Learn the basic calculations used in the NICU every day

This one’s for all the folks out there who want to understand some of the calculations that are used to keep babies healthy and strong in the NICU. Truthfully, you don’t need to know how to do all of this when your baby is in the NICU – the doctors and nurses will manage these calculations for your baby – but many parents like to know how anyway.

So, if you want to give it a try, grab your calculator, and start crunching some numbers with me!

Basics

We NICU nurses talk a lot about fluid volumes in the NICU, like ML’s and CC’s, and a lot about weights, like grams, kilograms, pounds, and ounces.

Let’s look at what we’re talking about.

When we talk weight, you’ll usually hear about grams & kilograms or pounds & ounces.

When we talk fluid amounts (think milk or medicines), we generally use the terms Milliliters – or ML’s – and CC’s.

Here’s one simple basic every parent will learn early on the journey:

Did you know that 1 Mililiter (ML) = 1 CC = 1 gram? Yep, they’re essentially interchangeable (*see annotation). So when you hear one nurse say “Your baby is eating 25 ML’s” and then the next nurse says “Your baby took 15 CC’s from the bottle” now you know that ML’s and CC’s are equal amounts.

Another quick and easy one to know is that 1 kilogram is the same as 1000 grams. So a 2.3 kilo baby weighs 2300 grams. (2.3 X 1000)

Some more basic weights and measures that help put things in perspective:

5 grams = 1 teaspoon

15 grams = 1 Tablespoon

30 ml = 1 ounce

Weight Conversions

Let’s take a look at converting weight from the metric system, which most hospital staff use, and the Imperial System which we recognize as pounds and ounces.

1 kilogram = 2.2 pounds

1 pound = 0.45 kilograms

Let’s do an example – kilograms to pounds

If your preemie weighs 3.8 kilograms, you’d multiply 3.8 x 2.2, and the weight = 8.36 pounds (That’s a pretty big preemie!)

Want to calculate the other direction?

Example – Pounds to kilograms

If your preemie weighs 1.8 pounds, you’d multiply 1.8 x 0.45, and the weight = 0.81 kilograms.

(If you multiply this kilogram weight by 1000, you have the weight in grams. In this case, 0.81 kilograms is 810 grams.)

Nutrition Calculations

Doctors and dietitians are calculating how many calories your baby needs every day. Whether the calories come from IV fluids or from breast milk, they’re always based on your baby’s weight, so the amounts change frequently as your baby grows.

Of course, each baby is unique and each doctor has a different approach to calorie management. Typically, babies need 100 calories – 150 calories per kilogram of weight each day. (Every baby is different, so ask your NICU to better understand what calculations they are using).

Here’s another example:

Your baby weighs 2.4 kilograms

If the doctors want your baby to have 120 calories per day per kilogram, you’d multiply 2.4 kg X 120 = 288 calories per day

So, what does this mean for how much milk your baby needs?

Typically, breast milk and standard formula have 20 calories in every ounce. So let’s calculate how much milk your baby needs.

If your baby weighs 3.4 kilograms, can you do the math to figure out that he needs 408 calories in a 24 hour period? ( see example above – 3.4 kg x 120 = 408)

If he is fed every 3 hours, that equals 8 feedings each day. So if you divide those 408 calories your baby needs each day into 8 feedings, you get 51 calories per feeding. (408 ÷ 8 = 51)

If he’s eating plain breast milk, which has 20 calories per ounce, divide the number of calories for each feeding by 20, and you’ll figure out how many ounces of milk your baby needs. In this example, 51 calories divided by 20 calories per ounce equals 2.55 ounces. (51 ÷ 20 = 2.55)

But wait a minute, that’s a whole lot of milk – can you calculate how many cc (or ml) that is? Remember, 1 milliliter (ml) = 1 gram (g) = 1 cc, and there are 30 ml in every ounce. So 2.55 ounces is the same as 76.5 ml. (2.55 x 30 = 76.5)

For those of you with preemies, you know that’s a pretty darn big feeding. What if your baby’s stomach can’t handle so much volume?

Fortifier Calculations

Most NICUs add calories to milk or formula with fortifiers, so that there are more calories in every ounce. Rather than 20 calories per ounce, they’ll add fortifier to make it 22 calories per ounce – or 24 calories, 26 calories, and even higher if needed. They’ll do this with powdered, liquid or Prolacta fortifier.

Let’s now calculate how many ounces your baby needs to take every feeding IF your baby’s milk is being fortified to 24 calories per ounce. In order to get his 51 calories every feeding, he needs only 2.1 ounces of milk every feeding. (51 ÷ 24 = 2.1) That’s 63 ml. (2.1 X 30)

Or if his milk is fortified to 28 calories per ounce, he needs only 1.8 ounces of milk every feeding (51 ÷ 28 = 1.8). That’s 54 ml. (1.8 X 30)

So that’s one major reason why NICU’s fortify milk – many babies need a smaller amount of milk in their tummies since their tummies are so small. But they still need those calories to grow! So they fortify the milk based on calculations like these.

Temperature Calculations

Normal body temperature for a baby is 37.0 degrees Celsius, or 98.6 degrees Fahrenheit. It’s the same for preemie babies and full-term babies alike. How do you convert from one to the other? Honestly, it’s pretty darn easy to do with online converters. But if you want to do it yourself, here’s how:

If you have a temperature in Fahrenheit and you want it in Celsius, subtract 32 from the temperature in Fahrenheit, and then multiply by 5/9.

(Temp[F] – 32) x 5/9 = Temp[C]

Example:

If the temp is 99.2 in Fahrenheit

99.2-32= 67.2. Then take that 67.2 x 5/9 = 37.3

So 99.2 F = 37.3 C

You can reverse this if you have the temperature in Celsius and want to know Fahrenheit (and this is more commonly what parents in the US want because we’re used to Fahrenheit and those darn doctors and nurses often use Celsius).

(Temp[C] x 9/5) + 32 = Temp[F]

Example:

If the temp is 38.1 in Celsius

38.1 x 9/5 = 68.6. Then take that 68.6 + 32 = 100.6

So, 38.1 Celsius = 100.6 F (And this is a fever for a newborn!)

Congrats

You can now do some of the basic NICU conversions and calculations. If you’ve read along this far, you’re probably actually interested in doing the math, so print this sheet out and fill it in with your baby’s numbers – you’ll start to better understand what the numbers mean and why the NICU is doing what they’re doing.

Bonus points – You may be able to stump your nurses and doctors with this trivia – ask them if they know what CC stands for. I know it wasn’t something I remembered until I looked it up for this article! Answer = Cubic Centimeter

*To be clear, cc and ml are measures of volume and grams are a measure of weight. Since most of what we measure in the NICU (formula, IV fluids, body fluids) is mostly water, this is close enough and they are essentially equal. But the fact is that 1 cc (or ml) = 1 gmonly for water at 4 degrees C.