Why Coverage Is a Range and Not a Number
Every row above gives square footage as a span rather than a figure, and the span is wide on purpose. A 3 ton unit covers 1,400 sq ft in one house and 1,900 in another, and both are correct.
Climate does most of that work. The same house needs materially more cooling on the Gulf coast than in the upper Midwest, so the low end of each range is the hot and humid answer and the high end is the northern one. After climate, the things that move it are insulation quality, window area and orientation, ceiling height, how many people live there, and whether the house is one storey or two.
Use the table to understand what a size means, not to pick one. If you already own a system and just want to confirm its size, you can read the tonnage off its model number. If you are choosing rather than checking, run the actual numbers with the AC tonnage per square foot calculator for a whole house, or the HVAC load calculator for a room-by-room load. Roughly half of installed systems are oversized, and the cost of guessing high is paid every month afterwards.
The same caveat applies to the price column, and it is worth stating plainly because a single dollar figure looks more certain than it is. Each price above is a national midpoint for a straightforward like-for-like swap at a mid efficiency tier. Three things move it a long way in either direction: the efficiency tier you pick, which can add close to half again on the equipment; your region, since the same job runs materially more in high-cost metros than in the rural south; and whether any ductwork or electrical work is needed, which is the line item that most often separates two quotes for what looks like identical work. To put your own numbers against a size, the central air installation cost calculator breaks a central AC job into those line items, and the installation and replacement cost calculators cover the other jobs if the furnace or the ductwork is changing at the same time.
1.5 Ton AC Unit
The smallest standard central size: about $4,500 installed, moving 600 CFM through a 12-inch supply trunk and drawing roughly 1,440 watts, or 6 amps at 240V. It suits about 600 to 950 sq ft depending on climate. At this size the honest question is whether central air is the right product at all. A small house, a large apartment or a finished basement in this range is often better served by a ductless head, which avoids running ductwork for a load this small.
2 Ton AC Unit
Two tons costs about $5,000 installed, needs 800 CFM through a 14-inch supply and a 16-inch return, and pulls around 1,920 watts at 8 amps - a fit for about 900 to 1,300 sq ft. This is the size people most often discover they already have and then start doubting, usually after one hot week. Before concluding it is undersized, check the ductwork and the air sealing: a 2 ton unit struggling in a 1,100 sq ft house is far more often a duct or infiltration problem than a capacity one. Note that air conditioning units 2 ton and up are all sold on the same nominal scale, so a 2 ton air conditioner from one maker and another from a different one cover the same load even when the cabinets look nothing alike.
2.5 Ton AC Unit
Roughly $5,500 installed, moving 1,000 CFM through a 16-inch supply and drawing about 2,400 watts, 10 amps - a fit for about 1,150 to 1,600 sq ft. Two and a half tons is the usual answer for a mid-size single-storey home, and it is the step where ductwork starts mattering more than tonnage. It is also the size most often skipped in a quote, because a contractor who stocks 2 and 3 ton units will tend to push you to whichever is on the truck.
3 Ton AC Unit
The most common central AC size in American homes: about $6,000 installed or $79 a month financed, 1,200 CFM through a 16-inch supply and an 18-inch return, drawing 2,880 watts at 12 amps. It suits about 1,400 to 1,900 sq ft.
Being the default size is exactly the problem with it. A 3 ton air conditioner is what gets quoted when nobody has run a load calculation, so it is both the most correct size in America and the most frequently wrong one. Its startup surge of 8,600 to 14,400 watts is also the point where generator backup stops being simple, which is why soft-start kits are most often fitted at this size.
3.5 Ton AC Unit
Roughly $6,700 installed, needing 1,400 CFM through an 18-inch supply and a 20-inch return, drawing 3,360 watts at 14 amps - and covering about 1,650 to 2,250 sq ft. This size does not exist in every product line, which is why some quotes jump straight from 3 to 4 tons. It is worth asking for specifically, because taking the 4 ton instead means paying more up front and then running an oversized system for its whole life.
4 Ton AC Unit
Four tons runs about $7,400 installed, moving 1,600 CFM through a 20-inch supply and a 22-inch return, drawing 3,840 watts at 16 amps - a fit for about 1,900 to 2,600 sq ft. The ductwork is the constraint that bites here. Plenty of houses that could use 4 tons have trunks sized years ago for 3, and dropping the larger unit onto the smaller duct produces register noise and starved far rooms rather than more cooling. A two-storey house of this footage also usually does better with zoning than with one larger system.
5 Ton AC Unit
The largest standard residential size: about $8,500 installed, needing 2,000 CFM through a 22-inch supply and a 24-inch return, drawing 4,800 watts at 20 amps, and suiting about 2,400 to 3,300 sq ft. Above five tons you leave the residential product range and into light commercial equipment, which is why large houses are more often served by two systems than one bigger one. Two smaller units also give you zoning for free and mean a failure takes out half the house rather than all of it. If a contractor is quoting a 5 ton air conditioner for a house under about 2,400 sq ft, ask to see the load calculation before agreeing, because at this size an oversizing mistake is an expensive one to live with.
What the Ton Actually Measures
One ton equals 12,000 BTU per hour of cooling, so a 3 ton unit removes 36,000 BTU of heat every hour it runs. The name is a leftover from the ice trade: it is the cooling you would get from melting one ton of ice over 24 hours. It says nothing about the physical weight of the equipment, which is a reasonable thing to assume and a common source of confusion. If you need to move between the two units at any size, the ton to BTU converter lists every step.