Calculator
Free online calculators for everyday and work needs including date calculator, percentage calculator, and ratio calculator.
Choose the right calculator before you compare results
The calculator category brings together everyday math, date, ratio, finance, health, and utility calculations that are easier to check in a focused tool than in a spreadsheet. Most tools are built for quick input changes, readable result cards, and enough detail to understand where the number came from.
Start with the calculator that matches your question, review the breakdown, then move to related converter, finance, health, or life tools when the next condition matters. Stable links on the category page make it easier to follow that path without hunting through unrelated pages.
52 tools
Common uses
- Check dates, percentages, ratios, and repeated everyday numbers.
- Estimate costs, fees, taxes, or time before making a decision.
- Compare scenarios by changing one input at a time.
- Move from a broad calculation to a more specific related tool.
Quick checks
Can I use the result as an official document?
No. These tools are for estimates and cross-checks. For tax, finance, medical, or legal decisions, confirm the official rule and your own conditions.
Which calculator should I open first?
Use a broad date, ratio, or unit calculator to shape the question, then open the more specific category tool for the final details.
Will the mobile result match desktop?
Yes. The calculation logic is the same; mobile only changes the reading order and layout.
Tools
52 toolsAge Calculator
Calculate your exact age in years, months, and days. Discover your zodiac sign, Chinese zodiac,...
Average Calculator
Paste numbers to calculate the arithmetic mean, median, sum, minimum, maximum, and range. Useful for...
Biorhythm Calculator
Enter your birth date to visualize your physical, emotional, and intellectual biorhythm cycles. Track daily...
Biorhythm Compatibility Calculator
Compare two birth dates across physical, emotional, and intellectual biorhythm cycles to find better dates...
Birthday Weekday Calculator
Check your birth weekday, Chinese zodiac, zodiac sign, next birthday weekday, and time lived so...
Camera Exposure Value (EV) Calculator
Enter any two values among aperture, shutter speed, and EV to calculate the third at...
Circle Calculator
Solve the rest of a circle from radius, diameter, circumference, or area, then review the...
Coefficient of Variation (CV) Calculator
Enter a number list or a mean and standard deviation to calculate sample or population...
Confidence Interval Calculator
Review t-based mean and Wilson proportion confidence intervals from a sample mean or proportion, with...
Date Calculator
Add or subtract days from a start date to find the date before or after...
Date Countdown Calculator
Calculate D-Day until your target date with real-time countdown and auto-save.
Date Difference Calculator
Calculate duration between two dates in years, months, weeks, and days with weekday/weekend breakdown.
Days Lived Calculator
Enter a birth date to see which day of life today is, plus age, total...
Days Remaining This Year
Calculate how many days remain until the end of the year in real-time. Track your...
Density Calculator
Enter any two of mass, volume, and density to solve the third value, then compare...
Discount Calculator
Calculate the final paid amount, total savings, and original subtotal from list price, discount rate,...
Factor Calculator
Enter a positive integer to view the prime factorization, full factor list, factor count and...
Factorial Calculator
Calculate exact factorials from 0! to 5,000! and review the digit count, trailing zeros, expansion,...
Fixed ISO Exposure Calculator
Use a fixed ISO and a reference aperture/shutter pair to calculate the matching shutter or...
FPE Calculator
Calculate foot-pounds of energy (FPE) from grain weight and fps. Instantly view Joules, m/s conversion,...
Fraction Calculator
Free online fraction calculator for two fractions with simplified answers, mixed numbers, decimal approximations, and...
Goal Achievement Rate Calculator
Enter a goal value and current progress to review the current achievement rate, remaining amount,...
Gravel Calculator
Enter area, depth, density, and extra allowance to estimate gravel order volume, weight, bag count,...
Horsepower Calculator
Enter torque and RPM to calculate hp, PS, and kW together, with normalized N·m torque...
Hydrogen Peroxide Concentration Calculator
Work out hydrogen peroxide stock volume, water amount, and dilution factor from the stock concentration,...
Molarity Calculator
Calculate moles, molarity (M), mM, and required mass for standard volumes from solute mass, molar...
Molecular Weight Calculator
Calculate molecular weight (molar mass) from a chemical formula with element contribution, total atoms, hydrate...
p-value Calculator
A calculator that uses a Z or t statistic, test direction, degrees of freedom, and...
Pay Raise Calculator
Check new salary, raise amount, monthly change, target gap, and future projection in USD from...
Percent Calculator
Calculate various percentages easily. Includes basic percent, ratio, change rate, discount, and reverse calculation with...
Percent Error Calculator
Enter a reference value and a measured value to review percent error, absolute error, signed...
Percentage Change Calculator
See percentage change, raw difference, a base-100 index, and the rate needed to recover the...
Proportion Calculator
Free proportion calculator for solving proportions, rule of three, proportional distribution, inverse proportion, and chain...
PSI to GPM Calculator
Enter pressure (PSI) and a US K-factor to estimate flow in GPM, L/min, and L/s,...
Pythagorean Theorem Calculator
Enter any two known sides of a right triangle to solve the missing side, verify...
Right Triangle Calculator
Calculate the base, height, hypotenuse, acute angles, area, perimeter, and trig ratios of a right...
Roofing Calculator
A roofing calculator tuned for square-foot and bundle-based estimates, with pitch, waste allowance, roofing squares,...
Root Calculator
Calculate square roots, cube roots, and other nth roots with powered verification, perfect-power checks, and...
Rounding Calculator
Round numbers by decimal places, nearest units, or significant figures and review the difference from...
RPM Calculator
Calculate RPM from diameter and surface or cutting speed, then convert RPM to Hz, rad/s,...
Slope Calculator
Enter two coordinates to calculate the slope, line equation, slope angle, midpoint, distance, rise, and...
Standard Deviation Calculator
Paste a list of numbers to calculate the sample standard deviation, population standard deviation, variance,...
Start and End Date Time Calculator
Calculate elapsed time between a start date/time and an end date/time in days, hours, minutes,...
Start and End Time Calculator
Calculate end times, reverse-calculate start times, and review break-adjusted work hours and overnight schedules on...
Start Date/Time + Duration Calculator
Add days, hours, minutes, and seconds to a start date and time to calculate the...
Surface Area Calculator
Enter dimensions for a cube, rectangular prism, cylinder, sphere, or cone to calculate total surface...
Travel Distance Calculator
Enter travel time and average speed to calculate distance in miles, feet, kilometers, and nautical...
Travel Time Calculator
Enter distance and average speed to calculate travel time, total time with a buffer, total...
Voltage Drop Calculator
Calculate voltage drop, receiving voltage, and wire loss for single-phase, three-phase, and DC circuits, then...
Weighted Average Calculator
Enter values and weights row by row to compare the weighted average, simple-average gap, weight...
Wh (Watt-hour) Calculator
Calculate Wh, kWh, and joules from power draw and runtime, convert battery mAh↔Wh, and estimate...
Z-Score Calculator
Calculate Z-score, cumulative percentile, distance from the mean, and reference score bands from a score,...