Unit & date calculator
Convert length, weight, temperature, area, volume, speed, data and time — and work out the days between dates or add and subtract from a date. Fully offline.
Open Unit & date calculator →What is the unit & date calculator?
A free unit converter and date calculator that runs entirely in your browser. Convert between units of length, mass, temperature, area, volume, speed, digital storage and time, or work out the number of days between two dates and add or subtract days, weeks, months or years from a date. It works fully offline and remembers your last selections on your device.
How to use Unit & date calculator
- Pick a tab — Choose Units to convert measurements, or Dates to work with calendar dates.
- Choose a category — On the Units tab, select a category — length, mass/weight, temperature, area, volume, speed, digital storage or time.
- Enter a value and units — Type a number, then pick the From and To units. The result updates as you type, and the swap button flips the two units.
- Work with dates — On the Dates tab, set a start and end date to see the difference, or add and subtract an amount of days, weeks, months or years from a date.
Frequently asked questions
Which units can I convert?
Length, mass/weight, temperature, area, volume, speed, digital storage and time — each with a full table of common metric and imperial units.
Does it show the full breakdown between two dates?
Yes. The date difference is given as a years/months/days breakdown, plus the total number of weeks and business days.
Is my data sent anywhere?
No. Every conversion and date calculation happens in your browser, and your last tab and unit choices are saved only on your device.
Does it work offline?
Yes. The calculator has no dependencies and runs fully offline once the page has loaded.
Tips
- Use the swap button to flip the From and To units without re-typing the value.
- The all-units table shows your input converted into every unit in the category at once.
- For date maths, remember a month is treated as a calendar month, so adding one month can land on a different day count depending on the month.