Calorie Calculator Calibration

Calorie Calculator Calibration

What all web based calorie calculators do is *estimate* your BMR based upon various research that has been done. These research studies have come up with various formulas that you can use to estimate your calories, for example, two of the most commonly used equations come from the research done by Harris-Benedict in 1919 or Mifflin-St Jeor done in 1990. The Mifflin-St Jeor appears to be more accurate but my calorie calculator lets you choose either. These equations based upon the research are easy to use but only get you to within about +/-10% accuracy on the caloric estimation. This innovative calibration procedure lets you approach the accuracy of the expensive medical lab test with a simple web calculator. Here is the procedure:

  1. Using my calorie calculator, answer all the questions and set your goal in step 6. Scroll down and read off two very important numbers show below. First your predicted weight loss (or gain) for the month is shown circled on the right side. In this example, the predicted amount of weight loss is 5.4 pounds per month. The second important number is your daily caloric needs, in this example, 2694 calories.
  2. Calorie Calculator Example Output
  3. Now here is the tough part, you need to calorie count for a month and consume precisely the daily calories specified. There are many iPhone and Android applications that make counting calories very easy. Not only do they have barcode readers for grocery store purchased items but they have virtually all fast food items as well. Calorie counting is easy with these apps, but, you gotta enter everything you eat or drink! Cream in your coffee? Log it! Sugar in your tea? Log it!
  4. Weigh yourself daily for a month. Its important that you weigh yourself first thing in the morning after you go to the bathroom but before you eat or drink anything. Make sure to weigh yourself on the same scale for every measurement. Log your results in this weight logging spreadsheet which will do a best fit curve analysis to smooth out the inaccuracies in the scale readings as shown below:
  5. Charted Weight For Calorie Calculator Correction
  6. In the excel spreadsheet, read off where the line drawn by my software crosses the day=1 axis and the day=30 axis – this is your corrected weight gain/loss. In this example you can see the starting weight is 240.0 at day 1 and the ending weight is 230.5 pounds at day 30 – a loss of 9.5 pounds in 30 days. Notice how the best fit line smooths out the inaccuracies in the weight measurements.

Step 1: Enter weight change prediction from calorie calculator: pounds/month
Step 2: What does the straight weight line read at Day 1? pounds
Step 3: What does the straight weight line read at Day 30? pounds

Your Weight Loss pounds
Your Calorie Correction Factor calories/day

In the future, anytime you use my calorie calculator, enter you correction factor in step 9 as shown below. Make sure to include the minus sign if the correction is negative!

Calorie Calculator Calibration Example


The calibration procedure takes a month and I wont lie, its a lot of work. For most people, just using the equations that get you within 10% are close enough and its not worth the bother to calibrate. For serious bodybuilders though, having this accurate information is critical. Since serious bodybuilders are already methodically taking all the data required for this calibration, its not much work for them at all and the gain in accuracy makes a huge difference.

About this calibration calculation. You sharp readers will notice that I am using 3500 calories per pound – here is the equation I use:

Correction (cals/day) = ((Actual Weight loss(lbs/mo) – Predicted Weight loss(lbs/mo)) x 3500 cals/lb ) / 30days/mo

Wait, you say! Thats not accurate, a pound of fat has approximately 3500 calories but a pound of muscle doesn’t. Isnt using 3500 innaccurate? Not at all. Remember that gaining or losing muscle happens very, very slowly when compared to the gain or loss of fat. Its a very good approximation to say that all the weight difference in a month is due to fat; therefore, using 3500 calories per pound is a good estimation. If I wanted to make this even *more* complicated, I could force people to measure their body composition daily too so that I could accurately take into account both fat loss/gain and the muscle loss/gain. Given how people’s reluctance to use skinfold calipers I chose to do without this. If somebody wants this, I will add it.

By the way, for those of you who dont know what BMR is, its Basal Metabolic Rate, and it is how many calories you would burn off per day if you just did nothing – this is basically what calorie calculators estimate. The gold standard for measuring BMR accurately is a medical laboratory test where they measure the concentration of oxygen and carbon dioxide between your in your inhalation and your exhalation as well as the precise rate of breathing (liters per minute). From this they can calculate precisely how fast your body is burning calories. Obviously, using this test is the best way to calculate your BMR but I can’t afford it and I doubt you can either.