What a catchment area is and how to calculate it

A 500-metre circle on the map tells you that you reach a lot of people. The reality changes depending on where you are: if your premises face a major avenue, a river or the railway tracks, a good part of that circle is people who will never cross over to reach you. You'll see the same thing in Madrid, Paris, Lisbon or Milan. The difference between a radius and a real catchment area is the difference between a business that meets its forecasts and one that inflates them.

What a catchment area is (and what it isn't)

The catchment area is the physical zone that most of your customers come from. It sounds obvious, but it hides a trap: it isn't a circle. It's the shape that real streets draw when someone travels 5, 10 or 15 minutes on foot, by bike or by car from your premises.

If you draw it as a circle, you ignore that a river blocks the way, that a ring road or an urban motorway acts as a wall, or that a steep hill puts off almost anyone. The consequence: you count customers who are never going to come.

The 3 layers of the catchment area

• Primary (5-10 min on foot): 60-70% of your customers. They come without a second thought; they're the ones who'll decide whether your business survives. Example: the bakery on the corner of your street. If they fail, no second layer can save it.
• Secondary (10-20 min): 20-30%. They come for something specific (product, price, brand) but not out of habit. A dental clinic, an English-language school.
• Tertiary (more than 20 min, now by car): 5-15%. They only travel for you if you're a destination: a starred restaurant, a unique specialist shop.

A counter-example of a typical mistake: a neighbourhood pharmacy treating its area like a Decathlon. The primary layer is almost everything; the rest is statistics.

The 4 steps to calculate it, in order

1. Decide the mode of travel your customers use

A café: on foot, 5 minutes. A car dealership: by car, 20 minutes. A gym: by bike or on foot, 10 minutes. If you get this wrong, everything that follows is wrong too.

2. Calculate the isochrone from your point

The isochrone is the real polygon you reach by following streets, not straight lines. It's what replaces the circle of the radius.

3. Cross-reference with population and income

Inside that isochrone: how many people live there, what their age is, what their average income is. That data comes from each country's statistics institutes, not from back-of-the-envelope estimates. That's how the area turns into a number of potential customers, not a blob.

4. Subtract overlaps and barriers

If you already have another site, deduct the part of the catchment area they share. And check by eye whether a fast road or a river leaves half a zone unreachable even though the isochrone draws it in.

An illustrative example: the same dental clinic, three different areas

Let's take an invented case purely to see the mechanism. The figures below are round and instructive: they are not real data from any city. When you apply it to your business, the real numbers come from the official sources for each city. Suppose you open a private dental clinic and compare three locations with the same 10-minute walking isochrone.

Imagine a well-established central area: high density, lots of people packed into a small area and an income clearly above the city average. Let's say, by way of illustration, around 45,000 inhabitants within the isochrone and a high percentage of people with higher education. Density and purchasing power to sustain a private service.

Now imagine a residential outskirts with an income close to the average and fewer people per square metre. The same isochrone touches perhaps half as many people with a profile that matches your prices. Same plan, different reality: the isochrone is drawn the same way in both places, but the people who live inside are different.

And in between, a neighbourhood in transition with income somewhat above the average: an intermediate profile, which would suit a clinic with mid-range rather than premium prices. The conclusion isn't the specific numbers, but the method: the same shape on the map, different decisions depending on who's inside.

What you really use it for

• Comparing candidate locations: on paper, two premises with the "same" area can have 18,000 or 31,000 reachable inhabitants. Decide with numbers, not with the feeling you get on a walk.
• Defining your advertising radius: if Meta Ads or leaflet drops cover beyond your primary layer, you're spending on people who will never come.
• Mapping out your delivery area: 15 minutes by motorbike, not 5 km. The difference between reaching 40,000 or 12,000 households.
• Planning expansion without cannibalising: when opening a second premises, the first thing is to see whether its area overlaps the first one's. If it does, you're stealing from yourself.

The circular radius: why it almost always lies

Three reasons never to use a circle:

• It doesn't respect the street network. In an old town with an irregular layout, like those found in so many European cities, 500 metres in a straight line easily become 900 metres of actual walking.
• It ignores urban barriers. A motorway, a river, a railway line or a steep gradient cuts off the flow of people. The circle counts everyone equally; reality doesn't.
• It doesn't distinguish between modes of transport. 1 km on foot is 12-15 minutes. That same kilometre by car, at rush hour and in a congested city, can take considerably longer. The same kilometre means two different things.

How much does it cost to calculate it properly?

• By hand (DIY): €0, 2-3 hours per premises. Google Maps "Directions" trying several addresses, plus a spreadsheet with the population per neighbourhood that your country's statistics institute publishes. Enough if you have a single point and an approximation will do.
• Consultancy: €600-1,500 per point. They deliver a report with isochrones and cross-referenced demographics. Useful for an investor dossier, expensive for comparing 10 areas.
• A tool like POINOVA: from €0 to start (2 isochrones per day; 10 with Pro and unlimited with Advanced), 1-2 minutes per area. You change the mode (on foot/by bike/by car) or the minutes, and the isochrone is recalculated with the population living inside it and their income, where data is available.