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Euler’s Unit Converter

Simple and unobtrusive unit converter for most needs. It can be used as a regular app window but is also available as menu bar widget, and Today Notification Center widget *. Available in more than 20 languages.

  • Categories: Angle, Area, Crypto Currency, Currency, Data Units, Density, Energy, Force, Fuel Efficiency, Length, Mass, Power, Pressure, Speed, Temperature, Time, Timestamp, and Volume
  • Menu bar widget
  • Multiple converters are possible in the notification center (available until macOS Catalina 10.15)
  • Rates for more than 40 currencies **
  • Rates for 9 crypto currencies **
  • Settings (in menu bar) for: light and dark mode; keeping the window on top; thousands separator; decimal places
  • Share conversion via mail, messages etc.
  • Swapping of units
  • Localized to 23 languages: Arabic, Chinese (Simplified), Czech, Danish, Dutch, English, French, German, Greek, Hungarian, Korean, Indonesian, Italian, Japanese, Norwegian, Polish, Portuguese, Romanian, Russian, Spanish, Swedish, Thai, Turkish.

Requires macOS 10.13 (High Sierra) or higher. 

*  Today widgets with text input fields are not available anymore in macOS 11.0 (Big Sur) and will not show up. They are still available in macOS versions prior to 11.0.

** Data for currencies are provided by free data sources, which availability cannot be guaranteed.


Getting Started & Help

Add widget in notification center (pre macOS Big Sur only)

Open the notification center on your Mac and click on the “Edit” button at the bottom of the view. Then click on the green + button next to the Unit Converter. This is only available until macOS Catalina (10.15) and not in Big Sur (macOS 11) and later.

Add multiple converters in notification center (pre macOS Big Sur only)

Tap on the circled i button and then tap on the green + button (at the bottom of the list) to add more converters. Likewise converters can be deleted.

Change settings

In order to change the settings you have open the app (if you just use the notification center version, click on the settings icon in the Unit Converter). Go to the “View” menu item to see all settings.

What conversions are available in Euler’s Unit Converter?

Angle: Degree, Arc Minutes, Arc Seconds, Radians, Gradians, Revolutions

Area: Square Kilometer, Square Meter, Square Millimeter, Square Miles, Square Yards, Square Feet, Square Inches, Acres, Ares, Hectares

Crypto Currency: BTC, ETH, BNB, USDT, SOL, ADA, XRP, DOT, DOGE


Data Units: bit, kbit, Mbit, Gbit, byte, KB, MB, GB, TB, KiB, MiB, GiB

Density: Gram per Cubic Centimeter, Gram per Cubic Meter, Gram per Liter, Gram per Milliliter, Kilogram per Cubic Centimeter, Kilogram per Cubic Centimeter, Kilogram per Liter, Ounce per Cubic Foot, Ounce per Cubic Inch, Ounce per Gallon, Ounce per Gallon US, Pound per Cubic Foot, Pound per Cubic Inch, Pound per Gallon, Pound per Gallon US, Slug per Cubic Foot, Long Ton per Cubic Yard, Short Ton per Cubic Yard

Energy: Kilojoules, Kilocalories, Kilowatt Hours, BTUs, Foot Pounds, Newton Meter

Force: Newton, Dynes, Pond, Kilopond, Kilogram-Force

Fuel Efficiency: Liters per 100 Kilometers, Miles per Gallon, Miles per Imperial Gallon

Length: Nanometer, Micrometer, Millimeter, Centimeter, Meters, Kilometers, Inches, Feet, Yards, Miles, Nautical Miles, Light Years, Fathoms, Furlongs, Astronomical Units, Parsecs, Pixel, Points, Pica, Rem

Mass: Kilograms, Grams, Ounces, Pounds, Stones, Metric Tons, Short Tons, Carats, Ounces Troy, Slugs

Power: Watts, Kilowatts, Foot Pound Force Min, Foot Pound Force Sec, Metric Horsepower, Horsepower

Pressure: Newtons Per Meter Squared (Pascal), Kilopascals, Hectopascals, Inches of Mercury, Bars, Millibars, Millimeters of Mercury, Pounds per Square Inch

Speed: Meters per Second, Feet per Second, Kilometers per Hour, Miles per Hour, Knots, Speed of Light

Temperature: Celsius, Fahrenheit, Kelvin

Time: Years, Weeks, Days, Hours, Minutes, Seconds, Milliseconds, Microseconds, Nanoseconds

Timestamp: Unix, ISO 8601, RFC 2822, SQL, Core Data

Volume: Cubic Meter, Cubic Feet, Liters, Milliliters, Gallons, FluidDrams, Fluid Ounces, Pints, Quarts, Cups, Tablespoon, Teaspoon

Frequently Asked Questions

Why is the widget not available on macOS 11 (Big Sur) anymore?
Apple decided to remove support to prior macOS 11 widgets entirely. The new widget system does not allow text fields anymore (simply buttons are possible), which makes it useless for this app. They are still available in versions prior to macOS version 11. Since Euler’s Unit Converter version 2.0 a menu bar widget has been added to compensate for this issue.

How often are the currencies updated?
Currencies are provided by Fixer and FloatRates, and updated once a day. Crypto currencies are provided by CoinCap and updated every 10 minutes.

Why the name Euler?
Leonhard Euler (1707 – 1783) was a Swiss mathematician born in Basel, which is also the hometown of the developers.

Version History

V2.2.5 – 2023-07-19

  • Minor internal improvements

V2.2.4 – 1st January 2023

  • Precision bug fixing (temperature conversion)nometer and micrometer to “Length”

V2.2.3 – 30th November 2022

  • Improved “Menubar Startup”
  • Improved support for macOS 13 (Ventura)

V2.2.2 – 1st November 2022

  • Added nanometer and micrometer to “Length”
  • Bug fixing

V2.2.1 – 24th October 2022

  • Added input of fractions when using inches in “Length” (e.g., 1/8)
  • Internal optimizations
  • Requires min. macOS 10.13

V2.2 – 1st June 2022

  • New category: Force

V2.1 – 30th December 2021

  • New category: Crypto Currency
  • Improved formatting of small fraction numbers

V2.0.5 – 28th October 2021

  • Added rem unit to length category
  • Minor internal improvements
  • Optimized for macOS 12 (Monterey)

V2.0.4 – 4th September 2021

  • Added currency: Icelandic króna (ISK)
  • Improved Pica formatting (e.g., 2p3)
  • Minor internal improvements

V2.0.3 – 15th May 2021

  • Added to category Energy: Newton meter
  • Added currency: Malaysian Ringgit (MYR)

V2.0.2 – 20th February 2021

  • Added new category: density
  • Improved handling of preferences changes

V2.0.1 – 19th January 2021

  • Added currency: Uruguayan Peso
  • Fixed currency data update in menu bar widget
  • Minor bug fixing

V2.0 – 1st December 2020

  • Added menu bar app (compatible with macOS 11 Big Sur as previous today widgets are not available anymore); use option in preferences to enable/disable
  • Minor layout optimizations
  • Support Apple Silicon

V1.10 – 8th October 2020

  • The last selections for each category in app/widget are now preserved
  • Added preferences menu
  • Added to length category: Pica

V1.9.5 – 2nd April 2020

  • Added to timestamp category: Core Data
  • Increased window size
  • Minor bug fixes

V1.9.4 – 1st March 2020

  • Added to currency category: KWD
  • Added to speed category: feet per second

V1.9.3 – 20th December 2019

  • Added to currency category: UAH
  • Fixed issue to keep unit settings when selecting same category (widget only)

V1.9.2 – 22nd October 2019

  • Added to currency category: PKR, NGN
  • Added to length category: pixel, points

V1.9.1 – 6th October 2019

  • Fixed 24hr bug in ISO 8601 conversions (timestamps category)

V1.9 – 12th September 2019

  • Added new category “Timestamp” (converts between unix, ISO 8601, RFC 2822, and SQL formats)
  • Added currency: Georgian Lari (GEL)
  • Improved translations

V1.8.1 – 8th August 2019

  • List in widget can now be edited (to change order of converters)
  • Improved darkmode support
  • Improved touchbar support

V1.8 – 22nd July 2019

  • Widget now supports multiple parallel conversions
  • Added currency SCR, length units

V1.7 – 25th February 2019

  • Added currencies CRC, JMD, PEN
  • Fixed service for alternative currency source

V1.6 – 7th October 2018

  • Added possibility to swap units for even easier conversions
  • Fixed some layout issues

V1.5 – 20th September 2018

  • Support for macOS Dark Mode
  • Added currency: Ghanaian Cedi

V1.4.2 – 29th June 2018

  • Added “Data Units” category
  • Added to category “Volume”: Imperial Gallons

V1.4.1 – 4th April 2018

  • Added currency: New Taiwan Dollar

V1.4 – 31th January 2018

  • Added “Time” category

V1.3 – 26th April 2017

  • Added additional currency source with AED, CLP, QAR, SAR
  • Increased country flags size

V1.2 – 7th April 2017

  • Added localizations for: Indonesian, Romanian
  • Add touch bar support for settings
  • Fixed currency loading timeout

V1.1 – 25th March 2017

  • Added localizations for: Arabic, Chinese (Simplified), Czech, Danish, Dutch, Greek, Hungarian, Korean, Polish, Russian, Thai, Turkish

V1.0 – 19th March 2017

  • Initial Version