Free Online Calculators

Age Calculator

Calculate your exact age in years, months, days, hours, and minutes from your date of birth. Find out how many days until your next birthday. Free online age calculator.

Aspect Ratio Calculator

Calculate missing dimensions from an aspect ratio, or find the ratio from a width and height. Supports any custom ratio and all standard screen sizes like 16:9, 4:3, 1:1, and more. Free, instant, browser-based.

Class Average Calculator

Free class average calculator for teachers. Paste a list of grades and instantly get the mean, median, highest, lowest, standard deviation, and letter grade distribution.

Cousin Relationship Calculator

Figure out exactly how you're related to a relative — first cousin, second cousin once removed, great-aunt, and more — based on how many generations each of you is from your shared ancestor.

Currency Converter

Convert between 30+ world currencies using real exchange-rate data from the European Central Bank. Free, fast, and runs in your browser.

Date Calculator

Add or subtract days, weeks, months, or years from any date to find a future or past date. What date is 90 days from today? What was 6 months ago? Free online date calculator.

Density Calculator

Calculate density, mass, or volume using the formula ρ = m/V. Choose from multiple units for each variable. Includes a reference table of common material densities. Free, instant, browser-based.

Extra Credit Calculator

Find out exactly how many extra credit points you need to hit your target grade, or see how bonus points affect your percentage average.

Final Grade Calculator

What do I need to make on my final to get an A this semester? This final grade calculator will tell you.

Force Calculator (F = ma)

Calculate force, mass, or acceleration using Newton's second law F = ma. Supports N, kN, lbf, dyne, kg, lb, m/s², ft/s², and g-force. Free physics calculator.

Half-Life Calculator

Calculate radioactive decay using the half-life formula. Solve for remaining quantity, elapsed time, half-life, or initial quantity. Supports seconds, minutes, hours, days, and years. Free, browser-based.

Hours Calculator

Calculate the hours and minutes between two times, or add and subtract multiple time durations. Supports 12-hour and 24-hour formats and spans past midnight. Free, instant, browser-based time calculator.

Ideal Gas Law Calculator

Solve the ideal gas law (PV = nRT) for any variable. Supports multiple units for pressure (atm, kPa, mmHg, bar, psi), volume (L, mL, m³), and temperature (K, °C, °F). Free, browser-based, instant results.

Kinetic Energy Calculator

Calculate kinetic energy (KE), mass, or velocity using KE = ½mv². Supports joules, kilojoules, calories, eV for energy; kg, g, lb for mass; m/s, km/h, mph, ft/s for velocity. Free, browser-based physics tool.

Letter Grade to GPA Converter

Convert instantly between letter grades, percentages, and GPA points on the 4.0 scale, including plus/minus grading and weighted AP/Honors points, with a full reference table.

Linear Grade Curve

This online grade curve calculator makes it a little easier to get your students' grades where you think they should be using a linear redistribution curve.

Molar Mass Calculator

Calculate the molar mass of any chemical compound by entering its formula. Handles parentheses, brackets, and all 118 elements. Shows a full element-by-element breakdown. Free, instant, browser-based.

Molarity Calculator

Calculate molarity (M), moles of solute, or volume of solution. Also includes a dilution calculator using M1V1 = M2V2. Free browser-based chemistry tool.

Online Easy Grader

Free online EZ grader for teachers. Enter the number of questions and max score to instantly generate a complete grade chart. Also includes a grade curve calculator to bump scores up.

Overtime Calculator

Calculate regular pay, overtime pay, and total weekly earnings using hourly rate, hours worked, and overtime multipliers.

Percentage Calculator

Calculate percentages instantly. Find what percent of a number is, what percentage one number is of another, and calculate percentage increase or decrease. Free online tool.

pH Calculator

Convert pH to hydrogen ion concentration [H⁺], hydroxide concentration [OH⁻], and pOH instantly. Or enter a concentration to get the pH. Includes an acid/base classification scale. Free, browser-based, no sign-up required.

Reading Time Calculator

Paste any text to instantly estimate reading time at your chosen reading speed. Shows word count, sentence count, and reading time in minutes. Free, instant, browser-based reading time estimator.

Semester Grade Tracker

Track your grades across all courses during the semester. Add assignments, see your running average per class, and check your projected GPA. Free, no sign-in needed.

Speed and Velocity Calculator

Calculate speed, distance, or time using speed = distance / time. Supports m/s, km/h, mph, ft/s, and knots. Free physics calculator, no signup.

Square Root Curve

Instantly curve grades with a square root (Texas) curve. See the formula, worked examples, a full 0-100 score chart, and FAQs. Free, no signup.

Stoichiometry Calculator

Calculate moles and grams of a product or reactant using stoichiometry. Enter the coefficients from a balanced chemical equation, the molar masses, and the known amount to find the unknown. Free, browser-based chemistry tool.

Temperature Converter

Instantly convert temperatures between Celsius, Fahrenheit, Kelvin, and Rankine. See all four scales at once with conversion formulas. Free, browser-based temperature converter.

Test Corrections Calculator

Give students partial credit for test corrections. Enter scores, pick a percentage returned (e.g. half points back), and get every corrected grade instantly.

Test Score Calculator

Instantly turn correct answers into a percentage and letter grade, or find the max questions you can miss and still hit your target grade.

Unit Converter

Convert between metric and imperial units of length, weight/mass, and volume instantly. Free, accurate, and runs entirely in your browser.

VLSM Calculator

Free VLSM calculator for network subnetting. Calculate optimal subnet allocation with variable length subnet masks. Get network address, CIDR, netmask, usable IP ranges, and broadcast addresses.

Wave Frequency Calculator

Calculate wave speed, frequency, or wavelength using v = fλ. Also finds period (T = 1/f). Supports m/s, km/s, Hz, kHz, MHz, m, nm, and more. Free browser-based physics tool.

Weighted Grade Calculator

Calculate final grades using weighted categories like homework, tests, and projects. Enter category weights and scores to instantly calculate a weighted final grade. Free for teachers and students.

Work Days Calculator

Count the number of working days between two dates, excluding weekends and optional public holidays. Free business day calculator for deadlines, contracts, and project planning.