Calorie Calculators: The 2 Mistakes You’re Probably Making

A reader recently asked me the following question…

“I’m using a calorie calculator to figure out how many calories I need to eat to lose weight. My question is, should I use this same calculator to recalculate my calories whenever my progress stalls? And then use it again when I finish losing weight and want to go back to maintenance or into a surplus to build muscle?”

No, no, and no.

Let me clear something up about calorie calculators.

In fact, let’s make this a fun little DOs and DON’Ts thing.

I call it…

Calorie Calculator DOs and DON’TS

DO: Use a calorie calculator when you’re first starting out to help you come up with an estimated starting point for how many calories you need to eat per day for your goal (losing weightbuilding muscle, etc.).

DON’T: Use a calorie calculator for literally anything else ever again.

What I mean is…

  • Don’t use a calorie calculator to make adjustments when your progress stalls.
  • Don’t use a calorie calculator to find your new maintenance level at the end of a fat loss or muscle building phase.
  • Don’t use a calorie calculator to figure out how many calories you need to eat to get into a surplus after being in a deficit (or vice versa).
  • Don’t use a calorie calculator with the intention of getting a number that will be 100% perfectly accurate for you.

Here’s why.

1. It’s Always Just An Estimate

All calorie calculators, no matter how accurate they claim to be, are nothing more than a quick and easy way to come up with some kind of estimated starting point for what your calorie intake should be.

And while we all hope this estimate is the super accurate number we need, it’s usually not.

Don’t get me wrong. It could sometimes be kinda close, which would would be fantastic, as “kinda close” is the most realistic best-case scenario you could hope for.

But it could just as likely be hundreds of calories off.

And that’s enough to put you at maintenance or even into a surplus rather than the deficit you’re aiming for (or vice versa).

That’s why you need to think of calculators only as a tool for getting an estimated starting point, not a tool that will tell you for sure what calorie intake is guaranteed to work for you.

Here’s A Problem Calorie Calculators Cause

Because what ends up happening – and I’ve seen this many times – is that someone will use some calculator to figure out they need to eat 2000 calories a day to lose weight (just an example).

And they’ll assume this is a magical all-knowing calculator that can’t possibly be wrong, therefore 2000 is definitely the right calorie intake for them.

So they’ll start eating 2000 calories a day for a couple of weeks and then… nothing.

No weight loss. No progress. No anything.

This person will then say “I tried counting calories but it didn’t work!” Or, even worse, “I tried counting calories but it didn’t work, so this proves that weight loss isn’t really about calories after all!”

And then they’ll switch to some myth-based diet that also claims weight loss is about something other than calories (like the low carb diet), and they’ll continue not making any progress with that diet either.

The Estimate Wasn’t Accurate

In reality, of course, weight loss is always about calories.

So why didn’t this person lose weight even though they ate the amount the calculator said they needed to eat to lose weight?

Well, assuming they actually ate that amount in the first place (fun fact: most people eat more than they realize, which is a common problem I cover here: Why Am I Not Losing Weight?), the problem is that the calorie intake this calculator gave them simply wasn’t accurate.

If no weight loss happened, it’s guaranteed proof that the estimate was higher than it needed to be, and a deficit didn’t exist.

And when a deficit doesn’t exist, weight loss doesn’t happen.

How To Make It Accurate

Luckily, this is an easy problem to fix.

All you need is some trial and error, and a little patience. Specifically…

  1. Eat the amount of calories the calculator estimates for you, and track what happens with your body weight over the next 3-4 weeks.
  2. If it’s doing what you want it to do, you’re good. Keep eating that amount.
  3. But if it’s not, make a small adjustment (e.g. 250-500 calories at a time), track your body weight over the next 3-4 weeks, and see what happens then.
  4. Is your weight doing what you want it to do? If so, awesome. If not, repeat this process again until it is.

Whether we like it or not, this is the one and only way to find the accurate calorie intake we need.

Calorie calculators are only useful for giving us that initial estimated number to start with at the beginning of the process.

Which brings me to my next point…

2. You Only Need A Calculator ONE Time

Once you’ve used a calorie calculator one time to come up with your estimated starting point, you’re officially done using calorie calculators.


Because now you’re going to be eating this estimated amount of calories consistently, and you’re also going to be tracking what your body weight does over time when eating this amount.

And it’s this data that’s going to be the key to everything you need to know going forward.

This data is what you’re going to use to accurately find your new maintenance level, and make adjustments when progress stalls, and literally any other change you need to make to your calorie intake from this point on.

How To Use Your Real-World Data

So instead of relying on a calculator, you’re going to adjust your current calorie intake based on what your weight is or isn’t doing at the time in the real world.

For example, if you’re trying to lose weight and you’re eating 2500 calories a day but your weight has been the same for a month… you don’t need a calculator to come up with the “right” amount of calories for you.

You just need to eat 250-500 calories less than the 2500 you’re currently eating.

Simple as that.

Here’s another example.

Need to find your new maintenance level after a fat loss phase? Increase your calorie intake by about 250 calories for every 0.5lb you’re losing per week at the time.

So if you’ve been losing 1lb per week for the last 4 weeks, you’d increase your daily calorie intake by about 500 calories to get pretty close to your new maintenance level.

(Why? Because there are approximately 3500 calories in 1 pound of fat, and 500 more calories per day x 7 days = 3500.)

These are still just estimates, and they may sometimes still require additional adjustments based on what does or doesn’t happen.

But, it’s going to be significantly more accurate than any calorie calculator you find.

Which is why using a calorie calculator to come up with an estimate when you already have MUCH MORE ACCURATE real-world data available is like putting training wheels back on your bike after you already learned to ride it.

It’s something to do when you need help getting started. But once you’ve gotten started, it’s not something you ever need to do again.

What’s Next?

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