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How our calculators work and where the data comes from

Last updated 14 October 2026

Every result on this site comes from a published rule, a standard formula or an official data source. This page lists them, so you can check our work. Each calculator also shows its own source and the date we last checked it.

Work and pay (UAE and Saudi Arabia)

  • UAE gratuity: Article 51 of Federal Decree-Law No. 33 of 2021. 21 days of basic salary for each of the first five years and 30 days for each year after, with part years pro rata and a cap of two years' wage.
  • Saudi end of service: Articles 84 and 85 of the Saudi Labor Law. Half a month's wage for each of the first five years and a full month after, reduced on resignation to one third, two thirds or the full award by length of service.
  • UAE annual leave: Article 29 of Federal Decree-Law No. 33 of 2021.
  • These are estimates. Your employer or the labour ministry gives the official figure.

Tax and money

  • VAT: 5% in the UAE and Oman, 10% in Bahrain and 15% in Saudi Arabia, rounded to the smallest coin.
  • Loans: the standard reducing-balance instalment formula, with flat rates converted to the equivalent reducing rate.
  • Zakat: 2.5% of zakatable wealth once it reaches the nisab of 85 grams of gold or 595 grams of silver.

Live and dated data

  • Gold and silver: international spot price from Gold API, refreshed every hour and shown with its time. Gulf currencies use their official US dollar pegs; other currencies use the European Central Bank reference rates.
  • Weather: MET Norway forecasts (CC BY 4.0), refreshed about every 30 minutes.
  • Fuel prices: official monthly or weekly prices from each country's publisher, such as the UAE Fuel Price Committee, Saudi Aramco and the European Commission, updated by hand every month and never called live.
  • If a feed fails we show the last known value and label it.

Dates, direction and health

  • Hijri dates: the Umm al-Qura calendar of Saudi Arabia. Ramadan and Eid dates are always marked as expected, because moon sighting decides.
  • Qibla: the great-circle bearing from your location to the Kaaba in Makkah.
  • BMI: the World Health Organization categories for adults.
  • Ideal weight: the WHO BMI range plus the Devine, Robinson, Miller and Hamwi formulas.
  • Pregnancy due date: Naegele's rule, 280 days from the first day of the last period, adjusted for cycle length. Health tools are for information, not diagnosis.

Found a mistake?

Laws and rates change. If a result looks wrong, email services@zkdigitals.com with the tool, what you entered and what you expected. We will check it against the source and correct the page with a new date.