How accurate is my location?

It is a radius, not a margin of error

The figure beside the answer above — ±8 m, ±120 m, ±3 km — describes a circle drawn around the position your device reported. Your device is saying it is somewhere inside that circle, and it is not saying where inside.

That is a different claim from the one a margin of error makes. You cannot average it away by standing still, and you cannot split the difference. ±8 m is a circle you could throw a ball across. ±3 km is a circle holding tens of thousands of front doors, and no amount of arithmetic gets you from one to the other.

It is also not a promise. The figure is your device's own estimate of its own confidence, reported by the operating system, and it is occasionally optimistic. It is still the most useful single number on the screen, because it is the only one that says how much of the rest to believe.

What makes the circle wider

Satellite positioning works by timing signals from satellites you have a clear line to. Everything that gets in the way costs you accuracy:

• A roof. Indoors is the big one. Signals are attenuated by the building and reflected by everything in it, and the fix falls back to whatever else is available.
• Tall buildings. In a narrow street between high blocks, half the sky is gone and the half you can see arrives twice — once directly and once bounced off the building opposite. That is why a city centre can be worse than open countryside miles from anywhere.
• A cold start. The first fix after opening an app is often the worst one. Give it a few seconds; the circle usually shrinks while you watch.
• Dense cover, deep valleys, vehicles. Anything between you and the sky.

When satellites are unavailable, your device positions itself from the Wi-Fi networks and cell towers it can hear, matched against a database of where those have been seen before. That works indoors, where satellites do not, and it is typically tens to hundreds of metres rather than single metres — sometimes a great deal worse, if the local database is thin or a router has been moved.

On Android there is one more case worth knowing: if you granted Approximate rather than Precise location, the wide circle is deliberate. The operating system is coarsening the position before any app sees it, and no app can undo that.

What the circle has earned

This is where the number stops being trivia. The accuracy radius decides how much of an address this site is willing to print.

Inside 60 metres, a house number is credible — and even then it is only printed if the building the map matched is itself within about 25 metres of you. Out to 250 metres, the street name stands but the number is dropped. Out to 1.5 kilometres, you get the neighbourhood or the village. Beyond that, a rough area and nothing finer. A postcode has digits masked rather than shown in full below street level, because a Dutch or British postcode is close enough to a doorstep that printing one you have not earned is a lie with an address attached.

So a wide circle does not make this site guess harder. It makes it say less.

Why the address can be vaguer than the coordinates

Two different limits are at work, and they fail independently.

Your coordinates come from your device. The accuracy figure is about them. The address is a separate step: a geocoder is asked what it has a record of near that point, and it answers with the nearest thing it knows — which can be a neighbour's door, a road rather than a building, or nothing at all in a development too new to be listed.

That is why a perfect fix can still produce a slightly wrong address, and why correcting the address here never moves your coordinates. The reasoning behind both is written out in full.