Co-Owner Buyout Calculator: Buy Someone Out of a House

Work out what it costs to buy someone out of a house — or what your own share is worth when you exit.

To calculate buying someone out of a house, take the property's current market value, subtract the outstanding mortgage to get the net equity, then multiply that equity by the leaving owner's ownership percentage.

Last updated August 2026

When one co-owner wants out, the others often buy their share. This calculator estimates that buyout from three numbers: what the property is worth now, what is still owed on the mortgage, and the exiting owner's ownership percentage. It is the same net-equity approach Laddered uses when co-owners run an exit.

The result is a starting figure for a fair conversation — the actual price also depends on costs, taxes and what your co-ownership agreement says.

How this calculator works

  • First it works out the property's net equity: current value minus the outstanding mortgage (and any unpaid shared costs, plus or minus adjustments you enter).
  • Then it multiplies that equity by the exiting owner's share. Buyout = net equity times ownership %.
  • If the mortgage is larger than the value, equity is negative — the property is underwater — and the calculator says so rather than showing a meaningless negative payout. In that situation the departing owner may owe money toward the shortfall rather than receive a payout.

Worked examples: 50/50 and 70/30

A property is worth $500,000 with $300,000 still owing, so net equity is $200,000. A co-owner with a 40% share would be bought out for 40% of $200,000 = $80,000. In a straight 50/50 split, buying the other person out of that house costs $100,000.

Unequal shares work the same way. Say two friends own 70/30 because one put in the bigger deposit: on the same $200,000 of equity, buying out the 30% owner costs $60,000, and buying out the 70% owner costs $140,000. The percentage does the work — which is why co-owners should have their split recorded in writing before anyone wants to leave.

If the departing co-owner had also fronted unpaid repairs, you would add those back as an adjustment; if there are selling-style costs to account for, you would subtract them. To actually fund the payout, the remaining owner usually refinances the mortgage into their own name and borrows the buyout amount on top — so check your borrowing power covers the full new loan, not just the payout.

Australia and the United States

The math is the same wherever you buy. For country-specific tax and legal detail — stamp duty and CGT in Australia, closing costs and capital gains in the US — read the guide for Australia or the United States.

Good to know

  • Estimates equity times share; it does not include agent, legal or refinancing fees unless you add them as an adjustment.
  • Does not calculate stamp duty, CGT or US capital gains tax owed.
  • Educational estimate — not legal, tax or financial advice.

Frequently asked questions

How do I calculate buying someone out of a house?

Take the property's current market value, subtract the remaining mortgage balance to get the net equity, then multiply the equity by the other person's ownership percentage. A $500,000 house with $300,000 owing has $200,000 of equity, so buying out a half owner costs $100,000. This calculator does the math and lets you add costs or adjustments.

What if we own the house 70/30 instead of 50/50?

Use the actual percentages: the buyout is net equity times the departing owner's share, so a 30% owner of $200,000 equity is bought out for $60,000. If you never agreed shares in writing, the title (or in some cases each person's contributions) determines them — agree the number first, then run the calculation.

Where does the money to buy someone out come from?

Usually a refinance: the remaining owner takes a new loan in their own name big enough to pay out the old mortgage plus the buyout amount. You need to qualify for that loan on your income alone, which is where buyouts most often stall — check your borrowing power before agreeing a figure.

What if we owe more than the property is worth?

That is negative equity. The calculator flags it and, rather than a payout, the exiting owner may need to contribute toward the shortfall. Get advice before acting.

Does a buyout trigger tax or duty?

Often, and it differs by country. In Australia the buyer may pay transfer (stamp) duty on the share acquired and the seller may face capital gains tax; in the US the seller may owe capital gains tax, with the Section 121 exclusion possibly applying. Confirm with a professional — see the Australian and US guides on this page.

How is the property valued for a buyout?

Usually by a professional appraisal or an agreed valuation. This tool uses the value you enter, so use a realistic market figure.

Do we have to refinance to buy someone out?

Generally yes. To release the departing owner from the mortgage, the remaining owners usually refinance the loan into their names, subject to the lender's approval.