How to Track the Value of a Property Portfolio Without Guesswork

The short answer

You do not need an estate agent's opinion to keep a property portfolio valued. The defensible way is to start from what you actually paid, re-index it to today using the official house-price index for that market, add the value your renovations created, then subtract what still stands between you and the cash: mortgage balance, taxes, and selling costs.

That gives you a repeatable, auditable equity figure that updates as the index moves — instead of a number you invent once and never revisit.

The method, step by step

1. 1

   Start from the purchase price

   Record what you actually paid and the year you bought. This is the anchor everything else adjusts from.

2. 2

   Re-index with an official house-price index

   Apply the change in the official index for that country or region between your purchase year and today. Public indices (such as OECD house-price data) reflect the whole market, not one agent's guess.

3. 3

   Add renovation uplift

   Capital improvements can raise value beyond the index. Add the value your work created — kept separate so the estimate stays auditable.

4. 4

   Subtract what you still owe and would pay to sell

   Deduct the outstanding mortgage, plus transaction taxes and selling costs, to move from gross value to real equity.

A worked example

Take an apartment bought in Paris in 2019 for €985,000, renovated since, with the official index up over the period:

Doing it automatically

Track your wealth applies this method for you across 21 markets — France, the US, the UK, Canada, Australia, and the Gulf among them — re-indexing from official house-price data in each property's local currency, then rolling equity into your overall net worth.