AC Tonnage Calculator
Find the right air conditioner size for your home.
AC Tonnage by Home Size
Zone 3, average insulation, moderate sun, 8' ceilings
| Sq Ft | BTU | Tons | Unit Size |
|---|---|---|---|
| 800-1,000 | 18,000-22,000 | 1.5 | 18K mini-split or 1.5-ton central |
| 1,000-1,300 | 22,000-26,000 | 2.0 | 24K unit / 2-ton central |
| 1,300-1,700 | 26,000-34,000 | 2.5 | 30K unit / 2.5-ton central |
| 1,700-2,100 | 34,000-42,000 | 3.0 | 36K unit / 3-ton central |
| 2,100-2,700 | 42,000-52,000 | 3.5-4.0 | 48K unit / 4-ton central |
| 2,700-3,300 | 52,000-60,000 | 4.0-5.0 | 60K unit / 5-ton central |
How We Calculate This
This ac tonnage calculator uses established formulas and industry-standard data to provide accurate estimates.
- Enter your specific values into the calculator fields above
- Our algorithm applies the relevant formulas using your inputs
- Results are calculated instantly in your browser — nothing is sent to a server
- Review the detailed breakdown to understand how each factor affects your result
These calculations are estimates based on standard formulas. For critical decisions, always consult a qualified professional.
How to Convert Oven Recipes to Air Fryer
This calculator estimates AC tonnage using a modified Manual J approach, starting with a base BTU-per-square-foot value adjusted for climate, insulation, sun exposure, ceiling height, and occupancy.
The basic rule:
- Base cooling load: approximately 20 BTU per sq ft for Zone 3 (adjusted by climate zone)
- Climate factor: Zone 1-2 (hot) adds 10-20%, Zone 4-5 (cool) reduces 10-20%
- Insulation factor: poor insulation adds 30%, excellent insulation reduces 20%
- Sun exposure: heavy sun adds 10%, light/shaded reduces 10%
- Ceiling height: add 10% per foot above 8 feet; each occupant above 2 adds 600 BTU
- 1 ton of cooling = 12,000 BTU/hr
This is an estimate. For accurate sizing, a Manual J load calculation performed by an HVAC contractor is recommended. Oversized AC units short-cycle (reducing dehumidification and efficiency), while undersized units run constantly without reaching set temperature.
When Would You Use This Calculator?
This ac tonnage calculator is designed for anyone who needs quick, reliable estimates without complex spreadsheets or professional consultations.
- When you need a quick estimate before committing to a purchase or project
- When comparing different options or scenarios side by side
- When planning a budget and need to understand potential costs
- When you want to verify a quote or estimate you've received from a professional
- When teaching or learning about the concepts behind these calculations
Frequently Asked Questions
How many tons of AC per square foot?
The general rule is 1 ton per 400-600 sq ft, but this varies hugely by climate and insulation. In hot Phoenix, you might need 1 ton per 350 sq ft. In mild San Francisco, 1 ton per 700+ sq ft. A proper calculation considers many factors beyond just square footage.
What happens if my AC is too big?
An oversized AC short-cycles — it cools quickly then shuts off before adequately dehumidifying the air. This leads to clammy, uncomfortable air, higher humidity, more wear on the compressor, higher energy bills, and a shorter equipment lifespan. Proper sizing is critical.
What is a Manual J calculation?
Manual J is the ACCA standard for residential HVAC load calculations. It accounts for insulation R-values, window U-factors, infiltration rates, duct losses, occupancy, appliance heat gain, and local weather data to determine the exact BTU load. It's more accurate than any rule of thumb.
How much does a new AC system cost per ton?
Central AC systems cost $3,000-$5,000 per ton installed (equipment + labor). A 3-ton system runs $9,000-$15,000 installed. Mini-split systems cost $2,000-$4,000 per ton. Equipment alone is $1,500-$3,000 per ton for quality brands.
What SEER rating should I get?
The federal minimum is SEER2 13.4-15.2 depending on region (as of 2023). We recommend SEER2 16+ for moderate climates and SEER2 18+ for hot climates. Higher SEER costs more upfront but saves 20-40% on cooling costs vs minimum-efficiency units.
Should I get a heat pump or AC?
Heat pumps provide both cooling and heating and are 2-3x more efficient than furnaces for heating in mild climates (above 30°F). In cold climates, a dual-fuel system (heat pump + gas furnace backup) is ideal. In hot climates where heating is minimal, a standard AC may suffice.