There's no math formula or easy way to figure this out. Basically, the judge takes a big picture look at your situation.There is no set formula for calculating spousal support, as it's determined on a case-by-case basis. All alimony in California is based on one spouse's need for support and the other spouse's ability to pay. Agreements must be fair and reasonable. Generally, spousal support is paid for half the length of the marriage if it was less than 10 years. The judge will not use a formula to figure out how much spousal or partner support to order at the end of your case. In this article we are going to discuss the calculation of temporary spousal support (also called alimony) in the middle of a divorce case. Complete all the fields below and then click the Calculate Spousal Support button. 2. Our calculator formula is based on the Santa Clara guideline.