
• #2
It could be done. We would need to define a calculation based on steps for walking then maybe heart rate when moving faster than 5km/hr. 5k/hr is about the upper limit of most people's fast walk speed, anything faster is jogging. We would also need an app to store your weight and maybe height.
Note that fitbit would just say you burned so many calories per hour just sat still. Just breathing burns calories. I think about 1800 per day, depending on weight and heart rate.
As having heart rate on all the time uses a lot of battery the app would maybe have to be a widget that turned heart rate on when faster walking was detected.
A basic approximation could just use weight, elapsed time and steps. I suspect early fitbits did not do much more than that.

• #3
That would be great if someone has the understanding to make an app for it. It would pair well with the Run app.
This article describes a formula to get the calories burned. You're right about the metrics of steps, heart rate, height and weight all being key to calculating the total. Even if it's not ultra precise, having even a general idea of how many calories burned would be great.
https://www.verywellfit.com/howmanycaloriesyouburnduringexercise4111064

• #4
This link has got MET rates for various activities.
https://www.healthline.com/health/whataremets#examples
Sitting 1.3 MET to Running 7mph 11.5 METS
We also need the MET count for breathing and sleeping.I am fairly sure I could leave a fitbit on the desk and at the end of 24 hours it would say I had burned 1800 calories.
But based on the above we could use the heath app steps recorded per hour as a proxy for the level of activity and calculate METs from that.
I am just doing a back of the envelop calculation below, to see if the answer makes sense.
7 MPH is 11.5METS
7 miles => 11265m => 11265 / 0.75 = 15020 steps in 1 hourWhere 0.75 is my stride length (can be approximated from height for the person)
There is a formula somewhere for that, need to find it.0 steps > 15K steps in 1 hour
1.3 to 11.5 Mets
So that transcribes to a rate of(11.5  1.3) / 15020 ==> 0.000679 MET per step per hour.
So say I do 2K steps in 1 hour
My MET rate would be 2000 * 0.000679 => 1.358So I walk 6000 steps in 1 hour => 4.074 METS
I am 80KG
Total calories burned = Duration (in minutes)*(MET*3.5*weight in kg)/200
=> 60 * 4.074 * 3.5 * 80 / 200 => 342 calories
RESULT: Thats a believable answer !!!!
So I think we just need the background constant METS for being alive.
Is it 1.3 (the sitting at a desk value or 1 ?).QUESTION: Lets calculate 24hours of no exercise (ie no steps)
Total calories burned = Duration (in minutes)*(MET*3.5*weight in kg)/200
Lets try a MET rate of 1.=> 24 * 60 * 1 * 3.5 * 80 / 200 => 2016 (ooh that is close to 1800 cals).
If we use a MET rate of 0.9 as the sleep value we get 1814 cals. Which is very close to the fitbit value of calories burned when you leave it on the desk for 24 hours.
So I think we have a way to calculate this.
Ideally we would just add this into the Health app and add a setting in the Health App to Age Height (to work out stride length) and Weight in KG.

• #5
This looks excellent and a believable answer is all I'm looking for. From what I've seen, all the mainstream trackers like Fitbit etc give varied results for calculating this so it doesn't need to be that precise. This looks like a great start to the math! Thanks for indulging the idea and drawing up some calculations.

• #6
Step Length Calculation  needed to work out the height to step to MET profile up to 7mph
https://dotorg.brightspotcdn.com/6b/bf/e07786f54254b9a5e0e9863dcfa9/stridelengthbyheight.pdf
Females: h (inch) * 0.41
Males: h (inch) * 0.415Conert to metric height
male step length = h (cm) * 0.415 / 100 in meters
female step length = h (cm) * 0.41 / 100 in metersMy height is 5ft 8, 68 inch or 173cm
stepl = 173 * 0.415 / 100 => 0.717m

• #7
Basal Metabolic Rate (Calories burned for resting for 24 hours)
https://www.omnicalculator.com/health/bmrharrisbenedictequation#howcanyoucalculateyourbmr
Your basal metabolic rate (BMR) is equivalent to the amount of energy (in the form of calories) that your body needs to function if it were to rest for 24 hours.
For men: BMR = 66.5 + (13.75 × weight in kg) + (5.003 × height in cm)  (6.75 × age)
For women: BMR = 655.1 + (9.563 × weight in kg) + (1.850 × height in cm)  (4.676 × age)
For me:
BMR == 66.5 + (13.75 * 80) + (5.003*173)  (6.75*61)
66.5 + 1100 + 865  412 => 1619.5 (this is for 24 hours)For each hour of sleep therefore => 67.5 cals
Are there any apps for Banglejs 2 that offer calories burned estimate? It’s one of the features I’d like to use in a smart watch and many of the mainstream fitness watches seem to offer it.