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Some bike shops have gel pads that you sit on to measure the distance between your sit bones. Is it possible to take this measurement on your own at home, or does this really require special-purpose equipment?

[Related question: Should I use a narrower saddle on a road bike than I would on my hybrid commuter?]

  • I came across another suggestion, which I'll include for completeness: sitting on a ziploc bag containing flour. – amcnabb Jun 19 '12 at 23:17
  • This only works with a very strong bag or a very light rider. Not something my wife would be happy about me trying. :) – zenbike Sep 9 '12 at 2:57
  • Another suggestion I saw was to use aluminum foil over a towel. – amcnabb Sep 11 '12 at 3:52
35

Copied this from a saddle mfg website: How to measure your own sit bones

Of course the measure you really want is between the centres of your ischial tuberosities – the pointy lower parts of your pelvic bone on either side. Many bike dealers have a pad that you can sit on to measure this distance, but you can do it at home too.

Take a piece of aluminium kitchen foil and place it on a carpeted stair. Sit on the foil, lean forward a bit to approximate your riding position, then lift your feet. This should leave a good impression of your rear in the foil, and you can measure between the two points of deepest impression to get your sit bone width.

‘Narrow’ sit bone width would be 100mm or less, medium 100-130mm, wide over 130mm.

A saddle’s width is measured from edge to edge across the top, and Specialized recommends a 130mm saddle width for narrow, 143mm for medium and 155mm for wide. These figures should translate approximately across other ranges, with all other factors taken into account.

  • 2
    This is the only home method that worked for me. Couldn't get the cardboard method to work. – user1816847 Nov 2 '14 at 5:54
  • One can use old-school mouse pad (those with flex). Specialized went pretty vague when selecting the saddle -- the numbers they gave translate into adding around 3 cm to your sit bones width in given position. – greenoldman Apr 5 '15 at 15:36
  • Thanks, I've been wondering why the Fizik Arione has been so massively uncomfortable for me.. this explains it. – John Hunt Feb 7 '18 at 21:55
16

None of the above techniques worked for me. I made no impression on the corrugated cardboard and the foil just showed a nice big bum-print after sitting a few different surfaces. I came up with my own technique that's a bit more trial and error but seemed to work for me.

I got two small erasers, put them on a chair, sat on them and moved them around until they felt like I was sitting on my sit bones. Then I got up and measured how far apart they were.

9

I know this is an old thread but it's the top one on Google and I found it helpful. I tried all the methods above and I didn't have a lot of luck so I wanted to share what I tried.

I made some playdough using the first no cook recipe I found on Google (it was fun and doesn't take long). I then put it between two pieces of cling film and pressed it to about 2" thick, placed it on a hard surface (my kitchen floor) and put a tea towel over it so my legs didn't stick to the cling film. I then sat on it with my back in roughly my riding position. The impression of my sit bones is really clear, I can see 2 circles (see image) and I measured the distance between the centres. I tried a few times and it was consistent.

enter image description here

8

You can do it on any surface which will conform to the shape of your butt, like a piece of memory foam.

Sit on it, with your knees higher than your seat by 4-6 inches, then measure the center of the depressions left.

There are different types of memory foam, and some will have a more durable impression than others.

7

I've used this method which worked well:

  1. Fill a large size ziploc bag with icing sugar. Icing sugar's fine texture means that it binds together when compressed. This is what we want - it will hold the shape of your buttprint after you get up.

  2. Close the bag making sure to squeeze out the air.

  3. Place on hard chair.

  4. Sit while assuming the degree of forward rotation that you intend to cycle with. The distance between your sit bones change depending on this rotation.

  5. Get up cleanly and measure the distance between the depressions.

  • 5
    Sweet! (What else can I say?) – Daniel R Hicks Sep 1 '13 at 12:55
  • 1
    I can see some explaining to the wife if you don't get all the air out......There has to be a sitcom episode in this idea...... – mattnz Sep 2 '13 at 6:50
6

A fresh piece of corrugated cardboard on a hard surface such as a coffee table. Sit down and try to mimic the upper body position you have on your bike. Your sit bones change position based on how your pelvis is tilted. Your sit bones should crush the corrugated cardboard slightly and leave two indentations. Measure center to center as best you can.

  • You can't mimic your riding position, and get an impression of your sit bones. Using the position with your knees 4-6 inches above the impression material matches the method that manufacturers are using to get data to build their saddles, and is thus the most likely to match with the recommendations available on the market. – zenbike Sep 9 '12 at 2:55
  • I should have quantified that my coffee table, if it were a bike, would be categorized as a low rider... – 802bikeguy.com Sep 18 '12 at 4:10
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    Wouldn't it make more sense to do this on a bike? – Neil Fein Dec 2 '12 at 19:52
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    @NeilFein That's a catch 22. You're assuming the saddle on your bike will hit your sit bones correctly, in which case this whole exercise is redundant. – meagar May 27 '13 at 18:08
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    This works better if you can peel off one flat side of the corrugated cardboard, leaving the bare ridges exposed to sit on. The thicker the cardboard the better too. – Criggie Jan 21 '16 at 20:33
6

Here's a link to a video that may help you:

In this technique all you need is a piece of corrugated cardboard and some chalk.

  • Nice video. :) Thanks for the reference. Nothing like a video. Worth a 1000 images. – Paulo Matos Jan 3 '17 at 14:49
3

There is one more method people here aren't talking about... Sit on a bike on a trainer, get into riding position, and have someone you don't mind touching you physically measure your sit bones, in proper riding position. You can feel someone's sit bones on their butt. They're pretty obvious once you're touching them.

-1

Find a manageable hard flat surface

1 sheet fairly damp kitchen roll paper
2 sheets of dry kitchen roll paper on top

Sit down on paper and lean forward to 45 deg

Very slight wiggle your arris

Stand up

Measure centre of indents

Mine = 110mm

Therefore 145 saddle size.

  • Welcome to the site. I found this a bit hard to read, could do with more full stops and clearer sentences. Seems like a good cheap tip! – Swifty Apr 6 at 18:24
  • This is pretty much the same as the corrugated cardboard suggestion from 2012, but uses a different paper product. – Criggie Apr 7 at 9:49

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