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Per km²: density, explained simply

A count of 3 means little on its own. 32 per km² is a number you can compare with any city on earth. Here is what 'Per km²' does, when to prefer it over 'Per 1 000 residents', and what it shows for bars across London.

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ByTinkal Gogoi(LinkedIn profile, opens in a new tab)September 4, 2026Updated October 21, 20266 min read

Three bars - is that a lot?

Take one hex - one hexagon on the map, about 350 m across (roughly 0.1 km²). It has 3 bars. Is that a lot? Compared with the next hex, maybe. But you cannot compare it with a street in Manchester, a planning report, or your own sense of what “busy” means, because 3 has no unit of space attached to it.

Per km² attaches one. It divides the count by the hex's exact size in square kilometers, so those 3 bars in a 0.09 km² hex become 32 bars per km² - a density, and a number that means the same thing in any city on earth. It is the simplest formula in the series, and the one whose value is easiest to underrate.

Per km²the field's term: Density

Bars per km² within a 10-minute walk. Density is peaky by nature: two cores in central London, in the West End and farther east toward Shoreditch, light up, and almost everywhere else is a fraction of them.

If every hex is about the same size, why bother?

Three reasons, and the third is the one people miss.

A unit anyone can compare

32 per km² can be set beside a figure from another city, a report, or a rule of thumb. 3 cannot, because nobody else uses our hex size.

Walks and drawn areas are not all the same size

A drawn area can be any size, and even hexes differ a little from one another. Per km² keeps every comparison honest, whatever the ground underneath.

It is the other kind of ratio

Per 1 000 residents asks how well people are served. Per km² asks how packed the ground is. Nightlife, footfall and competition are ground questions.

Switching it on

Set Count as to Per km². For the map below we also set Look at to Within a 10-minute walk, so each hex counts the bars you can reach on foot within 10 minutes, along streets and paths - nearer ones counting more (full weight under 3.5 min, 70% to 7 min, 40% to 10 min) - divided by the land of the hex and the hexes around it. That way the map shows neighborhoods rather than single hexes. In the Question Library, Nightlife density (“Where is nightlife densest?”) opens bars per km² ready-made.

Where to click

  1. Map type
  2. Amount
  3. Bar
  4. Count as: Per km²
  5. Look at: Within a 10-minute walk
'Per km² · Density' in the badge, and 'Bar per km², within a 10-minute walk' under it, with a Guide link to this post.
The same 'Count as' row every count carries. Per km² is available for any count, because land area is never missing.

Reading the map

Density maps are lopsided, and that is true, not a fault. A handful of streets in central London reach hundreds of bars per km²; most residential neighborhoods have a few, and 37 in every 100 hexes have none within a 10-minute walk. The legend splits that range into color bands - by natural breaks here, so each band edge sits where the values jump - and the center still glows while the suburbs sit dark.

Ten bands from 0.0 to 345 bars per km², chosen by natural breaks. The palette menu at the top right changes the colors.
Hovering a hex in south-east London, between Peckham and Greenwich: 66 bars per km² within a 10-minute walk. The brightest central hexes are several times that.

The math, honestly

Bars per km² in one London hex
Bars counted
3
Hex's sizethis hex's own size, printed rounded
0.09 km²
Per km²
3 ÷ 0.09 km² = 32 per km²

The card prints the size rounded to two decimals; the division uses the exact size, a little over 0.09 km², which is why the answer is 32 rather than 33. Within a 10-minute walk, the top of the division is the bars you can reach on foot, nearer ones counting more, and the bottom is the land of the hex and the hexes around it.

On a Score, click a hex and Hex details writes the division out with that hex's real count and real size: '3 ÷ 0.09 km² = 32 per km²'.
Show the math names Density, its one line of math and the source - Overture Maps, release 2026-08-19 - and the method card lists both formulas on the map. No small-numbers note, and that is correct.

Density is never 'adjusted for small numbers'

The per 1 000 residents post explains why a rate with three residents underneath it has to be pulled toward the city's value. A density has no such problem: 0.09 km² is 0.09 km² whether ten people live there or none. What density does inherit is the count's own coverage - a hex with no data has no density either.

Open bars per km² in London

The whole idea, in six lines

  • Per km² = count ÷ the hex's size in square kilometers. 3 bars in a 0.09 km² hex is 32 per km².
  • It turns a count into a unit you can compare with any city, report or rule of thumb.
  • It keeps drawn areas and hexes of slightly different sizes comparable.
  • Within a 10-minute walk, it counts the places you can reach on foot and divides by the land of the hex and the hexes around it.
  • Density maps are peaky by nature: the center glows, the suburbs sit dark, and the legend's color bands tell you the range.
  • Use per km² for ground questions - footfall, nightlife, competition - and per 1 000 residents for people questions.

Quick questions

What does 'Per km²' calculate?

The count in a hex divided by that hex's exact size in square kilometers. A MapBees hex - one hexagon on the map, about 350 m across - covers roughly 0.1 km², so 3 bars in a 0.09 km² hex is 32 bars per km².

If every hex is about the same size, why bother?

Because 32 per km² is a unit anyone can compare with another city, a report or a planning document. 3 is not. It also keeps drawn areas and hexes of slightly different sizes comparable.

How does 'Per km²' work within a 10-minute walk?

It counts the places you can reach on foot within 10 minutes, along streets and paths, nearer ones counting more, and divides by the land of the hex and the hexes around it.

When should I use 'Per km²' instead of 'Per 1 000 residents'?

Use per km² when you care about how packed a neighborhood is on the ground - nightlife, footfall, competition on a street. Use per 1 000 residents when you care about how well the people living there are served.

Does density get adjusted for small numbers?

No. The base is land area, which is never tiny in the way a resident count can be, so a density is shown exactly as computed.

See it on a real map

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About the author

Tinkal Gogoi(LinkedIn profile, opens in a new tab)Founder & Location Data Engineer

Builds MapBees's location-intelligence pipeline end to end — census and Overture Maps ingestion, H3 hex scoring, and the map interface — and writes the methodology behind every number on the site.