How to calculate ownership shares when buying a home together
6 min read
The ownership share should follow what each of you actually finances: set it from your equity contributions alone, or from total financing (equity plus loan shares) — and document the choice at the purchase, not years later.
In short
- The ownership share is a decision, not a default — 50/50 fits few couples with unequal contributions.
- Two common models: split by equity only, or by total financing (equity plus loan shares).
- The shares should be documented at the purchase, in the title documents and in a written agreement.
- Ongoing contributions after the purchase can shift the picture — log them as they happen.
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Start with the financing, not the feeling
Ownership shares are easiest to get right if you ignore what feels fair for a moment and look at who pays for what. The purchase has two funding sources: the equity you each bring, and the loan you take on. Your shares can be calculated from either one, or from both together.
There is no single correct formula. What matters is that you pick a model deliberately, agree on it, and write it down — because what is documented at the purchase is what counts later.
A worked example
Say the home costs 2,500,000. Partner A brings 400,000 in equity, partner B brings 100,000, and you take a joint loan of 2,000,000 that you each service equally.
If you split by equity only, the shares are 80/20 — A funded 80 percent of the equity. That is simple, but it ignores that B carries half the loan.
If you split by total financing, each of you counts their equity plus their loan share: A has 400,000 + 1,000,000 = 1,400,000, B has 100,000 + 1,000,000 = 1,100,000. The shares become 56/44. For most couples this model tracks reality better, because the loan commitment is real money too.
Why 50/50 rarely fits
Registering 50/50 is the path of least resistance, and it is exactly what many couples do. It works fine when contributions are genuinely equal. When they are not, it quietly transfers value from one partner to the other — often discovered only at a separation or a buyout, when it is too late to discuss calmly.
Choosing unequal shares is not a lack of trust. It is a precise description of what each of you put in, which protects both of you.
Document it at the purchase — and after
The shares should be visible in the title or deed documents where you buy, and mirrored in a written cohabitation agreement that explains how they were calculated. If the paperwork says 50/50 but you intended 56/44, the paperwork usually wins.
Life does not stop at the purchase. Renovations, extra repayments or one partner covering the costs during parental leave can all change what each of you has invested. Decide whether such contributions adjust the shares or are handled in the settlement — and keep a running record either way.
Next steps
Start with the numbers: run your actual equity and loan shares through the calculators in cohab and see what each model gives you. Then have the conversation, pick a model, and write it into your agreement with digital signatures so it actually exists.
Once the shares are set, log contributions as they happen. A settlement built on live numbers is a calculation; one built on memory is a negotiation.
Frequently asked questions
What if we borrow different amounts?
Then the total-financing model handles it naturally: each partner counts their own equity plus their own loan share. Just make sure the loan split is real — if you are jointly liable for the whole loan regardless, discuss what that means and write it down.
Can the ownership shares be changed later?
Yes, but it is a real transaction, not an edit. Changing registered shares may require new paperwork and can have tax or fee consequences depending on your country. Agree the new split in writing and take local advice before changing the title documents.
Does equity from an inheritance count the same?
From a financing perspective, yes — 100,000 from an inheritance funds the purchase exactly like 100,000 from savings. Some couples still treat inherited money as more personal and want it protected; that is a legitimate choice to make explicitly in the agreement.
What is the most common mistake couples make?
Registering 50/50 by default and never writing down how the shares were meant to work. The second most common is agreeing on unequal shares but leaving the title documents at 50/50. In both cases the paperwork, not the intention, decides.
How ownership shares are registered, changed and divided varies between countries, and cohabitants rarely have the same automatic rights as spouses. Document your own arrangement at the purchase and take local advice for your situation.
This guide is general information, not legal advice. Rules differ between countries — consult a local professional for your situation.
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