If your Basic (+DA) is 1000/-, assuming you have completed one year of service, then it is 12000/- x 8.33% (minimum) = 1000/-. If you have worked less than that period, calculate your basic x that many number of months in service x 8.33%. The company can declare a bonus of up to 20% as well, then the calculation will be that way.
Please note, some companies are very good. They do not involve any calculation, and management decides on a specific amount. For those with the company for over a year, this much, less than a year, this much, less than x months = no bonus, etc. As far as the bonus is concerned, it all depends on company policy.
Bonus Act and Exemptions
The Bonus Act clearly states an 8.33% minimum bonus even for a loss-making company. Here again, I forgot to mention a very important point - if the company/organization is formed & running for less than 5 years, such companies/organizations need not pay a bonus as they are exempted for the first 5 years of incorporation.
Here again, some companies are extremely nice to declare "Ex gratia" (instead of a bonus) if they are doing well.
Regards,
Sundararaman