About our value estimates
What is the Zoopla Estimate?
The Zoopla Estimate is our assessment of the market value of a home on any given day, calculated using a proprietary algorithm (secret formula) that continuously analyses millions of data points relating to property sales and home characteristics throughout the UK. Our estimates are constantly refined, using the most recent data available and a variety of methodologies, in order to provide the most current information on any home.
However, they are not formal valuations and cannot be used as such. They simply provide a useful start point for researching the likely value of a home and should be supplemented with additional research and professional advice.
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We not only provide current value estimates, but also project Zoopla Estimates back in time, which allows you to see the Value change for a property up to the current date.
How do you calculate a Zoopla Estimate?
The Zoopla valuation algorithm analyses property data on all 27 million UK homes on a continuous basis. We get our data from multiple sources including the government, estate agents, surveyors and our users. Our model looks at the relationships between transaction prices and property characteristics (type, style, # of bedrooms, etc.) and uses these patterns and trends to estimate present values. Because we add new data all the time, the range of homes for which we can provide instant estimates constantly expands, and the accuracy of our estimates constantly improves.
Our estimates are computer-generated. Such a computer-based value estimate system is often known as an Automated Valuation Model (AVM). We do this by using each distinct method in proportion to its likely accuracy impact for the specific property.
Our algorithm considers:
- previous sold prices for the specific property and recent transactions nearby
- changes in the market values to similar properties of that type in the local area
- the various characteristics of the property in question and those around it
- current asking prices for specific properties and others in the local area
- the size of the property in question relative to those around it
- the current values of comparable properties
Our models work on an extremely local level and adapt to the specific information available for each property, thereby creating a custom approach to valuing each property. There are effectively tens of thousands of models working together, each optimized for the accuracy of the small set of properties they exist to serve. New data is received continuously from a variety of sources and our systems are built to absorb this information quickly into the valuation process, allowing our estimates to take advantage of the most recent data available. Each day our valuation algorithm knows more than it did the day before.
How much data do you have?
We have tens of millions of data points on homes in the UK and are collecting tens of thousands more every day. In England and Wales, the publicly available transaction data is richer than in Scotland and it is non-existent in N. Ireland. Therefore, our model is likely to be less accurate in N. Ireland and Scotland than in England and Wales. However, because of our unique approach, which relies on the collective intelligence of our users about their homes and other properties that they are familiar with, we are rapidly filling in the missing data and our estimates become more accurate every day as a result. Every additional data point we gather on a home allows us to have a more complete picture and to improve the accuracy of the estimate for that property and similar properties nearby.
How accurate are the Zoopla Estimates?
Each estimate we provide has a related 'Confidence level' and 'Value range'. The Confidence level indicates the degree of accuracy of the Zoopla Estimate and is based on the amount of data we have for the specific home and for similar properties in the area, as well as the known accuracy of the models in this geography. The more accurate we know the models to be in this neighbourhood, the higher the Confidence level. The Value range indicates the likely current lower/upper values of a home based on our available data and varying market conditions. The size of the Value range depends on the Confidence level.
Our estimates are computer-generated. In the Real Estate industry, such a computer-based value estimate system is often known as an Automated Valuation Model (AVM). The accuracy of any AVM estimates can be limited by the range and accuracy of the data available to the model. Since the Zoopla model has not visited the properties for which it provides estimates, it only knows about the aspects of a property for which we have data. We are likely to be less accurate on unique homes (such as castles in remote locations) or properties that do not have comparable properties nearby, or on properties which have undergone radical renovation. Our data may be incomplete or inaccurate and you provide additional data to improve the accuracy and Confidence level by using the 'Refine estimate' links under any Zoopla Estimate.
We combine publicly available data such as sale transactions with our own proprietary data collected from estate agents, surveyors and our users. The more data we have, the more accurate the Zoopla Estimates are. Accuracy levels will therefore vary by location based on the amount of data we have for similar properties. You can help us to continue to improve our accuracy by sharing facts about your home - or anyone else's - using the 'Edit' links for the relevant properties under Home values.
We regularly test the accuracy of our estimates against both other AVMs available in the market and by comparing our estimates to recent transaction prices of properties that have sold. We consistently find our estimates to be the most accurate in the UK market and to be within 10% of the actual transaction price in the majority of cases. The table below shows our current accuracy measured against transaction prices achieved in key geographic areas.
|Post town||Median Absolute Percentage Error||
Proportion of estimates
|Newcastle Upon Tyne||11.2%||27.5%||45.6%||76.9%|
|Stoke On Trent||9.4%||29.4%||52.8%||75.4%|
- Median Absolute Percentage Error: Half the estimates are within this range of the selling price. For example, in Bristol, half the estimates are within 8.8% of the price for which the properties sell.
- Proportion within 5%: This proportion of estimates in this geography were within 5% of the selling price at the time of sale. In Southhampton, 35.6% of estimates are within 5% of the price achieved.
- Proportion within 10%: This proportion of estimates were within 10% of the selling price at the time the property sold. In Leicester, 53% of estimates are within 10%.
- Proportion within 20%: This proportion of estimates were within 20% of the selling price.
Remember - the more data we have, the more accurate our value estimates become. You may share data on any home using the 'Edit' and 'Refine estimate' links in the Home Values section of our website.
What is the Zed-Index
The Zed-Index is the current average Zoopla Estimate of home values in any given area. We have created it to measure changes in values over time in different areas and to provide a good measure of how individual property values compare to those around them. The Zed-Index is calculated as the mean of all Zoopla Estimates within any given geography.
The Zed-Index provides a good indication of how an area is performing in terms of value over time relative to other areas. If the Zed-Index for your area has gone up over the past say 3 months, then it means that the average home in your area is now worth more than it was 3 months ago. It is a useful guide to both buyers and sellers for evaluating how a specific home is performing relative to the area it is in and how the area is performing compared to others.
We believe that the Zed-Index is the best indicator of how the property market is performing since it takes into account the value of every home for which we have a Zoopla Estimate. We have created a Zed-Index for all areas of the country, from the UK as a whole down to every street in the country. So you can find out the Zed-Index for any region, county, town, street and even postcode. We update the Zed-Index for each area regularly at the same time as updating the Zoopla Estimates.
To see the Zed-Index for any area, simply use the search box under Home Values. You may also find the Zed-Index for different areas by conducting a search in the Home Values section of our website and using the Map view.
Disclaimer - the value estimates provided on our website are intended for general interest and information purposes only and should not be relied upon for any commercial transaction or similar use. These estimates are based on a) publicly available information which may be inaccurate or incomplete and b) typical properties in certain locations. They will not take account of any factors which are unknown to us and should therefore only be used as a starting guide to help determine what a home might be worth. None of the information provided is intended to be a substitute for independent professional advice and users are recommended to seek advice from suitably qualified professionals. We shall not be liable for any losses suffered as a result of relying on our value estimates.