Prenuptial Agreement Asset Division Calculator
Model how assets and debts might be divided in a divorce scenario, comparing a simple “no‑prenup” baseline to a custom prenup split. This is a planning tool, not legal advice.
Why People Consider Prenups
Prenuptial agreements are often misunderstood. In popular culture they can sound like a cynical bet against love. In real life, they are usually a pragmatic financial tool. A prenup is simply a contract that defines what happens to property and debt if a marriage ends by divorce or death. Couples consider them for many reasons: one partner owns a business, expects an inheritance, has children from a prior relationship, or is bringing substantially more assets into the marriage. Some couples use a prenup to avoid uncertainty; others use it to protect both partners from the financial chaos that a contested divorce can create.
Even if you never expect to use a prenup, thinking about how property division works is healthy. Every state has a default system for dividing property. If you do nothing, those default rules apply. A prenup lets you replace parts of those rules with terms you both agree to up front, when communication is calm and cooperative. This calculator helps you see the difference between those two paths in a simple, transparent way.
Community Property vs. Equitable Distribution
U.S. states generally follow one of two approaches:
- Community property states (such as California, Texas, and Arizona) treat most assets acquired during marriage as jointly owned 50/50. Separate property owned before marriage or received as a gift/inheritance typically stays separate, unless commingled.
- Equitable distribution states divide marital property in a way a court deems fair, which may be close to 50/50 but can differ based on income, caregiving, duration of marriage, and contributions.
This estimator uses a neutral baseline: it assumes marital property is split 50/50, and separate property stays with its original owner. That mirrors many outcomes and provides a consistent comparison to a prenup. If you live in an equitable distribution state and expect a different split, you can approximate it by adjusting the “no‑prenup marital split” field.
Key Terms Used Here
- Separate property. Assets owned by a spouse before marriage, or received individually as gifts or inheritances.
- Marital (community) property. Assets acquired or grown during marriage from joint effort.
- Commingling. Mixing separate and marital property in a way that can convert part of a separate asset into marital property (for example, using marital income to pay down a premarital mortgage).
- Marital contribution to separate property. Payments or investments made during marriage that increase the value of a separate asset.
The Simple Division Model
Let each spouse have separate property at marriage (SA and SB). During marriage, the couple accumulates marital assets (M) and marital debts (D). If marital property is split by a marital split percentage p to spouse A and (1−p) to spouse B, then the no‑prenup outcome is:
A prenup can change three things in a simple planning model: (1) the marital split percentage, (2) whether certain separate assets become partially marital due to commingling, and (3) whether one spouse receives a fixed “lump sum” or reimbursement for specific contributions. This calculator focuses on the first two because they are common and easy to model.
Worked Example
Suppose Alex and Jordan are marrying. Alex has $220,000 of separate assets (mostly retirement savings and a condo). Jordan has $60,000 of separate assets. Over 8 years, they accumulate $380,000 of marital assets and $40,000 of marital debt. They live in a community property state, so a baseline marital split is 50/50. They also use marital income to pay $50,000 toward Alex’s premarital condo mortgage, which they agree should be treated as a marital contribution that creates marital equity.
No prenup baseline. Net marital property is $380,000 − $40,000 = $340,000. Each spouse receives 50% = $170,000 of that. Alex receives $220,000 + $170,000 = $390,000. Jordan receives $60,000 + $170,000 = $230,000.
Prenup scenario. They agree that marital property will be split 60/40 in favor of Jordan to recognize caregiving and career sacrifice, and that the $50,000 mortgage paydown creates marital equity split on the same 60/40 basis. Net marital property is still $340,000. Jordan gets 60% = $204,000; Alex gets 40% = $136,000. Alex’s separate property remains $220,000. Alex total = $356,000. Jordan total = $264,000. The prenup narrows the gap and reflects their shared intent.
The specific numbers depend on the marriage’s reality, but the exercise shows why a prenup is a tool for aligning outcomes with values, not just protecting wealth.
Comparison Table: Common Prenup Structures
| Structure | What It Does | Who It Fits |
|---|---|---|
| Default marital split (50/50) | Mirrors state baseline | Couples wanting clarity without change |
| Unequal marital split (e.g., 60/40) | Pre‑sets a fairer outcome based on intent | One spouse expects career sacrifice or caregiving |
| Reimbursement / contribution clauses | Returns specific premarital or marital contributions | Business owners, homeowners, people with large student debt |
| Sunset clause | Prenup terms fade after years married | Couples wanting protection early, neutrality later |
Limitations and Assumptions
This calculator uses a simplified model so it is useful to a broad audience. It assumes:
- All separate property values are clearly identified and remain separate unless you enter marital contributions.
- Marital assets and debts are pooled and split by a single percentage.
- Appreciation, tax basis, and liquidity are ignored; values are in today’s dollars.
- Support obligations (alimony/child support) are not modeled. Many prenups can limit alimony but not child support.
Real divorces involve tracing, valuation disputes, business goodwill, and state‑specific rules. Use this tool to understand levers and talk productively, then consult a family‑law attorney to draft or review any agreement.