Skip to main content
Tonnage Calculator AC Logo

HVAC Utilities & Conversions

Beyond standard sizing, HVAC system design involves complex conversions, efficiency calculations, and airflow management. We've built these supplementary tools to assist homeowners and professionals alike.

HVAC Load Calculator

Manual-J-style whole-house heating and cooling load calculation with a printable line-by-line worksheet - the number every other sizing decision starts from.

Use Tool

HVAC CFM Calculator

Calculate airflow every way it comes up: room CFM from air changes per hour, system CFM per ton, duct capacity, the temperature-rise method, and metric conversions.

Use Tool

Air Changes per Hour (ACH) Calculator

Convert CFM to ACH and back, check air purifier CADR coverage, and see recommended air change rates from bedrooms to operating rooms.

Use Tool

Duct Size Calculator

Calculate the proper duct dimensions and airflow velocity needed to distribute conditioned air efficiently throughout your home.

Use Tool

SEER Energy Savings Calculator

Compare the long-term cost savings of upgrading to a higher SEER (Seasonal Energy Efficiency Ratio) air conditioner.

Use Tool

AC Wattage Calculator

How many watts does your AC use? Running watts, amps, startup surge, generator size, and electricity cost per hour and month - from real EER2 math.

Use Tool

Find AC Tonnage by Model Number

Already have an AC and want to know its size? Paste the model number from the data plate and our decoder reads the tonnage out of it instantly.

Use Tool

Ton to BTU Converter

Quickly convert HVAC cooling capacity from Tons to British Thermal Units (BTUs), or vice versa.

Use Tool

BTU to Watts Converter

Convert thermal energy (BTUs) to electrical power (Watts). Useful for determining the electrical requirements of portable or window AC units.

Use Tool

Understanding HVAC Terminology

The HVAC industry relies on a variety of specific measurements and ratings. Our conversion tools make it easy to translate these technical specifications into numbers you can understand.

What is a SEER Rating?

SEER stands for Seasonal Energy Efficiency Ratio. It measures the cooling output of an air conditioner over a typical cooling season divided by the total electrical energy input. A higher SEER rating means greater energy efficiency. Use our SEER Savings Calculator to see if the higher upfront cost of a premium unit is worth the long-term savings on your energy bill.

Tons vs. BTUs vs. Watts

  • BTU (British Thermal Unit): The traditional measure of heat. One BTU is the amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit.
  • Ton: In HVAC, a "ton" of cooling capacity equals 12,000 BTUs per hour. This historically referred to the amount of heat required to melt one ton of ice in 24 hours. Our Ton to BTU converter handles this translation instantly.
  • Watts: Electrical power is measured in Watts. Our BTU to Watts converter is particularly useful when you need to know if a window AC unit or portable cooler will overload a specific electrical circuit in your home.

Jump Straight to a Conversion

If you came for one specific conversion, these links go to the exact chart or section that holds it.

Why Duct Sizing Matters

Even the most perfectly sized, high-SEER air conditioner will underperform if it is connected to improper ductwork. Ducts that are too small restrict airflow, causing the system to work harder and increasing noise. Ducts that are too large will fail to maintain enough air velocity to push conditioned air to the furthest rooms in the house. The Duct Size Calculator helps estimate the required dimensions to maintain proper static pressure and velocity.