What is a 'Ton' in AC terms?

A ton of air conditioning is 12,000 BTUs (British Thermal Units) per hour. It represents the amount of heat absorbed by melting 1 ton of ice in 24 hours.

How many tons in a BTU?

There are 12,000 BTU per ton of refrigeration (TR). To convert BTU to tons, divide your total BTU/hr by 12,000. For example: 24,000 BTU/hr / 12,000 = 2 tons.

How does this calculator determine the required BTU?

The calculator starts with a base of 35 BTU per square foot of floor area. It then adjusts for ceiling height (adding 10% per foot above 8 ft), occupancy (adding 500 BTU for each person beyond 2), and sun exposure (multiplying by 1.1 for sunny rooms or 0.9 for shaded rooms). The final BTU figure is divided by 12,000 to give tonnage.

How does sun exposure affect AC size?

Sun exposure significantly impacts the heat load of a room. A room with heavy direct sunlight absorbs more heat, requiring about 10% more cooling capacity. Conversely, a well-shaded room needs about 10% less. This calculator applies a ×1.1 multiplier for sunny rooms and ×0.9 for shaded rooms.

How many BTU is a 2.5-ton AC unit?

To convert tons to BTU, multiply the tonnage by the standard conversion rate: 1 ton = 12,000 BTU/hr. So a 2.5-ton AC unit provides 2.5 × 12,000 = 30,000 BTU/hr of cooling capacity.

AC Tonnage Calculator

Want to learn how to calculate AC tonnage for your home, office, or commercial space? Whether you're sizing a new system or upgrading an old one, our all-in-one AC tonnage calculator takes the guesswork out of the process.

Complete User Guide

Our AC Tonnage Calculator estimates the right cooling capacity for your room in seconds. Here's how to use it:

Step 1: Enter your room's length and width in feet.

Step 2: Enter the ceiling height in feet (leave blank to use the standard 8 ft default).

Step 3: Enter the number of people who typically occupy the room (defaults to 2 if left blank).

Step 4: Select the sun exposure level — Shaded, Normal, or Sunny — based on how much direct sunlight the room receives.

Step 5: Click Calculate to instantly see the recommended BTU/hr and AC tonnage for your space.

The Mathematical Formula

BTU = (Area × 35) × Height Adj × Occupancy Adj × Sun Adj; Tonnage = BTU ÷ 12,000

This calculator uses a residential load estimation formula based on floor area and environmental adjustments.

Base BTU = Room Area (sq ft) × 35

Height adjustment: if ceiling height > 8 ft, multiply BTU by (1 + (height − 8) × 0.1) Example: a 10 ft ceiling adds a 20% increase → BTU × 1.2

Occupancy adjustment: add 500 BTU for each person beyond 2 Example: 4 people → add 1,000 BTU

Sun exposure adjustment: - Sunny room → BTU × 1.1 (+10%) - Normal room → no change - Shaded room → BTU × 0.9 (−10%)

Tonnage = Final BTU ÷ 12,000 (1 ton of refrigeration = 12,000 BTU/hr)

About AC Tonnage Calculator

Why tonnage matters in AC sizing? When choosing the right air conditioner, tonnage is the most important factor to consider — and knowing how to calculate AC tonnage can save you from poor comfort and high energy bills. In simple terms, tonnage refers to an AC unit's cooling capacity, and it determines how effectively your system will cool a given space.

One ton of refrigeration (TR) equals 12,000 BTU (British thermal units) per hour, or the amount of heat needed to melt a ton of ice in 24 hours. For example, a 2-ton AC unit can remove enough heat to melt 2 tons of ice per day. That's why bigger rooms need more BTUs, and thus more tonnage.

Choosing the wrong tonnage can lead to problems: - Too little, and your AC will run constantly without fully cooling the space. - Too much, and it will cool the room too quickly, leaving it cold and damp.

That's why using an AC tonnage calculator — especially one based on AC tonnage per square foot and standard HVAC load guidelines — is so important.

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