What a property division actually decides
Dividing property in a divorce is three decisions in order, and only the third is arithmetic. First, which assets are marital and which are separate. Second, what percentage of the marital estate each party receives. Third, how to hand out specific assets so that each party ends up with their percentage — and since houses, pensions and businesses cannot be cut in half, the answer is almost always an equalising payment from whoever received more to whoever received less.
The first decision is legal. Property acquired during the marriage is presumptively marital; property owned before the marriage, or received during it by inheritance or gift, is presumptively separate. That presumption is defeated by commingling, by transmutation into joint title, and in many states by any increase in value attributable to marital effort. A pre-marital business that grew because a spouse worked in it for fifteen years is rarely still wholly separate.
The second decision depends on where you are. Nine community property states start from an equal division of community property. The rest apply equitable distribution, which means fair rather than equal: courts weigh the length of the marriage, each party's contributions including homemaking, earning capacity, health, and the needs of a custodial parent. Equitable-distribution outcomes cluster near an even split in long marriages and diverge from it in short ones.
Only the third decision is what this calculator does, and it does it precisely.
The formula, and why after-tax value matters
Net the estate first: marital assets minus marital debts. Debt is part of the estate, not a footnote to it, and a settlement that divides assets evenly while loading the debts onto one side is not an even settlement. Multiply the net estate by each party's share to get their target.
Then value what each party is actually receiving, net of the debts they are assuming. Subtract that from their target. The difference is the equalising payment: positive means they are short and are owed money, negative means they hold more than their share and owe it.
The tax adjustment is where settlements most often go quietly wrong. A dollar in a traditional 401(k) is not a dollar. It is a dollar minus the income tax that will be paid on withdrawal, and if the holder is in a 22% bracket it is worth about 78 cents. A dollar of appreciated stock carries a latent capital gains liability. A dollar in a Roth account or a bank account carries neither. Splitting a $400,000 estate as $200,000 of 401(k) against $200,000 of cash looks even and is not: on the default figures here, a $22,000 embedded tax on Party A's side shifts $11,000 of the equalising payment, because the estate shrinks by the full $22,000 while only Party A's side of the ledger absorbs it.
This is why the after-tax switch exists, and why it should usually be on. The counter-argument is that the tax is speculative — the rate is unknown, the timing is unknown, and a Roth conversion or a low-income year can change it. That argument has force. It has less force than pretending the tax is zero.
Worked example: a $620,000 estate with $145,000 of debt
The marriage holds $620,000 of marital assets and $145,000 of marital debt. Party A keeps the house and their retirement account, worth $400,000 between them, and assumes $95,000 of the debt including the mortgage. Party A's retirement account carries $22,000 of deferred income tax; Party B's share is cash and carries none. Party A also brought $80,000 of traceable separate property into the marriage and Party B brought $25,000. The split is even.
- Net the estate. $620,000 − $145,000 = $475,000, less $22,000 of embedded tax = $453,000.
- Target shares. 50% each: $226,500 to Party A, $226,500 to Party B.
- Party A's net allocation. $400,000 of assets − $95,000 of debt − $22,000 of tax = $283,000.
- Party B's net allocation. $220,000 of assets − $50,000 of debt = $170,000.
- Equalising payment. $226,500 − $283,000 = −$56,500, so Party A pays Party B $56,500.
- Check it. Party A finishes with $283,000 − $56,500 = $226,500; Party B with $170,000 + $56,500 = $226,500. Both hit target.
- Add separate property. Party A ends at $306,500 and Party B at $251,500. The difference between them is exactly the $55,000 gap in separate property they each brought in, which the division never touched.
How to read the result
Start with the sign, then ask whether the payment can actually be made. An equalising payment is only useful if the paying party has liquid assets or borrowing capacity to fund it. Where they do not, the usual fixes are to reallocate assets so the gap narrows, to secure the payment against real property with a note and a deed of trust, or to pay it in instalments with interest. A promise to pay $56,500 over five years is worth less than $56,500 today, so if you take instalments, price them: run the schedule through a payment calculator and set a rate rather than agreeing to an interest-free note.
Then test the split sensitivity. The chart on this page shows the equalising payment across a range of split percentages, and the slope is the point: on a $453,000 estate, every percentage point of the split is worth $4,530. Arguments about whether a settlement should be 50/50 or 55/45 are arguments about five percentage points, which here is $22,650 — usually far more than the cost of getting the valuations right, which is where the same effort would be better spent.
Finally, check what the totals do and do not include. Separate property inflates a party's final total without having been divided, so the two total figures are not a fairness test. Future income is excluded entirely, and it is frequently the largest asset in the marriage: a spouse who left the workforce receives half the assets and a fraction of the earning capacity. That is what spousal support is for, and it is calculated separately.
What a dollar of each asset type is really worth
| Asset | Tax on realisation | After-tax value |
|---|---|---|
| Cash or checking | $0 | $100,000 |
| Roth IRA (qualified) | $0 | $100,000 |
| Traditional 401(k) or IRA | 22% of $100,000 = $22,000 | $78,000 |
| Stock with a $40,000 basis | 15% of $60,000 = $9,000 | $91,000 |
| Stock with a $95,000 basis | 15% of $5,000 = $750 | $99,250 |
Illustrative rates only; your bracket and holding period decide the real figures, and state income tax is not included. The point is the ordering, which holds at any rate: deferred accounts are worth least per nominal dollar and Roth and cash worth most.
Where property divisions go wrong
- Dividing at face value. Matching a 401(k) against a savings account dollar for dollar hands one party a silent tax bill. Use the after-tax switch.
- Forgetting the debts. An even asset split with an uneven debt split is an uneven settlement, and the mortgage is usually the largest item.
- Valuing a business by rule of thumb. Closely held businesses need a valuation, and the standard of value used matters: fair market value and fair value can differ substantially on the same company.
- Treating a pension as its account balance. A defined benefit plan has no balance. Its marital share is found with a coverture fraction, not by looking at a statement.
- Assuming separate property stayed separate. Depositing an inheritance into a joint account, or using it for a down payment on a jointly titled house, commonly converts it into marital property.
- Ignoring the transaction costs of the assets you keep. A house costs 6% to 8% of value to sell; a brokerage account costs almost nothing. Two assets carried at the same value are not equally liquid.
The other calculations a settlement needs
Property division is one of four numbers in a divorce, and they interact. If the house is the largest marital asset, the divorce house buyout calculator tells you whether one party can actually keep it, which often decides the allocation before any fairness argument is heard. If there is a defined benefit pension, its marital share comes from the QDRO coverture fraction calculator and needs a qualified domestic relations order to implement — a settlement agreement alone does not move retirement money.
Income runs on its own track: the child support estimate calculator and the alimony and spousal support calculator are not offsets against property, and courts generally resist trading one for the other because support is modifiable and property division is not. That difference is worth understanding before you negotiate: a property award is final, while a support order can be revisited if circumstances change.
For the tax side, the capital gains tax calculator gives you a defensible embedded-tax figure for appreciated holdings, and the home sale capital gains tax calculator handles the residence exclusion, which is $250,000 per person and therefore worth twice as much to a couple filing jointly before the divorce is final as to a single filer afterwards. That timing point alone has been worth six figures in some settlements.
Marital or separate is a legal question
This calculator takes your classification as given. It cannot tell you whether the inheritance that funded the kitchen renovation is still separate, whether the increase in value of a pre-marital business is marital, or whether your state applies the source-of-funds rule. Those questions decide the size of the estate before any percentage is applied, and they are worth professional advice precisely because they are worth more than the split percentage most people spend their energy arguing about.