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Tableau | Data visualisation | Analytics

Length function to calculate lengths of spatial lines | New in Tableau 2023.2

In Tableau 2023.2 you can calculate the length of a line straight from the geometry, no more blending in distances.

Tim Ngwena •15 August 2023 •1 min read •7 min watch •1.3K

Part ofWhat's new in Tableau 2023.2 Tableau Functions

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The LENGTH function works only with line and multi-line string geometries, and you specify the units (miles, kilometres, feet, etc.) as a string argument.
You can skip working with the raw geometry and just use the calculated length for analysis, such as finding the Grand Union Canal as London's longest water body at 23.88 miles.
Accuracy depends entirely on how detailed the source geometry is, and more detailed polygons mean larger file sizes, so some generalisation is expected.
You can wrap the LENGTH function around the outline function to measure the distance around a polygon boundary.
Watch out for multi-polygon wards, as adding the polygon ID reveals that some boundaries are combinations of several polygons, which affects the calculated outline length.

0:00Hey it's Tim here and 23.2 you can now

0:02calculate the length of a line or a multi-

0:05line geometry

0:06easily inside a tableau meaning you don't

0:08have to blend in lengths and distances

0:10anymore,

0:11you can calculate them as long as you have

0:13the spatial object available in tableau.

0:15To find out how let's get started. Okay so

0:17here we have water bodies in London, this

0:20is a very basic

0:21data set, I've used it in the past and I

0:22think it's just a nice way of showing this

0:24feature.

0:24If I right click on geometry and I go ahead

0:27and create a new calculated field,

0:29you can see that I've already got the

0:31length function here set up. So all you

0:33need to do is

0:33give it the spatial object and the units of

0:35course it only works with line and multi-

0:37line string.

0:38It'd be interesting to see if you create

0:41the outline of an object, if it can

0:44actually calculate

0:45the distance around that. So we're going to

0:47try that as well because the outline

0:48function

0:49is a new object in this particular release.

0:51So let's go ahead and do this, let's go

0:53ahead and

0:54calculate length and you can see here that

0:56we get the function put in and all we need

0:58to do is add a

0:59comma and then do two speech marks and then

1:02put in mi feet. You can do kilometers,

1:05miles, whatever units

1:06you type in is what it will apply. You can

1:08see in the example they've got feet so let

1:10's go ahead and

1:10call this length and spell that correctly

1:14and then after we've done that hit apply

1:17and there we go.

1:19We have the function that's pretty much it

1:21here, it's dead simple. We can actually

1:23drag the length

1:24onto the label just to see that it's

1:25working nicely. We should see the lengths

1:28pop up and

1:28don't forget these are in miles so we can

1:30already see these working nicely. Now what

1:33's the use case

1:33for this? Well actually it's for being

1:36analytical frankly. If you've got these

1:38water body names and

1:39you know you have the relevant geometries

1:41in your data set what you can actually do

1:42is skip the

1:43geometry, calculate the lengths with the

1:45geometry but then just use the length for

1:47whatever type of

1:47analysis you're trying to do. So I want to

1:49know which is the longest water body in

1:51London, it's

1:52the Grand Union Canal and I can tell you

1:54that it's 23.88 miles. Now of course this

1:58is only going to

1:58be as accurate as the geometry and geomet

2:00ries are super interesting because the more

2:02accurate they

2:03are the larger the file type tends to be.

2:05Let's say you're trying to do the geometry

2:07of the outline

2:08of the United Kingdom, if you do that

2:10accurate to as much detail as you possibly

2:13can that's probably

2:14going to be a data set too big for putting

2:15inside of something like Tableau. So there

2:17is a little

2:18bit of generalization that goes on and so

2:20you have to bear that in mind with spatial

2:22objects

2:22but nonetheless it should be okay as an

2:24approximation and something you can use.

2:26Another use case is if you've got spatial

2:29objects let's say GPS traces you can bring

2:31those into

2:32Tableau and you can start analyzing

2:34different routes taken by certain modes of

2:36transport.

2:36Maybe you work for a delivery or

2:38distribution company and you do track the

2:40routes that your

2:40vans are taking you could try and optimize

2:43a little bit on those routes by seeing

2:45which ones

2:45are you know performing the best but you

2:47could also use things like travel time

2:49against that

2:50to kind of try and find where the sweet

2:51spot is. Another use case is you could use

2:54this to do all

2:55sorts of calculations to do with the impact

2:57on the environment for example if you're

2:59traveling

3:00further are you using more fuel and

3:02therefore are you causing more of a co2

3:04issue in terms of the

3:05way your co2 emissions are calculated. So

3:07these are all particular use cases that I

3:10think you can

3:10start to use this for that are actually

3:12quite relevant in the current climate but

3:14also quite

3:14useful. Now I also did say that we can

3:18potentially find the distance or the length

3:21of an outline of a

3:23outline created from a polygon inside over

3:27new geometry. So let's go ahead and I'm

3:29going to open

3:30up an old viz that I've already created

3:32that's actually already available on Table

3:34au Public.

3:34We're going to see if that works let's

3:36switch over to that now. Okay so here I am

3:38looking at the

3:39previous video I made on the outline

3:41function you can see I already have all

3:42these outlines.

3:43What I want to do is take this outline and

3:45see if I can wrap it in the length function

3:47to calculate

3:48the distance around the boundary. That's

3:50sort of an interesting calculation we can

3:52do. So let's go

3:53ahead and create a calculation using the

3:56outline of the wards and all we're going to

3:58do is we're

3:59going to go ahead and use the length

4:01function. So let's go ahead and search for

4:03it this way

4:04and we'll just double click the length and

4:06it will ask us okay how do you want to do

4:08that and again

4:08we'll do it in let's do it this time in

4:11kilometers just to show something different

4:14and we'll say

4:15outline length in kilometers and let's go

4:21ahead and do this and boom and hit apply.

4:25That seemed to work no complaints there and

4:29so we can go ahead to the different names

4:34okay and we

4:35can see which boundary has the largest

4:39outline that's quite nice it worked that is

4:43pretty cool.

4:44So we could sort this out and we can see

4:47here that Darwin actually has the biggest

4:50sort of outline

4:51that doesn't mean it's got the largest

4:53error or anything it just means it's got

4:54the largest outline

4:56and there are some other ones here for

4:58example village just looks like it's been

5:00it's been sort

5:00of cut short I don't think if it's it's

5:03kind of strange I don't know I don't know

5:05if that's

5:06let's do this let's just put the polygon id

5:09inside of this and yeah you can see this

5:11one's actually

5:12a combination of multiple polygons so if

5:14you put the polygon id what it does is some

5:16of these areas

5:17are sometimes multi-polygons coming

5:19together and so actually when you break it

5:21down like that it's

5:23actually a lot smaller so you can see that

5:24this is working a lot better and you can

5:26see all of the

5:27different ones so it's kind of something to

5:29be aware of when you're doing this you have

5:31to really

5:31think through sort of what you're trying to

5:34do and make sure it works but in in real

5:36terms it is

5:36actually able to let's say take if you just

5:40got a single single polygon let's take for

5:44example

5:44Elm Park or Chrome all of these ones here

5:46they just have a single polygon making up

5:49that specific

5:50ward so then you're able to go and figure

5:53out the distance of the outline so you can

5:55do that very

5:56easy I don't know what kind of use that

5:57might be maybe you're trying to figure out

5:59how much

6:00fencing you need to put up around a

6:02specific area or you're trying to visualize

6:04you know how many

6:05miles of coverage you're going to have to

6:07put to cover a boundary this is a really

6:09nice way of doing

6:10it really quickly inside of Tableau because

6:12again you can get a rough estimate and you

6:14can start to

6:14work with really large distances but give

6:16yourself a good sort of leeway for that but

6:18remember the

6:19accuracy can be hit and miss depending on

6:21how detailed those polygons are in the

6:23first place

6:24okay that's pretty much it thanks for

6:26watching this video and I'll catch you in

6:27the next one

6:28you

6:38[BLANK_AUDIO]

Rollup

Tableau 2023.2 adds a LENGTH function that calculates the length of line or multi-line geometries directly, so you no longer need to blend in pre-calculated distances. It also works when wrapped around the outline function, letting you measure the perimeter distance of polygon boundaries.

Demonstrated on a dataset of London water bodies (lines) and a separate viz of London ward boundaries (polygons) built with the outline function from an earlier release.

The Breakdown

Build the length calculation 0:18

Create a calculated field using the LENGTH function, pass it your spatial geometry field, then add a units argument as a string (e.g. "mi", "feet", "km"). It only works with line and multi-line string geometries, not polygons directly.
Check it on the label 1:21

Drag the new length field onto Label to confirm it's returning sensible values in the units you specified before using it further.
Use lengths for analysis, not just display 1:33

Once calculated, you can drop the raw geometry from view and use the length value itself for analysis body, ranking or filtering — for example finding the longest water body rather than just showing each one's length.
Accuracy depends on source geometry detail 2:01

Results are only as accurate as the underlying spatial data; highly detailed geometries produce larger file sizes, so real-world datasets are often generalised, giving you a good approximation rather than an exact figure.
Other use cases 2:20

The same approach applies to GPS traces for route analysis (e.g. optimising delivery routes against travel time) or environmental impact calculations like fuel use and CO2 tied to distance travelled.
Wrap LENGTH around outline to measure perimeters 3:41

You can nest the LENGTH function around the outline function on a polygon field to calculate the distance around a boundary — a further step beyond simple line lengths, useful for things like estimating fencing or coverage distance around an area.
Watch for multi-polygon wards 5:01

Some boundaries that look like a single shape are actually combinations of multiple polygons; adding the polygon ID to the view breaks these apart and gives a much more accurate, smaller outline length per polygon rather than one inflated combined figure.

Worth Knowing

LENGTH only accepts line or multi-line string geometries — you can't call it directly on a polygon, hence wrapping it around the outline function.
Perimeter/outline lengths can be misleadingly large if a boundary is actually made of several polygons merged together; check with polygon ID before trusting the figure.
More detailed, accurate geometry means larger file sizes, so expect some generalisation in your spatial data and treat lengths as estimates, not exact measurements.

Use It When

Reach for this when you need distances or perimeters from spatial data already in Tableau — route lengths, waterway or boundary lengths, coverage estimates — without having to pre-calculate and blend them in from another source.

How this Rollup was made provenance & method

A Rollup is drafted by AI from the video's transcript, then reviewed and edited by Tim. Everything used to produce this one is listed below — the model, the exact prompt, and the source video — so the process is transparent and reproducible.

Transcription: On-device — NVIDIA Parakeet v3 for recent videos, OpenAI Whisper large-v3 for earlier ones. The transcript never leaves the machine or gets published.
Drafting: Claude Sonnet 5 in the cloud, from that transcript.
Prompt: The exact Rollup prompt (v2) — the full system prompt, unedited.
Source video: Watch on YouTube
Drafted: 5 July 2026 at 09:38
Reviewed & edited: 5 July 2026 at 09:41 · by Tim Ngwena

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