Browse the full ERICH Calculators directory. Every calculator works in your browser and is free to use.
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29 calculators · Loans, savings, interest and everyday money decisions
19 calculators · Pricing, profitability, marketing and performance
37 calculators · Percentages, algebra, geometry and statistics
16 calculators · Ages, date differences, workdays and time
27 calculators · Materials, measurements and project estimates
8 calculators · Grades, GPA, test scores and classroom math
14 calculators · BMI, energy, strength, body metrics and fitness estimates
20 calculators · Length, weight, volume, temperature and unit conversions
12 calculators · Fuel, MPG, EV charging, tires and road-trip tools
10 calculators · Geometry, statistics, physics and chemistry
10 calculators · ZIP, cost-of-living, currency and geographic data
All calculators listed alphabetically for fast scanning.
Calculate age in years, months and days from a birth date to a selected date.
Convert length, weight, area, volume, temperature, speed, pressure, energy and digital storage from one tool.
Calculate a payment and full schedule showing principal, interest, remaining balance and extra principal.
Convert hourly, weekly, biweekly, semimonthly or monthly gross pay into an estimated annual income.
Calculate APY from a nominal annual rate and compounding frequency and estimate one year of interest.
Calculate area for a rectangle, triangle, circle or trapezoid from the dimensions you enter.
Convert area between square feet, square meters, acres, hectares, square miles and other common units.
Estimate asphalt volume and tons from area, compacted depth and material density.
Estimate a vehicle lease payment from capitalized cost, residual value, money factor, term and tax.
Estimate an auto loan payment after down payment, trade-in and sales tax.
Find the arithmetic mean of a comma-separated list of numbers.
Compare a standard monthly mortgage schedule with an accelerated biweekly payment approach.
Estimate body mass index from height and weight using the standard adult BMI formula.
Estimate basal metabolic rate using the Mifflin–St Jeor equation.
Calculate lumber board feet from thickness, width, length and quantity.
Estimate adult body-fat percentage from body measurements using the U.S. Navy circumference method.
Estimate body surface area using the Mosteller formula.
Find the number of units needed to cover fixed costs using price and variable cost per unit.
Estimate the number of bricks needed for a wall from wall area, brick dimensions, mortar joint and waste.
Count weekdays between two dates, excluding Saturdays and Sundays.
Calculate compound annual growth rate between a beginning value and ending value over a number of years.
Estimate daily calorie needs by multiplying estimated BMR by an activity factor.
Calculate CD maturity value and interest from deposit, APY or nominal rate, term and compounding.
Convert Celsius temperatures to Fahrenheit.
Calculate circumference and area from a circle radius.
Find the average, highest and lowest score from a list of class or assignment scores.
Convert centimeters to inches.
Calculate combinations nCr: the number of ways to choose r items from n when order does not matter.
Calculate commission and total pay from sales, commission rate and optional base pay.
Project how money grows when interest is added to the balance and earns interest over time.
Estimate concrete masonry units (CMU) needed for a wall from wall dimensions, block face size and waste.
Estimate cubic yards of concrete for a rectangular slab and add an optional waste allowance.
Calculate cone volume, slant height and total surface area from radius and vertical height.
Calculate conversion rate from conversions and total visitors, sessions, leads or clicks.
Convert common U.S. cooking volume measurements including teaspoons, tablespoons, cups, fluid ounces, pints, quarts, gallons, milliliters and liters.
Compare state price levels using BEA Regional Price Parities and estimate an equivalent spending amount.
Calculate cost per acquisition (CPA) from campaign spend and acquired customers or conversions.
Calculate cost per square foot or total project cost from area and total price.
Calculate how much time remains until a future date and time, or how much time has elapsed since a past target.
Calculate advertising cost per click (CPC) from total ad spend and clicks.
Calculate cost per thousand impressions (CPM) from ad spend and impressions.
Estimate how long a credit-card balance takes to pay off with a fixed monthly payment, assuming no new charges.
Calculate click-through rate (CTR) from clicks and impressions.
Calculate cubic feet and cubic yards from length, width and height measurements.
Convert rectangular dimensions in feet to cubic yards for soil, gravel, concrete and landscaping materials.
Convert US customary cups to milliliters.
Convert money between major currencies using the latest available reference exchange rate.
Calculate customer acquisition cost by dividing acquisition spending by new customers gained.
Estimate simple customer lifetime value (CLV) from average order value, purchase frequency, gross margin and customer lifespan.
Calculate the volume and total surface area of a right circular cylinder.
Convert digital storage between bytes, kilobytes, megabytes, gigabytes and terabytes using decimal units.
Add or subtract calendar days from a date to find an exact past or future date and weekday.
Find the weekday for any valid calendar date.
Count the number of calendar days between two dates.
Count calendar days from a starting date to a future or past target date.
Estimate payoff time and interest for a debt when you make a fixed monthly payment.
Calculate your debt-to-income ratio by comparing monthly debt payments with gross monthly income.
Convert decimal hours to hours and minutes.
Convert a terminating decimal to a reduced fraction and mixed number.
Estimate deck area and project cost from deck dimensions, cost per square foot and a contingency percentage.
Estimate deck surface area, board runs, linear feet and board count with waste.
Calculate density from mass and volume, and also report specific volume.
Calculate a sale price, amount saved and optional final price after sales tax.
Calculate straight-line distance between two points on a 2D coordinate plane.
Estimate straight-line distance between the geographic centers of two U.S. ZIP codes.
Estimate drywall sheet count from wall dimensions, room count, sheet size and waste allowance.
Compare two locations, estimate their elevations, straight-line distance and average grade between them.
Convert energy between joules, kilojoules, calories, kilocalories, watt-hours and kilowatt-hours.
Round numbers to the nearest 1, 10, 100 or 1,000, estimate arithmetic, and compare the estimate with the exact answer.
Estimate battery energy added, wall energy required and EV charging cost.
Calculate a base raised to an exponent and see the reciprocal form for negative exponents.
Convert Fahrenheit temperatures to Celsius.
Estimate fence pickets from fence length, picket width and gap between pickets.
Find the score needed on a final exam to reach a desired overall course grade.
Estimate flooring area and purchase quantity with a waste allowance.
Add, subtract, multiply or divide two fractions and reduce the result to lowest terms.
Convert vehicle fuel economy between miles per gallon (U.S.) and liters per 100 kilometers.
Find the future value of a present amount after a chosen rate of return and time period.
Convert US liquid gallons to liters.
Estimate gallons used, fuel cost and fuel cost per mile from distance, MPG and gas price.
Find the greatest common factor (greatest common divisor) of two or more whole numbers.
Calculate an unweighted GPA from up to six course grades and credit hours on a standard 4.0 scale.
Calculate a current course percentage from points earned and points possible.
Estimate cubic yards and approximate tons of gravel from area and depth.
Estimate grout volume from tile size, joint width, joint depth and tiled area.
Convert an amount using an exchange rate from a selected historical date.
Estimate a home-price range from income, debt, down payment, mortgage rate and debt-to-income assumptions.
Convert an hourly wage to estimated weekly, monthly and annual gross pay.
Convert hours and minutes into decimal hours for timesheets and payroll calculations.
Find elapsed hours and minutes between two clock times, including overnight intervals.
Compare several common adult ideal-body-weight formulas based on sex and height.
Convert inches to centimeters.
Compare U.S. dollar purchasing power between years using annual-average CPI-U data.
Calculate inventory turnover and approximate days inventory on hand from cost of goods sold and average inventory.
Calculate investment gain, total return and annualized return from a beginning value, ending value and holding period.
Build a project price from labor, materials, subcontractors, overhead, profit markup and optional tax.
Convert kilograms to pounds.
Calculate kinetic energy from an object’s mass and velocity.
Calculate total lawn area from up to four rectangular sections and convert square feet to acres.
Find the least common multiple of two or more whole numbers.
Convert length between inches, feet, yards, miles, millimeters, centimeters, meters and kilometers.
Calculate the payment and total interest for a standard installment loan with equal monthly payments.
Convert a daily calorie target and macro percentages into grams of protein, carbohydrates and fat.
Calculate gross margin percentage and profit dollars from cost and selling price.
Calculate selling price and markup percentage from an item cost and desired markup.
Find the mean, median, mode and range of a list of numbers.
Find the midpoint between two points on a coordinate plane.
Calculate solution molarity from moles of solute and solution volume.
Calculate completed calendar months plus remaining days between two dates.
Calculate a fixed-rate monthly mortgage payment, total interest and total payments from loan amount, rate and term.
Compare extra monthly, annual and lump-sum principal payments to estimate payoff time and interest savings.
Calculate miles per gallon, gallons per 100 miles and liters per 100 kilometers.
Estimate cubic yards of mulch from bed area and desired depth.
Find the cumulative probability below, above or between values in a normal distribution.
Solve voltage, current, resistance and power from any two known electrical values.
Estimate one-repetition maximum (1RM) from a lifted weight and repetition count using common strength formulas.
Estimate weekly gross pay from regular hours, overtime hours, hourly rate and an overtime multiplier.
Estimate gallons of wall paint from room dimensions, wall height, coats and paint coverage.
Estimate paver count from project area, paver size and waste allowance.
Calculate a new salary or wage, dollar increase and approximate monthly increase from a percentage raise.
Estimate 2026 U.S. take-home pay using federal withholding, Social Security, Medicare and an optional state/local rate.
Calculate percentage increase or decrease from an original value to a new value.
Calculate symmetric percent difference between two values without treating either one as the original value.
Calculate percent error between an experimental or measured value and an accepted value.
Solve common percentage questions: find a percentage of a number, determine what percent one number is of another, and calculate a value from a known percentage.
Calculate permutations nPr: the number of ordered arrangements of r items chosen from n.
Estimate rectangular pool water volume in gallons from length, width and average depth.
Calculate population change, percent growth and annualized growth between two population counts.
Convert pounds to kilograms.
Discount a future amount back to its value today using a selected annual discount rate.
Convert pressure between psi, pascals, kilopascals, bar and atmospheres.
Break a positive whole number into its prime factors.
Calculate the probability of one event, its complement, and simple independent AND/OR combinations.
Calculate net profit, profit margin and revenue retained after expenses.
Solve a proportion of the form a/b = c/d when one of the four values is unknown.
Find the hypotenuse of a right triangle from the two perpendicular side lengths.
Solve a quadratic equation in the form ax² + bx + c = 0 and identify real or complex roots.
Generate one or more random numbers within a selected minimum and maximum range.
Simplify a ratio of two whole numbers to lowest terms.
Calculate area, perimeter and diagonal of a rectangle from length and width.
Estimate monthly savings, closing-cost break-even time and interest difference when refinancing a loan.
Compare estimated housing cost over a chosen period for renting versus buying a home.
Find the average needed on remaining coursework to reach a target overall grade.
Solve a right triangle from two side lengths and find the hypotenuse, angles, area and perimeter.
Estimate a road-trip budget including fuel, tolls, lodging, food and other costs.
Calculate return on ad spend from advertising-attributed revenue and ad cost.
Calculate return on investment from an initial cost and the amount received or current value.
Estimate roofing squares and bundles from roof area and waste percentage.
Calculate average running pace and speed from distance and elapsed time.
Estimate a cost-of-living-equivalent salary between two U.S. states using BEA Regional Price Parities.
Convert annual salary to an estimated hourly rate from weekly hours and weeks worked per year.
Calculate sales growth or decline from a prior-period sales amount to a current-period amount.
Estimate sales tax from a U.S. ZIP code using its state rate and 2026 statewide average local rate.
Calculate sales tax and the final purchase total from a pre-tax price and tax rate.
Estimate sand volume and approximate weight from project dimensions and material density.
Estimate the future value of savings with an initial balance, regular monthly contributions and compound interest.
Use common scientific functions including powers, roots, logarithms, exponentials and trigonometric functions.
Convert a number to normalized scientific notation and evaluate a coefficient times a power of ten.
Estimate siding square footage and squares from exterior wall dimensions, openings and waste.
Calculate interest earned or charged when interest is applied only to the original principal.
Find the slope of the line through two coordinate points.
Convert speed between miles per hour, kilometers per hour, meters per second and knots.
Solve for speed, distance or travel time when two of the three values are known.
Calculate the volume and surface area of a sphere from its radius.
Calculate rectangular area in square feet from length and width measurements in feet.
Calculate square roots and nth roots, including exact decimal results for positive and negative values when defined.
Estimate stair riser count, actual riser height and tread run from total rise and target riser height.
Calculate mean, variance and standard deviation for a sample or an entire population.
Estimate the monthly payment, total repayment and total interest on a fixed-rate student loan.
Estimate exercise heart-rate zones from age using a simple percentage of estimated maximum heart rate.
Estimate total daily energy expenditure (TDEE) from age, sex, height, weight and activity level using the Mifflin–St Jeor BMR equation.
Convert temperature between Fahrenheit, Celsius and Kelvin.
Convert correct answers and total questions into a test percentage.
Estimate the number of rectangular tiles needed for a floor or wall area, including waste.
Calculate weekly work hours and gross pay from daily clock-in, clock-out and unpaid break times.
Find elapsed time between a start time and end time, including overnight periods.
Convert a date and time between common world time zones using browser-supported IANA time zone rules.
Calculate a tip, total bill and per-person amount when splitting a restaurant or service bill.
Compare tire diameter, circumference, revolutions per mile and speedometer difference.
Estimate cubic yards of topsoil from area and desired depth.
Estimate a planning towing limit from GCWR, loaded vehicle weight and manufacturer tow rating.
Calculate triangle area using a base and perpendicular height.
Estimate total trip miles, fuel use and fuel cost for one-way or round-trip driving.
Estimate future vehicle value and depreciation using a constant annual depreciation rate.
Calculate volume for a rectangular prism, cylinder, sphere or cone.
Convert volume between U.S. gallons, quarts, pints, cups, fluid ounces, liters and milliliters.
Calculate waist-to-height ratio using waist circumference and height in the same units.
Calculate walking pace and speed from distance and elapsed time.
Estimate wallpaper rolls from wall area, roll coverage and waste allowance.
Create a simple daily hydration planning estimate from body weight, a chosen ounces-per-pound factor and optional exercise fluid.
Convert the calendar-day difference between two dates into weeks and remaining days.
Convert weight and mass between ounces, pounds, stones, grams, kilograms and metric tonnes.
Estimate GPA when honors or AP/IB courses receive extra grade-point weight.
Calculate a weighted course average from four category scores and weights.
Calculate paid work hours from start time, end time and an unpaid break.
Calculate a z-score from a value, mean and standard deviation.
Calculate a radius around a U.S. ZIP code and identify nearby postal places returned by the ZIP data service.
Find the county associated with the geographic center of a U.S. ZIP code.
Calculate triangle perimeter from three side lengths and validate the triangle.
Browse the first two roadmap passes as tightly connected topical clusters.
10 core calculators linked together for faster browsing and stronger topical coverage.
10 core calculators linked together for faster browsing and stronger topical coverage.
10 core calculators linked together for faster browsing and stronger topical coverage.
Materials and project-estimate calculators.
Fuel, tire, lease, towing and road-trip calculators.
Pay, pricing, profitability and sales calculators.