There is no hard and fast rule to calculate the any kind of maintenance. You can bargain before the court on the basis of following grounds.
The factors that the court takes into consideration for permanent alimony/maintenance for the wife as as follows:
A) The status and position of the husband, his income, his assets and his lifestyle. The position and status have reference more to the financial than to the social position. Income and financial status are the most important factors while arriving at a justified amount to be awarded as alimony/maintenance.
B) The reasonable wants of the wife. Want is not confined to what is required for keeping the claimant wife alive and providing for food only. When a minor child is living with the mother, the necessities of the child are also considered. Much emphasis is given on the reliefs prayed for by the wife by taking into consideration the status and station in life of the parties, the duration of the marriage, support and education of children, the ability of the spouse to earn and their future prospects, as also their age, health, liabilities, liabilities of the husband and the reasonable wants of the wife.
C) The wife's own income or earnings. The court will not only take into account the position of the husband but also the position and situation of the wife. In case the wife is working and drawing a handsome salary, the Court will certainly take that into consideration along with the husband's income and then depending on the facts and circumstances of the case decide whether alimony/maintenance is to be awarded to the wife and if yes, then the amount she shall receive from the husband.
As discussed earlier, under the provisions of the Hindu Marriage Act, 1955, even a Hindu husband can claim alimony from his wife if he earns less than her or does not earn at all, though this is rare.
Usually, the husband is bound to maintain his wife till her lifetime.
However, if the wife remarries, the husband is absolved of his responsibility and can petition the court for orders to stop the alimony. Similarly, if there is a change in circumstances, that is, the husband is unable to maintain the wife due to a financial crisis or any other adverse situation and the wife is financially independent earning a decent salary, then the husband may petition to the court to address the changed circumstances. The the court may, taking into account the facts, evidences and circumstances prevailing at that point of time, modify, vary or rescind the order.
The discretion to award lump-sum alimony or a periodical amount vests with the court.
If the spouse paying alimony/maintenance earns more income after the award for permanent alimony/maintenance has been passed in the case then the wife receiving alimony/maintenance may make a petition addressing the court about the increase in the husband's income but she will have to prove her inability to maintain herself with the alimony already awarded by the court. The court may take into account the facts, evidences and circumstances prevailing at that point of time increase the alimony payable. However, just because his income goes up does not necessarily mean she will get more alimony.
In the future, if the person receiving alimony gets richer (creates/inherits more wealth) than the one paying, can the flow of alimony be reversed? This would again depend upon the facts and circumstances of the case. In case the wife receiving alimony inherits wealth and becomes richer, then the husband would have to make a miscellaneous petition to prove the same to the court. The court will again look into the merits of the case, that is, evidences produced to show that the wife is a richer lady than what she was when alimony was granted to her, inability of the husband to maintain the wife, and if he claims alimony to be awarded to him, that will again be decided by the court after looking into the parameters for awarding alimony/maintenance as discussed above.