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About Us

Alex David

Hi, I am Alex David, an HVAC specialist. Together with another HVAC expert and a team of developers, we want to stop people from choosing the wrong AC size. We built Tonnage Calculator AC to make finding the exact tonnage or BTU needs for your room incredibly simple.

How It Started: The 1.5-Ton AC & Short Cycling Story

One evening, our friend group was hanging out in one of our buddies' gardens. He told us a story about what he experienced last year when he bought the wrong size AC after moving into a new apartment.

He wanted to replace his old AC because it was very old and it was time for a replacement. So, he visited a local store to purchase a new air conditioner for his bedroom.

The salesperson suggested a 1.5-ton AC unit without asking critical questions about ceiling height, floor level, or sun exposure, which are actually very important. He followed his advice, but a problem arose. The unit was far too large for the space. The AC would cool the room in minutes and then shut off, and this cycle repeated all day. This is called "short cycling." Also, the room felt damp because the unit never ran long enough to properly dehumidify the air. When his electric bill came, he noticed a much higher electricity bill than ever before.

While searching for a solution on the internet, he discovered that HVAC engineers use a standard procedure called Manual J to size units. This method accounts for climate zones, insulation, sun exposure, and occupancy. While the math is manageable, it was mostly locked behind expensive software or complex technical manuals.

After consulting another HVAC specialist in our friend group, he moved the oversized unit to a larger room and installed a 1-ton unit in his bedroom.

Now it's a perfect fit for him. He shared this whole experience with the rest of us later on. Hearing how frustrating this process was, I knew my own HVAC background could help too. Since we were all already friends, including the developers, the two of us HVAC specialists, and him, we decided to team up and build this tool to help others avoid the same AC sizing mistake.

Decoding the AC Sizing Math for Everyone

As our entire team is a friend group consisting of developers, two HVAC specialists, and a friend who chose the wrong AC a year ago and became a self-taught HVAC enthusiast after his experience, we brought together different perspectives to solve a common problem. Drawing inspiration from ASHRAE guidelines and the Manual J methodology, we distilled the math down to the variables that actually matter for residential window, split, and mini split AC units.

We built a calculator that is accessible to everyone: no sign-ups, no paywalls, and no email lists. Just enter your room details and get an accurate recommendation instantly.

Our Mission is Saving You from the HVAC Guessing Game

We aren't here to replace professionals. For whole-building designs or specialized environments like hospitals, an engineer is essential. However, for millions of people simply trying to cool a bedroom, living room, or kitchen, professional consulting shouldn't be a barrier.

Tonnage Calculator AC bridges the gap between established engineering standards and everyday users. We take professional-grade math and make it usable for free.

Our goal is to save you from buying the wrong equipment, suffering from comfort issues, or wasting money on high energy bills. If we can help you make an informed decision, we've done our job.

Balancing Accuracy, Usability and Future

According to our testers, our calculator covers the variables responsible for roughly 90% of residential cooling loads: room dimensions, climate, ceiling height, occupancy, appliances, sun exposure, and insulation. For typical homes, this provides a highly reliable estimate.

To maintain simplicity, we currently exclude factors like specific wall materials or ductwork efficiency, which are more critical for commercial systems. We are constantly balancing engineering precision with user accessibility to ensure our tool remains easy to use without sacrificing quality.

Since this calculator is suitable for buying window, split, and mini split ACs, we are developing another tool which recommends tonnage and BTUs for portable air conditioners for home.

The Standards Behind Our Calculations

Our tool is grounded in industry-standard engineering principles, specifically:

  • ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) standards, followed worldwide.
  • ACCA Manual J, the standard procedure for residential load calculations used by licensed professionals.
  • Climate data sourced from meteorological databases that track regional temperature and humidity maximums.

For a detailed breakdown of our formulas, please visit our methodology page.

When to Consult a Professional

While our tool is excellent for single-room residential units, you should always consult a professional for the following:

  • Whole-house HVAC systems or multi-zone setups.
  • Commercial or industrial spaces.
  • Critical environments like server rooms, labs, or hospitals.
  • Buildings with non-standard construction or complex ductwork.
  • New construction requiring compliance with specific building codes.

In these cases, an engineer is required to ensure safety and performance.

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