What rMs_000 stated is incorrect. It is 3 weeks wage for every year worked, pro-rata for part years.

See article 54 of the labour law;

Article (54)

In addition to any sums to which the worker is entitled to upon the expiry of his service, the employer shall pay the end of service gratuity to the worker who has completed employment of one year or more. This gratuity shall be agreed upon by the two parties, provided that it is not less than a three-week wage for every year of employment. The worker shall be entitled to gratuity for the fractions of the year in proportion to the duration of employment.
The last basic wage shall be the base for the calculation of the gratuity.