Moore Marsden Calculation California: How Premarital Home Equity Gets Split

When one spouse bought the family home before the marriage but community earnings (wages during the marriage) paid down the mortgage, the community acquires a proportional interest in the home's appreciation. This is the Moore-Marsden rule, named after two California appellate cases from the early 1980s — In re Marriage of Moore (1980) and In re Marriage of Marsden (1982).

The formula determines exactly how much of the home's value belongs to the community (split 50/50) and how much stays with the purchasing spouse as separate property.

The Formula

The Moore-Marsden calculation has three components:

Step 1: Calculate the community's ownership percentage

Community Percentage = Community Principal Payments ÷ Original Purchase Price

Only mortgage principal payments made with community funds during the marriage count. Interest payments, property taxes, insurance, and maintenance do not contribute to the community's equity stake.

Step 2: Calculate the community's share of appreciation

Community Share of Appreciation = Appreciation During Marriage × Community Percentage

Appreciation during the marriage is the difference between the home's value at the date of trial (or settlement) and its value at the date of marriage.

Step 3: Calculate total community interest

Total Community Interest = Community Principal Payments + Community Share of Appreciation

Each spouse is entitled to half of the total community interest. The remaining equity — including the down payment, pre-marriage principal payments, pre-marriage appreciation, and the separate property share of marital appreciation — belongs to the purchasing spouse.

A Worked Example

Sarah bought a house for $400,000 before the marriage with a $80,000 down payment. During 8 years of marriage, the couple paid $60,000 in mortgage principal using community funds. The home was worth $420,000 at the date of marriage and is worth $620,000 at the time of divorce.

• Community percentage: $60,000 ÷ $400,000 = 15%
• Appreciation during marriage: $620,000 − $420,000 = $200,000
• Community share of appreciation: $200,000 × 15% = $30,000
• Total community interest: $60,000 + $30,000 = $90,000
• Each spouse's share of the community interest: $45,000

Sarah keeps her separate property interest (the down payment, pre-marriage principal, pre-marriage appreciation, and 85% of the marital appreciation) and owes her spouse $45,000 as their half of the community interest.

Common Complications

Refinancing during the marriage does not change the home's character — it is still separate property. But a cash-out refinance where community funds pay the new, larger mortgage changes the principal reduction numbers. If the non-owning spouse was added to the title during the refinance, a transmutation analysis under Family Code Section 852 may also apply.

Home improvements paid with community funds do not factor into the standard Moore-Marsden formula. However, the community may have a separate reimbursement claim under Family Code Section 2640 for capital improvements that increased the property's value.

Post-separation payments are handled differently. If one spouse uses post-separation separate income to pay the mortgage, they may be entitled to Epstein credits — reimbursement of 50% of those payments from the other spouse.

What Documents You Need

To run the calculation accurately, you need:

• The original purchase price and closing statement
• The mortgage amortization schedule showing principal vs. interest breakdown by month
• An appraisal or comparable market analysis at the date of marriage (if the home was purchased well before the marriage)
• A current appraisal or agreed fair market value

The California Divorce Financial Split Guide includes a Moore-Marsden calculator worksheet that walks through each step with space for your specific numbers, plus guidance on handling refinances and mixed-source payments.

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