4 FREE TOOLS
Calculators for percentages, dates and units
Choose a calculation that matches your question. Each tool shows the result beside its controls and explains its rules. Number calculations use a decimal point; date tools compare calendar dates rather than elapsed hours in your local time zone.
Choose a tool
Straightforward answers, with the calculation explained.
Percentage Calculator
Find a percentage, a share or a percentage change.
Open toolDate Difference
Find the number of calendar days between two dates.
Open toolUnit Converter
Convert common length, mass and temperature measurements.
Open toolDate Add & Subtract
Find the date a whole number of days or weeks before or after another.
Open toolChoose the calculation that fits
An amount, a share or a change?
Percentage Calculator has separate modes for a percentage of a number, a part’s share of a total and a change from an earlier value. Choose the mode before entering numbers. A share cannot divide by zero; percentage change needs a positive starting value. Displayed results are rounded.
How many days are between two dates?
Date Difference excludes the starting day: January 1 to January 2 is one day. Weekends and holidays count. It measures calendar days using UTC, so daylight saving time does not add or remove a day. It is not a business-day calculator; reverse the dates for a negative interval.
Which date comes before or after?
Date Add & Subtract moves a date by whole days or weeks. One week means seven calendar days, including weekends. Choose Add or Subtract rather than entering a negative count. Months, years and working-day schedules are outside this tool’s rules.
Convert a measurement
Unit Converter handles length, mass and temperature using fixed definitions. Select both units explicitly. It does not fetch currency rates or convert compound units. Temperature conversions include offsets as well as scaling, and values below absolute zero are rejected.