How to Measure Your Sit Bones – Bike Saddle Size & Fit


bike saddle seat bone measurement

Riding a bike can become very uncomfortable if you don’t have the right saddle width. Usually, it’s not really an issue if you go for a short ride but longer rides will become an issue. To get the right saddle you need to first measure the width between your sit bones, but there’s much more to it.

You don’t always have to buy a new saddle, inconveniences can be caused by bad posture or incorrect saddle positioning and sometimes a saddle that’s not cut out for you.

I’ll go into other solutions at the end of the post but first, we’ll start measuring the distance between the sit bones. After that, we’ll look at proper saddle height and positioning and other factors you need to consider before you decide to get a new saddle.

Methods to Measure Your Sit Bones

Ok, first things first, I found a couple of ways to measure your sit bones to determine bike saddle width. Some may not work for you but I’m sure one of them will give you the correct answer. Try a couple and see if there are significant differences, some methods work better than others.

I would advise wearing the stuff you usually do when you sit on your bike to get the most accurate results, like shorts and bike shoes.

In order to determine the width, you need to measure between the center of your ischial tuberosities (these are the pointy lower parts of your pelvic bones). Grab something to measure with and follow the instructions below:

Aluminum Foil

  1. Take a piece of aluminum kitchen foil and place it on a carpeted chair or stair (anything with carpet will do.
  2. Find something to elevate your legs.
  3. Sit on the aluminum kitchen foil.
  4. Lean forward a bit to mimic your riding position.
  5. Lift your feet to leave an impression in the foil.
  6. Now you only have to the width between the two points of deepest impression.

Use erasers to sit on

  1. Get two small erasers or anything small to comfortably sit on.
  2. Put them on a chair and sit on them.
  3. Moved them until you can feel that they’re aligned with your sit bones.
  4. Measure the width between the erasers.

The Playdough Method

  1. Grab some playdough, enough to make an imprint.
  2. Put it between plastic foil and press it to make it about 2″ thick.
  3. Place it on a hard surface like a flat bench and grab something to rest your feet on.
  4. Sit on the playdough and mimic your riding position.
  5. Measure the width between the two imprints.

Here’s another approach:

Now look at the table below to see where you fit:

Sit bone width and saddle profile
Narrow Medium Wide
100mm or less 100-130mm over 130mm
3.93″ or less 3.93″- 5.12″  over 5.12″

Eureka! Now you know what type of saddle is right for you right? Wrong, there’s so much more to it than just the width between your sit bones. Let’s dig a little deeper before you splurge cash on a saddle that isn’t quite suitable for your body type.

Bike Saddle and Sit Bone Width Isn’t the Holy Grail

Even though you now know the right width, the measure of your sit bones and saddle with do not always correlate. There’s a lot more to it than just the width, like your weight, pelvis motion, the amount of soft tissue surrounding and your torso angle. Heavier riders need more support than skinny riders for example.

Measuring the width of your sit bones only applies when you sit up straight. You can try to mimic your position when you ride a bike but it’s not accurate enough. It should give a good first direction but there are more factors at play here.

When you ride a mountain bike or road bike, the saddle is higher than the handlebar. Climbing, descending or riding flat surfaces changes how your pelvis is positioned on your saddle.

Torso angle is often overlooked, a more aggressive rider needs a different type of saddle than someone who just likes to cruise. Another one is the direction of your pelvis movement, is the movement even distributed or more to one side?

Also, the quality of your bike, proper geometry and bike fit plays a part. There are many variables that determine what exactly is the right saddle for you personally.

Saddles themselves vary in shape and material, so think about the following:

  • How wide is the saddle at its widest point?
  • Which direction will the saddle flex towards?
  • How much slope is there on the side, how quickly does it drop off?
  • How quickly does it taper?
  • Is there enough flat surface to sit on the rear?
  • How soft is the cover, can it support your weight and how flexible is it?
  • Are the rails stiff/flexible enough and which direction does it mainly flex?
  • Etc…

Seat height

Now that we covered the measurement of sit bones it’s time to take a look at the proper seat height. Not only does the correct seat height helps riders to get max power transfer when stroking pedals, but it also prevents lots of problems with joints, muscles and foot problems.

So how do you get the proper seat height? It’s not hard to find out but first, let’s look if this is causing problems by looking at three indicators.

  • If you’re rocking in your saddle while riding your saddle is too high or too low.
  • Check your toe position, are they pointing in an angle when pedaling to make them go round?  This means your saddle is too high.
  • Maybe you’re compensating and sit on the nose of your saddle. This means your saddle is too high and will cause issues.

According to lab research from gebioMized lowering your seat height by just 5mm can reduce the maximum pressure by 15 to 20%. That is quite a lot.

Finding the Proper Height

There are a couple of ways to find your ideal saddle height. Just stand next to your bike and set your bike saddle even with the top of your hip bone. Wear your bike shoes if you have them to get the proper measurement.

This may be uncomfortable at first when you’re used to riding a saddle that site too low, but you’ll get used to it. Go for a short ride and see how it feels, if you feel unsafe drop it half an inch and try again.

Dropper Posts

One other solution is to get a dropper post which allows you to adjust your saddle height without stepping off your bike. Many riders use a fixed seat post and you’ll often find that it’s sort of a compromise when you ride different terrain.

You’re not getting the most out of your ride because the power transfer isn’t ideal. A dropper post allows for multiple seat heights making your life a lot easier. Set it low when you’re descending and back to the proper on flat terrain.

A Few Tips on Testing Saddles

Saddles are expensive, at least good saddles and you want to make sure to get the right one. It may require you to test many saddles before you get the right one. Fortunately, my local bike shop doesn’t mind if I return a saddle or anything I buy there so I hope you have a bike shop around that’s as flexible as mine.

The best thing to do is to start with a standard shape that’s suitable for your type of bike. It should be well adjusted and clamped towards the center of the rail. There should be enough flat surface you can properly sit on.

  • Start with a standard shape and ignore the fancy weird shapes for now.
  • Make sure it has plenty of flat surface in area you sit.
  • Rails should be close to the center of your seat post.
  • Depending on your pelvis movement you either need a flat saddle with abrupt sides or one with more edge.
  • Make sure it’s adjusted well and if possible clamped towards the center of the rails.
  • If possible you should test as many saddles as possible. Maybe borrow one from a friend or ask your local bike shop if you can test a few. Test them as you ride normally, not just ride a few blocks.

Conclusion

Even though it’s possible to measure the width between your sit bones to determine the saddle width of a bike, there’s much more to it than that. There are many variables that influence the proper saddle for you.

Sure, measuring sit bones works for your upright sitting position. In general, the whole surface of a saddle determines how comfortable a saddle feels, not just the width. You can still experience tingling sensations and numbness by just using this method.

I would advise against buying a saddle online because it’s such a personal thing. No matter how great the reviews are, a top of the line saddle may not be for you. Go to your local bike shop and ask about what you learned. Do another bike fit and test a few saddles, in time you’ll get the right one.

In the end, the best fitting saddle is the one that feels most comfortable when you ride. In order to find out, there’s only one way. test saddles as much as you can until you find the one that just feels right.

Ruben

I always had a thing for extreme sports and love almost anything that involves bikes and boards. I work part-time as a designer in the tech industry and work on my blogs whenever I can.

Recent Content