newtons per meter and related surface-tension units.

Convert temperature units with a clear result and a complete equivalence table.

Convert temperature intervals without absolute-temperature offsets.

Convert common thermal-conductivity units.

Convert common duration units.

Convert torque units.

Convert common print and typography length units.

Convert electric potential units by SI prefix.

Convert electric charge per unit volume.

Convert liquid and solid volume units.

Convert mass units with a clear result and a complete equivalence table.

Add or subtract a whole number of days from a calendar date.

Calculate age between a birth date and another date.

Average elapsed durations and see their total, minimum, and maximum.

Find elapsed days and calendar components between two dates.

Convert a decimal-hour duration into hours and minutes.

Convert hours and minutes into decimal hours.