HVAC Excel Calculators (User Guide Included)

I’ve always wanted to download HVAC excel calculators to assist my design calculations. But, I couldn’t find a single one that is easy enough for me to understand and use. So, I’ve always ended up deleting them. Since nobody can let me download a useful one, I had to make myself one.

For more than 7 years of working in the HVAC industry from being a project engineer to becoming a project manager, I developed 8 HVAC excel calculators. They helped me to perform design calculations such as chilled water pipe sizing and grille sizing.

Ever since I had my HVAC excel calculators, I noticed that I became much more efficient and productive. My colleagues often took 2-3 hours to finish their sizing work while I’ve done it in less than an hour. This allows me to move on to other things and produce more results.

“Excel calculators allow me to free up time to focus on important things that matter the most.”

Yu Chang Zhen

Developing these excel calculators is not an easy task. Not only that I need to know how to do the calculation in the first place, but I also need to test and refine the results through construction projects. Basically, it took me a few years to put together the excel calculators.

Table of Content

1. Chilled Water Pipe Sizing Calculator

The first and my favourite excel calculator is the chilled water pipe sizing calculator. Among all the calculators, I use this calculator the most. It’s really been helping me to quickly find the corresponding chilled water pipe size based on the water flow rate.

I develop this chilled water pipe sizing calculator based on the friction loss chart method. If you don’t know how to find chilled water pipe size using a friction loss chart, I suggest you check out my post on how to size chilled water pipe size.

From the friction loss chart, I’ve set the friction loss and water velocity limit. So, all you have to do is to enter the water flow rate either in gpm, m3/hr or l/s and the calculator will show you the appropriate pipe size in mm and inch.

2. HVAC Grill Size Calculator

I remember I developed this HVAC grille size calculator because I was sizing almost a hundred units of return air grilles and external weather louvers. The manual way is quite simple but when you’re dealing with hundreds of grilles, it is so much better to use an excel calculator.

If you don’t know how to calculate grille size, check out my post on return air grille sizing guide where I included the exact grille sizing formula as well as three grille CFM charts for you to quickly find the suitable grille size.

The grille sizing formula involves airflow and the free area of the grille. With both values, you can calculate the required grille area and thus, match the grille size. For extra convenience, you can print out my grille CFM charts to match the grille area.

3. Cooling Tower Make-Up Water Calculator XLS

Sizing the cooling tower make-up water tank is relatively easy. However, many people don’t actually know how to size it. For the manual way, see my blog post on how to size cooling tower make-up water tank where I’ll walk you through the calculation process step by step.

From there, I translated the manual way to excel calculator. Sometimes, I need to change the operation hour and the tank size. Thus, this excel calculator is very handy.

By the way, you can speed up your design calculation process with my HVAC excel calculators. They are great for basic sizing and design. However, if you’re a design engineer, I encourage you to learn cooling load calculation as it is an extremely valuable skill to have.

RTS Cooling Load Calculation Course

Learn how to calculate cooling load using the ASHRAE’s Radiant Time Series method that accounts for solar heat gain, conductive heat gain, radiant heat gain and internal heat gain in a 24 hours load profile manner.

4. Pressure Drop in Pipe Calculator Excel

Pressure drop in pipes, valves and fittings is not easy to calculate. There are a few ways to do it but I find that the ASHRAE K factor method is the easiest and understandable way to estimate the pressure drop.

Again, if you have no idea how to calculate pressure drop in valves and fittings, I suggest you read my post on how to calculate pressure drop across a valve. I’ve included the ASHRAE pressure drop formulate in the post.

In addition to the formula, ASHRAE also split the calculation for threaded and flange valves and pipe fittings. However, ASHRAE didn’t discuss the required water velocity in the same section but I’ve included it in my excel calculator.

5. Flange Pressure Rating Calculator Excel

I’ve had a blog post about closed loop chilled water system pressure. If you haven’t read it, I encourage you to do so because it debunked the myth about flanges, valves and fittings pressure rating in the chilled water system.

Basically, many engineers calculate pressure ratings wrongly or allow too high of a safety factor thereby increasing the overall cost of the chilled water system. Not many engineers understand the stagnation pressure that I’ve mentioned in my blog post.

Using the static and dynamic pressure, we can calculate the stagnation pressure and thus, I brought the formula into excel and created the pressure rating calculator.

6. Staircase and Lift Pressurization Fan Calculator

Many engineers don’t know how to calculate the required fan airflow of staircase pressurization. I previously completed two projects that have the staircase pressurization system and thus, I refined the excel calculator based on my experience.

As for the lift lobby pressurization fan airflow calculation, the estimation of the number of doors open during a fire is critical. We use a minimum of 2 doors or 10% of the total doors whichever is higher to determine the required pressurization fan capacity.

7. Smoke Extraction Fan CFM Calculation

Although it is not difficult to calculate smoke extraction fan capacity manually, it is still very useful to have an excel calculator especially when you’re dealing with large-scale projects.

However, I only included the calculation for the basement carpark which is very common in HVAC construction projects. Almost every high-rise residential and commercial buildings required a basement smoke extraction system.


Many excel calculators out there are difficult and complicated to use. Hence, I designed these 7 excel calculators to be user-friendly which each calculator included a user guide. So, check out my Design Engineer Starter Pack now to see more about these excel calculators.

Again, consider using my HVAC excel calculators to ease your design work and learn how to use the latest (more accurate) RTS method to calculate cooling load and plot a 24 hours load profile for better equipment sizing and load optimization.

RTS Cooling Load Calculation Course

Learn how to calculate cooling load using the ASHRAE’s Radiant Time Series method that accounts for solar heat gain, conductive heat gain, radiant heat gain and internal heat gain in a 24 hours load profile manner.

If you have anything to add (or ask) about this topic, leave a comment down below!

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