A weight loss calculator is a great place to start a weight loss journey as it can take the guess work out of how many calories you should aim to eat each day to reach your goal.
People tend to over complicate things when trying to lose weight.
It’s essentially this simple:
Track how many calories you’re eating. Figure out how many calories you’re burning.
Make sure the amount of calories you’re burning is less than the amount you’re eating.
Okay, sure there are exceptions, but generally speaking, that’s the basis of what you need to know if you’re trying to lose weight.
Now that I’m off of my soap box, let’s talk about how different weight loss calculators use actual science and math to help you lose weight – and keep it off.
Different Kinds of Weight Loss Calculators
There are quite a few different kinds of calculators out there that can be great tools for helping you to lose weight.
Each calculator takes different inputs in order to provide you with different tool to reach your weight loss goals – each serving a different purpose, but all useful when used correctly.
Here are some of the most popular types of calculators that might be useful during your weight loss journey.
All of the calculators mention will be at the end of this article for you to try.
A calorie calculator gives you a pretty good idea about how many calories you should be eating to lose weight.
One of the most common problems people make when they’re struggling to lose weight is underestimating how many calories they’re eating while also overestimating how many calories they are burning.
A calorie calculator won’t fix that problem (you’ll need to actually track your food for that), but at least it will tell you how much your should be eating, or at least a range to aim for.
Calorie calculators typically will ask for your age, current weight, height, gender, and activity level.
More advanced calories calculators, like this one, will not only tell you how many calories you need to eat to lose weight, but they can tell you:
- How long it will take you to reach your goal weight
- A break down of your estimated weight loss day by day if you were to follow it’s recommended calories.
My calorie calculator is the more advanced option, where I show you the day by day breakdown.
Because that would take up a ton of room, and it’s nice for you to take have a personal copy while you’re using it daily, just fill out this form and I’ll send you your own customizable calorie calculator!
Get your own customizable calculator:
How Calorie Calculators Work
It uses your inputs to determine your BMR, or Basal Metabolic Rate.
There is then a set number to multiple your BMR by based on your activity level in order to determine how many calories you need to eat in order to lose weight.
We’ll get into BMR, the basal metabolic rate calculator and what these set amounts are more below.
Macro, or macronutrient calculators, are similar to calorie calculators but take a slightly different approach and are one of the most useful types of weight loss calculators.
Macros are the three major categories that are foods are made up of: carbs, protein, and fats.
A macro counting is a very successful way of eating to lose weight.
It’s also commonly referred to as flexible dieting or IIFYM (If It Fits Your Macros).
The idea is that you can eat whatever you want, as long as you get a certain number of proteins, fats, and carbs that day.
Sound crazy? About 5 years ago, I lost over 40lbs eating this way and have been doing so ever since.
Okay, getting back on track, how does a macro calculator work and help us to lose weight?
Similar to the calorie calculator, it takes generally the same inputs, but instead of telling you how many calories you need to it, it outputs how many grams of carbs, protein, and fats you should be eating for weight loss.
I personally do not follow Keto, but being as popular as it is I thought I would still mention it.
A macro calculator can be extremely useful for Keto since Keto requires that you have high amounts of fat and low amounts of carbs, a macro calculator can help you determine what those numbers should be exactly.
If you are looking to keep track and make sure you stay within your macro goals and/or calorie goals, I’m a big fan of the MyFitnessPal app which makes it extremely easy to track both. As a side note, you can also track your weight loss progress, activity, and water intake in it as well.
I go more in depth on how to track your calories and macros for weight loss here.
Calories Burned Calculator
I mentioned earlier that a common problem I see when someone is struggling to lose weight is overestimating how many calories they’re burning.
Part of that problem is that cardio equipment is notorious for inflating how many calories are burned during a workout by up to 42%.
At least the equipment gives you some idea, but how are you supposed to have any idea how many calories you burned by walking, or jogging, or lifting weights even?
An activity, or calories burned, calculator can help give you a better idea.
As far as weight loss calculators are concerned, the calorie calculator and this calculator can work hand in hand to give you a ton of insight on your weight loss journey.
You input your current weight, the activity, and how long your workout was and it will give you an approximate amount of calories you burned during that workout.
Unfortunately, it’s still not entirely accurate, but for more information on how to more accurately calculate how many calories you burned during a workout, check out this article.
You have probably heard the term BMI before, it’s thrown around quite a bit when talking about weight.
BMI stands for Body Mass Index. It is a measure of your body fat based on your height and weight.
Based on your height, weight and the BMI formula, it will place you in a fitness category.
BMI categories can differ based on what company made them, but it is some variation of underweight up to obese.
That is the problem with BMI, it is only based on your height and weight.
It doesn’t actually consider your body composition and how much of that weight is muscle.
This can lead to some very inaccurate labels. For example, someone with a lot of muscle mass could easily get labeled as obese.
How BMI is Calculated:
If you know your weight in kilograms, the formula is your weight divided by your height squared.
If you use the imperial system, the formula is your weight times 703, divided by your height squared.
A BMI calculator is almost unnecessary, because you can easily find out what your BMI score is by looking at a BMI chart.
I mentioned a common problem with the BMI calculation is that it can easily mislabel someone with a high muscle mass.
Part of that is because the majority of BMI charts and calculations do not even take into account whether it is for a male or female.
Males generally carry more muscle mass, while females need to carry more fat.
For that reason, here are two separate charts one adult BMI chart and one specifically showing BMI for women.
BMI chart for women
Body Fat % Calculator
A body fat percentage calculator is just as the name sounds, a measure of what percentage of your body weight comes from fat.
It’s important to note here again that women biologically carry more fat than men.
Essential fat for women is considered 10%-12%, while men can go as low as 2%-4%.
That’s essential, meaning it’s dangerous to go anything below that.
Women’s body fat percentage can be as high as 24% and still be in the “fitness” categorization, while men can get up to 17% and still fall into it.
There are quite a few different ways to measure body fat, some of them aren’t very accurate, such as scales that claim to measure body fat. The most accurate way to measure your body fat percent is to get a Dexa Scan or to go to a facility that offers Hydrostatic Underwater Weighing.
For the sake of this post, we’ll just focus on the Body Fat Percent Calculations.
Body fat calculators can essentially use 2 different methods, skin folds or measurements.
Measuring your body fat percentage based on skin folds requires a tool called calipers, like these:
If you don’t have that tool, you can simply use a flexible tape measure and input the measuresurements of your neck, wasit, and hips into the calculator to get a good idea of your body fat percentage.
Body fat can be difficult to measure accurately, especially if you want something that is easily accessible.
It’s not exactly convenient to have to find and pay a facility to dunk and weigh you underwater just to figure out how much of your body composition is fat.
The body fat calculator will provide plenty of accuracy for the majority of the population. There isn’t a need to go to the trouble for anything more accurate unless you are competing for an athlete of some kind.
You can actually get a pretty good idea of your body fat percentage just be looking in a mirror. Thanks to Legion Athletics for these great body fat comparison pictures.
BMR Calculator or Basal Metabolic Rate Calculator
I mentioned BMR when talking about how the calorie calculator works and I promised I’d visit it in more depth, so here we are.
BMR stands for Basal Metabolic Rate. It’s a number that represents how many calories your body needs just to live. Think of it as the amount of calories you would burn if you laid in bed ALL day and literally did not move.
Basal Metabolic Rate Calculators use your gender, age, height, and weight to come up with his number.
Here is the formula for calculating your BMR:
For women: BMR = 655 + (4.35 x weight in pounds) + (4.7 x height in inches) – (4.7 x age in years)
For men: BMR = 66 + (6.23 x weight in pounds) + (12.7 x height in inches) – (6.8 x age in years)
You might be thinking, “What good does the number of calories I burn laying in bed do when I’m trying to lose weight?!”
Fair point, and on it’s on, not a ton.
But here’s why it’s important – you never want to eat below this number.
Sometimes people are so desperate to lose weight, they think the answer is to just cut as many calories as possible.
That is eventually going to backfire.
If you eat too few calories, your body will go into ‘starvation mode’ wanting to hold on to fat and burn as few calories as possible.
The other reason why you care about your BMR, like I mentioned in the calorie calculator section, is that your BMR is used to be multiplied by a fixed amount based on your daily activity level to determine how many calories you’re burning in total for an average day.
How Do You Calculate How Many Calories You Burn in a Day?
This total number of calories is referred to as your TDEE, or your Total Daily Energy Expenditure.
Notice above that I said an average day.
That’s because this will only tell you what you typically do. It won’t know and doesn’t take into account any extra activity you do.
When you’re trying to lose weight, a typical caloric goal is to intake 20%-25% fewer calories than your TDEE.
If your TDEE comes out to be 2000 calories and your goal is weight loss, you’ll be aiming to eat between 1500 and 1600 calories.
Here are the values to multiple your BMR by to calculate your TDEE:
- Sedentary (little to no exercise + work a desk job) = 1.2
- Lightly Active (light exercise 1-3 days / week) = 1.375
- Moderately Active (moderate exercise 3-5 days / week) = 1.55
- Very Active (heavy exercise 6-7 days / week) = 1.725
- Extremely Active (very heavy exercise, hard labor job, training 2x / day) = 1.9
I put this section below the calorie calculator, because if you don’t care to get into the nitty gritty and understand all of the definitions, you don’t really need to care about any of this because the calorie calculator will do all of the work for you.
And now you’re thinking you wish I mentioned that at the beginning before you read all of this.
Maybe. But now you’re smarter for it, so you’re welcome!
Weight loss calculator by percentage
Comparing pounds lost isn’t exactly apples to apples because everyone’s body type, composition and height are different.
Losing 10lbs might be a lot for one person, and a relatively small amount for another.
For this reason, you may want to calculate your weight loss in percentages.
A weight loss percentage calculator not going to help you much in the way of actually losing weight, but it will help you measure your progress by telling you what percentage of body weight you’ve lost so far during your weight loss journey.
How to calculate weight loss by percentage:
To calculate your weight loss percentage use this formula: divide the amount of pounds you’ve lost by your starting weight then, multiply the result by 100.
(5lbs / 150lbs) * 100 = -3.33%
So, if your starting weight is 150lbs and you lost 5lbs, you’ve lost 3.33% of your body weight.
How Weight Loss Calculators Work
Now you understand how we get to all of these numbers, but if your a fitness nerd like me, you might be wondering why and how we decided how many calories to eat and how we what works.
The answer is pretty simple.
It takes 3500 calories to burn 1 pound of fat.
Most experts recommend losing 1-2 pounds per week for sustainable and healthy weight loss.
That means, every day you need to burn 500 calories more than you eat to lose that pound at the end of the week.
Again, just like all of the calculators, these are just general rules and based on averages, but it gives your a good starting point and basis for understanding where it all comes from.
How Accurate are Weight Loss Calculators?
The accuracy of weight loss calculators is somewhat relative, and it depends.
If you had no idea at all how many calories you were burning before or no idea how many calories you should be aiming to eat, then they’re pretty good.
It also depends on your lifestyle and workouts.
If you do relatively the same things everyday and do about the same amount of activity, then they will also work pretty well for you.
On the other hand, for someone like me, they give me a great base to work off of, but if I really want to be accurate, I need something more.
This is because the amount of calories I burn in a day can vary pretty drastically.
I sit at a desk for the majority of the day, burning almost no calories, that’s pretty much always the same.
But my workouts change a lot.
Some days I will go run 5 miles, sometimes I will do nothing but lift weights, some days I do 3 hours of MMA training, and of course, at some point I have to take a rest day.
That means on any given day, I can burn anywhere from 1600-3000 calories.
That’s a huge difference.
Meanwhile, a weight loss calculator is going to be telling me the same number every day.
A More Accurate Solution
Weight loss calculators are a great place to start, especially if you were going in blind before, but if you hit a plateau or are really looking to take it to the next level, you might want to try something a but more accurate.
There are lots of fitness tracker options out there, but the important thing is that it has a heart rate monitor. That will give you a much more accurate number.
If it doesn’t have a heart rate monitor, it will be able to take in your steps, but essentially won’t be much better than the calories burned calculator.
The heart rate monitor paired with the movement tracker is what allows it to know that you are putting that extra work in and how much!
I generally follow the 20% less calories than my TDEE number when I’m trying to cut fat, but on the 3000 calories burned days, I definitely will eat a few more calories as well!
What 100 Calories Look Like As Food
We’ve talked a LOT about calories in this article.
I thought it would be fun to give you an idea of what 100 calories worth of different foods actually looks like to give you a reference point.
You’re welcome in advance for my amazing photoshop skills on the donut!
- 1 banana ~= 100 calories
- ⅕ of a dunkin donuts glazed donut ~= 100 calories
- .625oz of cheetos ~=100 calories
- 1.25 slices of bread ~= 100 calories
As you can see, not all calories are created equally. These are a great example of why macros are so important.
What It Takes to Burn 100 Calories
As mentioned in the calories burned calculator section, this will just be an average, but just to give you an idea (these are based on a person with a weight around 150lbs):
- 100 jumping jacks will burn about 100 calories
- Walking at an average pace for about 15 minutes will burn about 100 calories
- Running at an average pace will burn about 100 calories
- 25 minutes of weight lifting will burn about 100 calories
As always, anything I mention here is based on my own experience and learning, so always consult your doctor before making any diet or exercise changes.
If you have any questions or feedback, leave a comment or reach out to me on Instagram!