Useful calculators for money, math, dates, business, construction, school, health and conversions. Simple. Fast. Always free.
Start with the type of problem you want to solve.
Loans, savings, interest and everyday money decisions
Pricing, profitability, sales and business performance
Percentages, algebra, geometry and general math
Ages, date differences, workdays and time calculations
Materials, measurements and project estimates
Grades, GPA and classroom calculations
Common health and fitness estimates
Convert everyday measurements quickly
Quick access to frequently useful tools.
Estimate a fixed-rate mortgage payment, total interest and total of payments from the loan amount, interest rate and term.
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 age in years, months and days from a birth date to a selected date.
Calculate an unweighted GPA from up to six course grades and credit hours on a standard 4.0 scale.
Count weekdays between two dates, excluding Saturdays and Sundays.
Estimate cubic yards of concrete for a rectangular slab and add an optional waste allowance.
Calculate the payment and total interest for a standard installment loan with equal monthly payments.
Convert length between inches, feet, yards, miles, millimeters, centimeters, meters and kilometers.
New calculators we are expanding the site with.
Add daily work periods, subtract breaks, and estimate total weekly hours.
Estimate loan payments, total interest, and a complete month-by-month amortization schedule.
Calculate mean, variance, and population or sample standard deviation from a data set.
Estimate deck area and project cost from dimensions and cost per square foot.
ERICH Calculators is built as a practical reference: each tool has a dedicated page, a working calculator, the formula or method behind it, an example and links to related calculators. You can use the site without creating an account.
We are building this directory around common real-world questions—from loan payments and percentages to concrete volume, grades, dates and unit conversions. Bookmark the site and check back as the library grows.