Calculating Stride Length

[sappy16]

Hi all,

I've been trying to calculate my walking stride length (actually step length, but Fitbit calls it 'stride length') to improve the accuracy of the distances that my Fitbit (Charge HR) shows.

I did a 20 mile walk in July so I have been using the data from that to try and calculate the stride length. I tracked the walk using both my Fitbit and RunKeeper on my phone, and have selected a just under 6km segment of the walk where I did not take any breaks to use in my calculations. I wanted to use this data as I figured over such a large distance, my steps should have been roughly what they would normally be.

The issue I am having is that my calculations show a step length of 35.72 inches. I am a 5 ft 7 female, in ok but not fantastic fitness. From everything I have read online, this step length seems enormous. I am not conscious of having an unusually long stride length. 

Walking kilometers 22.22 to 27.91 of the walk took me one hour, in which time my Fitbit tells me I took 6270 steps. So 6270 steps in 5690 metres, which gives a step length of 0.9075metres or 90.75cm. Converted to inches, this is 35.72. Have I missed something here? I am really struggling to understand why my step length seems to be so high. Does anyone have any suggestions?

I have added a screenshot of the steps chart from the Fitbit Dashboard. The walk was done at night (starting 10pm, finishing around 5am), hence the weird times! Kilometers 22 to 28 were between 2:45 and 3:45am.

Thank you.

[JohnRi]

Unfortunately you cannot do what you are trying to do with the data you have.  There is no way that any app, or tracker can accurately calculate your stride length.  Step counts are probably inaccurate, distances are roughly calculated.

To set your stride length you need to find a accurate distance you can walk.  I used a 100 yard football field.  I walked the known distance 3 or 4 times and counted my steps.  Turns out each time was the same step count.  Then I used that to calculate my "stride" length. 

But keep in mind that when you walk, your stride length changes.  It depends on how quickly you walk, vs power walking.  When I power walk I take short stride steps.  The more steps, the faster the walk.  So when I stroll, or walk around 2-3 mph, or powerwalk at 4.5 mph, each stride length is different.

You are not a machine, so each step is not the same.

[EricJRW]

I like what @JohnRi said. I tend to think of the stride length as an average. Every step you take is not the same. Maybe for parts of the day it is, but not all the time. When I did a rather scientific determination of stride length, I did it on a treadmill. Same speed, for long enough that the bars on the graph were all practically the same. What I found is that fitbit was "cheating" me, i.e. I walked farther than fb calculated, which means the fb stride was shorter than my own.

But what I think, that in an average day, many steps are are not full steps, so in fact maybe fb is correct in using a shorter stride, so that the distance averages out.

Just one of the many things I thought about in the early days of fb ownership.

Bottom line is it is just a number. A number to best. Keep moving, that's the goal.

[USAF-Larry]

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@EricJRW wrote:

When I did a rather scientific determination of stride length, I did it on a treadmill. Same speed, for long enough that the bars on the graph were all practically the same. What I found is that fitbit was "cheating" me, i.e. I walked farther than fb calculated, which means the fb stride was shorter than my own.

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Good point, @EricJRW, but remember that the stride length on a treadmill is almost never the same as it is in in natural walking outdoors.  A treatdmill is a measured, constant speed in which you get into a rhythm of taking steps. But when you walk outdoors you are constantly walking at slightly different speeds and different stride lengths.  That is why "average" stride length is important.

I did a test by walking on a marked quarter mile track, and counting the steps. I divided the number of steps by 1320 to get the average stride length.  I then repeated the process and calculated the stride length again. Both averaged about the same length, so I went into the app settings and changed the default stride length to my measured value. The Fitbit has been fairly accurately measuring my walks ever since.

[EricJRW]

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@USAF-Larry wrote:

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 I did a test by walking on a marked quarter mile track, and counting the steps. I divided the number of steps by 1320 to get the average stride length.  I then repeated the process and calculated the stride length again. Both averaged about the same length, so I went into the app settings and changed the default stride length to my measured value. The Fitbit has been fairly accurately measuring my walks ever since.

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@USAF-Larry Did you find your number to be larger or smaller than what fb was using? I noticed my fb liftetime distance changed when I modified my stride length.  can't find it now, but there was a post here how fb was calculating one's stride based on gender and height.

[USAF-Larry]

Fitbit counted more steps after I adjusted the the stride length, @EricJRW.  I have tested it several times on marked trails, and the distance is always spot on.

[engus]

To find your stride length find an area of flat dry pavement, wet the first section of the pavement. Then walk through the wet section continuing into the dry section at a normal walk. measure the distance in your stride.

[edberrey]

During walking, a step is the distance from when you pick up one foot and put it back down on the ground (ie pick up right foot, swing forward, put right foot on ground). A stride is the distance of both the right and the left step.  (2 Steps Equals 1 Stride)

[Cnlots]

This makes more sense, I’ve been trying to calculate my stride by taking my distance in inches and dividing it by the amount of steps that fitbit counts. This would get my step length. This amount seemed right, but it would always short me in distance. I only run on a treadmill, so I know my distance and time. Thanks for saving me a bunch of trial and error. Hopefully after updating it will be right. Thank you!