Calculators
Age, percentage, date and time difference calculators. Every tool operates locally in your browser memory without uploading your data or code to any server.
Available Calculators
Showing all 15 utilitiesCalculate percentages, increases and decreases.
Calculate exact age in years, months and days.
Find the number of days, months and years between two dates.
Calculate the duration between two times.
Live countdown to any date and time.
Count working days between two dates, excluding weekends and holidays.
Add or subtract a number of days from a date.
Add or subtract hours and minutes from a time.
Find the ISO week number for any date.
Find which day of the year a date falls on.
Check whether a year is a leap year.
Generate a printable calendar for any month.
Convert a date and time between timezones.
See the current time in multiple cities at once.
A stopwatch with lap timing.
Common Workflows & Practical Use Cases
How developers and teams use these calculators daily.
Percentage & Markup Math
Calculate percentage increase, decrease, discounts, and margins for everyday financial and analytical tasks.
Calendar & Business Days
Compute calendar intervals, elapsed days, working business days, and week numbers accurately.
Time Tracking & Countdowns
Track elapsed durations with lap stopwatches, countdown to upcoming events, and convert across world time zones.