How a Sky Score is worked out
Type a postcode and you get five scores out of 10, and one overall score. This page shows where each number comes from, which one we estimate ourselves, and what none of them can tell you.
The short version
- Five scores out of 10, where higher is always better: Quiet Skies, Affordability, Price growth, Liveability and Environment. The overall score weighs them by what you care about.
- Almost every figure is a public body's own published data. Two we work out ourselves, and every answer says how: Quiet Skies where the official noise map has no figure, and how many planes pass overhead at the airports we can check against official figures.
- Where something isn't published, we leave it out and say so. We never fill a gap with a typical value, and nothing here is advice.
The lower the plane, the louder the ground below
A slice of London from Westminster to Heathrow, along the line planes follow when they come in to land from the east. Drag the round handle under the plane, or move the slider, to bring one plane in. Behind it, each building turns the colour of its yearly average aircraft noise: 49–51 dB at Battersea and 57–63 dB by Hounslow.
A strip of London seen from the south, from Westminster to Heathrow. A Heathrow arrival comes down the 3° glide path, from about 1,150 m as it passes Westminster to about 250 m over Hounslow, and lands on runway 27R. Yearly average aircraft noise under the flight line rises as it descends; it crosses the 50 dB contour 21 km out, 55 dB contour 12 km out, 60 dB contour 7 km out, 65 dB contour 3 km out. Westminster has none mapped.
How to read the picture
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The plane's path
A steady 3° slope down to the runway. The plane is drawn 5 times its real size, so you can see it.
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Straight down
The line from the plane to the ground, marked every 250 m of height.
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Noise lines
Lines from the government's noise map (DEFRA). Inside the 55 dB line, the yearly average is 55 dB or more. Each line is labelled where the plane crosses it.
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Noise colours
Behind the plane, each building takes the colour of its yearly average aircraft noise: under 50 dB or none mapped50 556065 dB and up That is a whole year of aircraft noise averaged, with evening and night counted as louder, not the sound of one plane. The World Health Organization's guideline is 45 dB, so every coloured building is above it. The slider is coloured the same way, along the plane's line.
What's above your home?
Type your postcode to see the official noise and air figures for your street.
About this picture: what is drawn, and how
A score, taken apart
Each score is out of 10, and higher is better. The overall score multiplies each one by its weight and adds them up. Here is Hounslow, the council area next to Heathrow.
| Score | Out of 10 | Weight | Points |
|---|---|---|---|
| Quiet Skies area band | 0.0 | 32% | 0.00 |
| Affordability official data | 2.1 | 27% | 0.57 |
| Price growth official data | 3.7 | 0% | 0.00 |
| Liveability official data | 7.2 | 27% | 1.94 |
| Environment official data | 6.5 | 14% | 0.91 |
| Overall score | 100% | 3.4 |
Quiet Skies is 32% of the score in this view. At 0.0 next to an airport, 3.2 of the 10 possible points are out of reach before anything else is counted.
For a whole council area, Quiet Skies is a band we set from the aircraft noise across it. A postcode inside Hounslow gets its own figure instead, so scores change from street to street. The points are each score times its weight; the overall score is their total, rounded to one decimal place.
The five scores
- Quiet Skies
- How free a place is from aircraft noise. 10 is the quietest. Where the government's official noise map covers a postcode, we use its figure. Everywhere else, we estimate it from the published flight routes.
- Affordability
- How cheap homes are, from the average price in the council area, compared with every council area we cover. 10 is the cheapest.
- Price growth
- How much prices rose over the last year, after inflation. Only the investor view counts it.
- Liveability
- Crime, school results, rail, metro and tram stations within an 800 metre walk (about ten minutes), and GP surgeries within 500 metres.
- Environment
- Air quality, road noise and flood risk.
A score always rises when a place is better, and is named for the good thing: Quiet Skies 8 out of 10. Some views turn the same reading round and name it for the bad thing: Aircraft noise 2 out of 10. It is one reading, shown two ways.
Official data, and our own work
Almost every number comes straight from a public body's own published data. Quiet Skies and planes overhead are the exceptions: we work them out, and every answer says how.
How Quiet Skies is estimated, and who publishes the rest
Our own work: Quiet Skies
Where the official noise map has a figure for a postcode, we use it. Where it has none, we estimate it from the flight routes published in the UK Aeronautical Information Publication (NATS): how close a postcode is to the routes and the runway, and how big the airport is. A whole council area gets a band we set from the noise across it. Where both exist, we check our estimate against the official map and publish how far off it is on the API page.
Official data
Prices from HM Land Registry, crime from the Office for National Statistics, school results from the Department for Education, stations from the Department for Transport, GP surgeries from the NHS, air quality and noise from DEFRA, and flood risk from the Environment Agency.
Some official data is itself a model, not a reading at your door. DEFRA's air quality and noise maps and the Environment Agency's flood map are worked out by those bodies from measurements and computer models.
How the planes are counted
The answer for a postcode says how many planes pass overhead on an average day, in three figures: on days the airport flies west, on days it flies east, and on days it uses both. Planes land and take off into the wind, so the weather decides which way an airport flies, and in many places that decides the day: under Heathrow's arrivals in Kew, hundreds on a day it flies west and a handful on a day it flies east. One average of the two would be true on no day at all.
What counts as overhead, and how the counts are checked
- Overhead means more than halfway up the sky (48.5 degrees or more) and below 7,000 ft: the Civil Aviation Authority's definition of an overflight (CAP 1498). How high a plane is counts from the ground beneath it, not from sea level.
- The planes are the positions aircraft broadcast as they fly, gathered by a community of volunteer receivers (adsb.lol). We count every day since January 2026.
- Checked every month. For each airport, the take-offs and landings we count must come within 5% of the CAA's own monthly figure. An airport that misses in any month is not shown at all, rather than shown with a gap.
- Which way. A day counts as one way when 80% of the airport's flights used that way; any other day counts as both ways.
- Where. Each postcode is read where the Office for National Statistics places it, on a grid of 100 metre squares. On the edge of a flight path, a few metres decide whether a plane counts as overhead, so where the squares around a postcode differ widely, the answer gives the fewest and the most within 100 metres. PO boxes and other postcodes for organisations that receive a lot of post are left out: they sit at a delivery office or a business, not at homes.
What the count leaves out: aircraft that do not broadcast their position (some small and military aircraft), and flying from airfields, heliports and airports we cannot check against official figures. Where that flying is a large part of what passes over, the answer says so, because few planes from the airports we count does not mean a quiet sky. It counts planes, not noise: how loud each one is depends on its size and height.
The overall score
Different people care about different things, so there are eight views. Each gives the five scores different weights, and a weight of 0% means that score is not counted in that view. Choose a view on the full map and the overall score changes; the five scores stay the same.
Show the weights for each view
| View | Quiet Skies | Affordability | Price growth | Liveability | Environment |
|---|---|---|---|---|---|
| Balanced | 32% | 27% | 0% | 27% | 14% |
| Family | 18% | 18% | 0% | 46% | 18% |
| Investor | 9% | 26% | 34% | 17% | 14% |
| First-Time | 16% | 43% | 0% | 27% | 14% |
| Quiet Life | 48% | 19% | 0% | 19% | 14% |
| Renter | 26% | 30% | 0% | 30% | 14% |
| Commuter | 21% | 30% | 0% | 35% | 14% |
| Later life | 36% | 14% | 0% | 32% | 18% |
When a score can't be worked out, for example where no school results are published, we leave it out and share its weight among the others. We never fill a gap with a typical value, and the answer says what is missing. Liveability and environment each need at least two of their parts, or that score is left out.
What it can't tell you
- How often planes fly over, away from the airports we count. There, the flight routes show where aircraft fly, not how many of them do.
- Anything about one particular home, such as its condition or its value.
- Which floor a home is on. The figures are for the postcode near ground level. Road noise and traffic pollution can be quite different on an upper floor; aircraft noise changes little from floor to floor.
- Whether a place is right for you. It is information to help you look, not advice.
- It is not a survey, a valuation or a conveyancing search, and does not replace any of them.
- Shares are of postcodes, not homes. "30% of postcodes" counts postcodes, and one postcode can hold one home or fifty.
Where the data comes from
Each figure's public body, under that body's own licence, with flight routes from the UK AIP (NATS) and aircraft positions from adsb.lol.
Every source and its licence
- Prices: HM Land Registry, UK House Price Index. Contains HM Land Registry data © Crown copyright and database right 2026. This data is licensed under the Open Government Licence v3.0.
- Crime: Office for National Statistics, Crime in England and Wales. Open Government Licence v3.0.
- Schools: Department for Education, Key Stage 4 Progress 8. Open Government Licence v3.0.
- Stations: Department for Transport, National Public Transport Access Nodes (NaPTAN). Open Government Licence v3.0.
- GP surgeries: NHS Organisation Data Service. Open Government Licence v3.0.
- Air quality and noise maps: DEFRA. Open Government Licence v3.0.
- Air sensors: Contains Breathe London data licensed under the Open Government License v3.0.
- Air monitors: © Crown 2026 copyright Defra via uk-air.defra.gov.uk, licenced under the Open Government Licence (OGL).
- Energy ratings: Energy Performance of Buildings Register (MHCLG). Open Government Licence v3.0.
- Flood risk: Environment Agency, Risk of Flooding from Rivers and Sea. Open Government Licence v3.0.
- Postcodes: Office for National Statistics, National Statistics Postcode Lookup, under the Open Government Licence v3.0. Contains OS data © Crown copyright and database right; Royal Mail data © Royal Mail copyright and database right; National Statistics data © Crown copyright and database right.
- Flight routes: UK Aeronautical Information Publication (NATS), drawn by Sky Score for the aircraft noise estimate. Public, but not openly licensed, and not for navigation.
- Planes overhead: aircraft positions from adsb.lol, under the Open Database License (ODbL) 1.0, so the counts we make from them are under the ODbL too. Weather at each airport from the Iowa Environmental Mesonet (Iowa State University). Ground heights from OS Terrain 50: Contains OS data © Crown copyright and database right, Open Government Licence v3.0. Checked against the Civil Aviation Authority's monthly airport figures.
Each licence covers its own dataset, not Sky Score as a whole.
How up to date it is
Each dataset is its publisher's latest. The one to know: DEFRA's noise maps describe 2021, a year with fewer flights and less traffic than usual, so they read quieter than today.
The date of each dataset
- House prices are HM Land Registry's monthly price index, now for August 2026. We update them each month.
- Noise maps are DEFRA's latest, published in 2022. They describe 2021, a year with fewer flights and less traffic than usual, so they read quieter than today.
- Air quality is DEFRA's latest map of yearly averages.
- Crime is the Office for National Statistics' latest year, updated when it publishes.
- School results are the latest Progress 8 figures. The government has paused the measure for two years, so these stay until it returns.
- Flight routes are rebuilt from the official aeronautical publication and checked on every release.
Places we don't cover yet
Sky Score covers 97 council areas in 13 UK city regions, plus New York's 5 boroughs and 50 Bay Area cities.
Outside these places a postcode answers "not covered yet", and we don't guess. A score built from another city's figures would be wrong in a way you couldn't see.
For every threshold and its source, read the full methodology. Developers can get the same scores, with their sources, from the API.