Are fitness watches accurate for calories? Are fitness watches accurate in general?

Tracking your fitness has never been easier with the various fitness trackers out on the market. But how confident can you be in their results? Are fitness watches accurate for calories at all?

Although progress has been made to reduce the margin of error, fitness watches are not 100% accurate. For now, they can be considered estimations that vary significantly with each individual device. They can be off the mark anywhere between 27% and 93%. 

But that’s not all you need to know about your fitness watch. Keep reading for other important information to see how it really works, and how to use it for your fitness goal. 

How do fitness trackers measure calories?

Each fitness watch differs in terms of how they measure calorie burn. Whether that is because of the algorithm used, variables considered, or just the technology in the watch itself. 

For this explanation, we will go over the process used by FitBit. They have an explanation of the system in their help articles.

First, your BMR, basal metabolic rate, is used as the base of the system. 

This is the minimum calories you use to keep your body functioning. Fitbit calculates BMR with your basic information such as gender, height, and weight. 

Your fitness watch will then adjust this number with your activity level and heart rate to give an estimated number of calories burned throughout the day. 

That is the basic generic process. 

Hopefully, this article helped you understand your fitness watches a little more, don’t forget to grab that maintenance calorie spreadsheet for yourself! <link>

The most accurate way to measure calories burned at home

You might be a little disappointed that your fitness watch is not very precise in the calorie estimation.

So what is the most accurate way to measure calories if you want to know that number?

While there are different options, let’s make it easy and pick one you can do by yourself. 

I’ll let you know how you can track calories accurately at home. 

Tools needed

The process

Measuring your calorie burn at home will take some time because we want enough data for a confident result. 

For two weeks you will need to weigh yourself at the same time, preferably after you wake up, before eating, and after using the restroom. 

In those same two weeks, track all your calories consumed as accurately as possible. 

For each day we will find out if you were in a calorie surplus or deficit with this formula

Yesterday’s calories – (Today’s weight change in pounds x 3500) = yesterday’s maintenance calories

For example, if we are 1 pound heavier than the day before we use the formula to give a solid answer. And let’s just say we ate 1800 calories. 

1800 – 3500 = -1700

Weight fluctuates greatly day by day, this is why one day is not an accurate representation and why the results might look weird like the one above. The overall long-term average of multiple days is what we aim to achieve. 

For example: 

Day 1 : 1800 – 3500 = -1700

Day 2: 1800- (-3000) = 4800 

The average for those two days is 1550 calories. So eating 1550 calories would have kept us at the same weight, anything more leads to weight gain, and anything less leads to weight loss

Once you have 2 weeks’ worth of data minimum, find the average. This number is your average daily maintenance calories during that time. 

You can do what you wish with this number, like comparing it to the calorie burn of your fitness watch. 

If this sounds a little complicated, I created a spreadsheet that automatically does these calculations, you can get it for yourself here.

How to use a fitness watch to lose or gain weight

So if fitness watches don’t accurately track calories burned, how can you use one to move your number on the scale? 

Don’t fret because I have a solution. 

That number we found before? It comes in handy here. 

For every day we found maintenance calories, we are going to also record the calorie estimate given to us by our fitness watch and find the average estimate over that same time. 

We are going to divide the estimated average by the maintenance calorie average. We are left with a ratio. 

For example: 

2300 estimated average / 1800 maintenance average = 1.27 . meaning that the fitness watch estimated 1.27 times higher calorie burn than the real number. 

Now just keep that ratio in mind when looking at the data your watch gives you and it suddenly becomes a lot more usable. 

Most accurate calorie counter watch 2022

While no fitness watch is perfect for tracking calories, there must be one above the rest in terms of performance, right? 

Well, the international journal of cardiology released a study in 2015, that reviewed how well Fitbit tracked calories. They found that this brand was fairly reliable and met criteria where the results could be used for the correct monitoring of health. 

That was 7 years ago, so the technology in Fitbit should have further improved by now. 

If you want to try one, check out the different options here